Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
In addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative value
thanks.
On Tue, Sep 13, 2022 at 09:09:47PM +0800, yong wrote:
Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
What is "this patch"? There is no context here :(
In addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative value
In what way? What should be done here by us?
confused,
greg k-h
Greg KH gregkh@linuxfoundation.org 于2022年9月13日周二 21:54写道：
On Tue, Sep 13, 2022 at 09:09:47PM +0800, yong wrote:
Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
What is "this patch"? There is no context here :(
Sorry, I forgot to quote the original patch. the patch is as follows
f27ce0e page_alloc: consider highatomic reserve in watermark fast
In addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative valueIn what way? What should be done here by us?
I think these two patches should also be merged.
The classzone_idx parameter is used in the zone_watermark_fast functionzone, and 3334a45 use ac->high_zoneidx for classzone_idx. "9282012 page_alloc: fix invalid watermark check on a negative value" fix f27ce0e introduced issues
confused,
greg k-h
On Wed, Sep 14, 2022 at 08:46:15AM +0800, yong w wrote:
Greg KH gregkh@linuxfoundation.org 于2022年9月13日周二 21:54写道：
On Tue, Sep 13, 2022 at 09:09:47PM +0800, yong wrote:
Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
What is "this patch"? There is no context here :(
Sorry, I forgot to quote the original patch. the patch is as follows
f27ce0e page_alloc: consider highatomic reserve in watermark fastIn addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative valueIn what way? What should be done here by us?
I think these two patches should also be merged.
The classzone_idx parameter is used in the zone_watermark_fastfunctionzone, and 3334a45 use ac->high_zoneidx for classzone_idx. "9282012 page_alloc: fix invalid watermark check on a negative value" fix f27ce0e introduced issues
Ok, I need an ack by all the developers involved in those commits, as well as the subsystem maintainer so that I know it's ok to take them.
Can you provide a series of backported and tested patches so that they are easy to review?
thanks,
greg k-h
Here are the corresponding backports to 4.19. And fix classzone_idx context differences causing patch merge conflicts.
Jaewon Kim (2): page_alloc: consider highatomic reserve in watermark fast page_alloc: fix invalid watermark check on a negative value
Joonsoo Kim (1): mm/page_alloc: use ac->high_zoneidx for classzone_idx
mm/internal.h | 2 +- mm/page_alloc.c | 69 +++++++++++++++++++++++++++++++++------------------------ 2 files changed, 41 insertions(+), 30 deletions(-)
From: Joonsoo Kim iamjoonsoo.kim@lge.com
Patch series "integrate classzone_idx and high_zoneidx", v5.
This patchset is followup of the problem reported and discussed two years ago [1, 2]. The problem this patchset solves is related to the classzone_idx on the NUMA system. It causes a problem when the lowmem reserve protection exists for some zones on a node that do not exist on other nodes.
This problem was reported two years ago, and, at that time, the solution got general agreements [2]. But it was not upstreamed.
[1]: http://lkml.kernel.org/r/20180102063528.GG30397@yexl-desktop [2]: http://lkml.kernel.org/r/1525408246-14768-1-git-send-email-iamjoonsoo.kim@lg...
This patch (of 2):
Currently, we use classzone_idx to calculate lowmem reserve proetection for an allocation request. This classzone_idx causes a problem on NUMA systems when the lowmem reserve protection exists for some zones on a node that do not exist on other nodes.
Before further explanation, I should first clarify how to compute the classzone_idx and the high_zoneidx.
- ac->high_zoneidx is computed via the arcane gfp_zone(gfp_mask) and represents the index of the highest zone the allocation can use
- classzone_idx was supposed to be the index of the highest zone on the local node that the allocation can use, that is actually available in the system
Think about following example. Node 0 has 4 populated zone, DMA/DMA32/NORMAL/MOVABLE. Node 1 has 1 populated zone, NORMAL. Some zones, such as MOVABLE, doesn't exist on node 1 and this makes following difference.
Assume that there is an allocation request whose gfp_zone(gfp_mask) is the zone, MOVABLE. Then, it's high_zoneidx is 3. If this allocation is initiated on node 0, it's classzone_idx is 3 since actually available/usable zone on local (node 0) is MOVABLE. If this allocation is initiated on node 1, it's classzone_idx is 2 since actually available/usable zone on local (node 1) is NORMAL.
You can see that classzone_idx of the allocation request are different according to their starting node, even if their high_zoneidx is the same.
Think more about these two allocation requests. If they are processed on local, there is no problem. However, if allocation is initiated on node 1 are processed on remote, in this example, at the NORMAL zone on node 0, due to memory shortage, problem occurs. Their different classzone_idx leads to different lowmem reserve and then different min watermark. See the following example.
root@ubuntu:/sys/devices/system/memory# cat /proc/zoneinfo Node 0, zone DMA per-node stats ... pages free 3965 min 5 low 8 high 11 spanned 4095 present 3998 managed 3977 protection: (0, 2961, 4928, 5440) ... Node 0, zone DMA32 pages free 757955 min 1129 low 1887 high 2645 spanned 1044480 present 782303 managed 758116 protection: (0, 0, 1967, 2479) ... Node 0, zone Normal pages free 459806 min 750 low 1253 high 1756 spanned 524288 present 524288 managed 503620 protection: (0, 0, 0, 4096) ... Node 0, zone Movable pages free 130759 min 195 low 326 high 457 spanned 1966079 present 131072 managed 131072 protection: (0, 0, 0, 0) ... Node 1, zone DMA pages free 0 min 0 low 0 high 0 spanned 0 present 0 managed 0 protection: (0, 0, 1006, 1006) Node 1, zone DMA32 pages free 0 min 0 low 0 high 0 spanned 0 present 0 managed 0 protection: (0, 0, 1006, 1006) Node 1, zone Normal per-node stats ... pages free 233277 min 383 low 640 high 897 spanned 262144 present 262144 managed 257744 protection: (0, 0, 0, 0) ... Node 1, zone Movable pages free 0 min 0 low 0 high 0 spanned 262144 present 0 managed 0 protection: (0, 0, 0, 0)
- static min watermark for the NORMAL zone on node 0 is 750.
- lowmem reserve for the request with classzone idx 3 at the NORMAL on node 0 is 4096.
- lowmem reserve for the request with classzone idx 2 at the NORMAL on node 0 is 0.
So, overall min watermark is: allocation initiated on node 0 (classzone_idx 3): 750 + 4096 = 4846 allocation initiated on node 1 (classzone_idx 2): 750 + 0 = 750
Allocation initiated on node 1 will have some precedence than allocation initiated on node 0 because min watermark of the former allocation is lower than the other. So, allocation initiated on node 1 could succeed on node 0 when allocation initiated on node 0 could not, and, this could cause too many numa_miss allocation. Then, performance could be downgraded.
Recently, there was a regression report about this problem on CMA patches since CMA memory are placed in ZONE_MOVABLE by those patches. I checked that problem is disappeared with this fix that uses high_zoneidx for classzone_idx.
http://lkml.kernel.org/r/20180102063528.GG30397@yexl-desktop
Using high_zoneidx for classzone_idx is more consistent way than previous approach because system's memory layout doesn't affect anything to it. With this patch, both classzone_idx on above example will be 3 so will have the same min watermark.
allocation initiated on node 0: 750 + 4096 = 4846 allocation initiated on node 1: 750 + 4096 = 4846
One could wonder if there is a side effect that allocation initiated on node 1 will use higher bar when allocation is handled on local since classzone_idx could be higher than before. It will not happen because the zone without managed page doesn't contributes lowmem_reserve at all.
Reported-by: Ye Xiaolong xiaolong.ye@intel.com Signed-off-by: Joonsoo Kim iamjoonsoo.kim@lge.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Tested-by: Ye Xiaolong xiaolong.ye@intel.com Reviewed-by: Baoquan He bhe@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Acked-by: David Rientjes rientjes@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Minchan Kim minchan@kernel.org Cc: Mel Gorman mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1587095923-7515-1-git-send-email-iamjoonsoo.kim@lge... Link: http://lkml.kernel.org/r/1587095923-7515-2-git-send-email-iamjoonsoo.kim@lge... Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- mm/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/internal.h b/mm/internal.h index 3a2e973..922a173 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -123,7 +123,7 @@ struct alloc_context { bool spread_dirty_pages; };
-#define ac_classzone_idx(ac) zonelist_zone_idx(ac->preferred_zoneref) +#define ac_classzone_idx(ac) (ac->high_zoneidx)
/* * Locate the struct page for both the matching buddy in our
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
Rule: 'Cc: stable@vger.kernel.org' or 'commit <sha1> upstream.' Subject: [PATCH 1/3] mm/page_alloc: use ac->high_zoneidx for classzone_idx Link: https://lore.kernel.org/stable/1663347949-20389-2-git-send-email-wang.yong12...
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
From: Jaewon Kim jaewon31.kim@samsung.com
zone_watermark_fast was introduced by commit 48ee5f3696f6 ("mm, page_alloc: shortcut watermark checks for order-0 pages"). The commit simply checks if free pages is bigger than watermark without additional calculation such like reducing watermark.
It considered free cma pages but it did not consider highatomic reserved. This may incur exhaustion of free pages except high order atomic free pages.
Assume that reserved_highatomic pageblock is bigger than watermark min, and there are only few free pages except high order atomic free. Because zone_watermark_fast passes the allocation without considering high order atomic free, normal reclaimable allocation like GFP_HIGHUSER will consume all the free pages. Then finally order-0 atomic allocation may fail on allocation.
This means watermark min is not protected against non-atomic allocation. The order-0 atomic allocation with ALLOC_HARDER unwantedly can be failed. Additionally the __GFP_MEMALLOC allocation with ALLOC_NO_WATERMARKS also can be failed.
To avoid the problem, zone_watermark_fast should consider highatomic reserve. If the actual size of high atomic free is counted accurately like cma free, we may use it. On this patch just use nr_reserved_highatomic. Additionally introduce __zone_watermark_unusable_free to factor out common parts between zone_watermark_fast and __zone_watermark_ok.
This is an example of ALLOC_HARDER allocation failure using v4.19 based kernel.
Binder:9343_3: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null) Call trace: [<ffffff8008f40f8c>] dump_stack+0xb8/0xf0 [<ffffff8008223320>] warn_alloc+0xd8/0x12c [<ffffff80082245e4>] __alloc_pages_nodemask+0x120c/0x1250 [<ffffff800827f6e8>] new_slab+0x128/0x604 [<ffffff800827b0cc>] ___slab_alloc+0x508/0x670 [<ffffff800827ba00>] __kmalloc+0x2f8/0x310 [<ffffff80084ac3e0>] context_struct_to_string+0x104/0x1cc [<ffffff80084ad8fc>] security_sid_to_context_core+0x74/0x144 [<ffffff80084ad880>] security_sid_to_context+0x10/0x18 [<ffffff800849bd80>] selinux_secid_to_secctx+0x20/0x28 [<ffffff800849109c>] security_secid_to_secctx+0x3c/0x70 [<ffffff8008bfe118>] binder_transaction+0xe68/0x454c Mem-Info: active_anon:102061 inactive_anon:81551 isolated_anon:0 active_file:59102 inactive_file:68924 isolated_file:64 unevictable:611 dirty:63 writeback:0 unstable:0 slab_reclaimable:13324 slab_unreclaimable:44354 mapped:83015 shmem:4858 pagetables:26316 bounce:0 free:2727 free_pcp:1035 free_cma:178 Node 0 active_anon:408244kB inactive_anon:326204kB active_file:236408kB inactive_file:275696kB unevictable:2444kB isolated(anon):0kB isolated(file):256kB mapped:332060kB dirty:252kB writeback:0kB shmem:19432kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no Normal free:10908kB min:6192kB low:44388kB high:47060kB active_anon:409160kB inactive_anon:325924kB active_file:235820kB inactive_file:276628kB unevictable:2444kB writepending:252kB present:3076096kB managed:2673676kB mlocked:2444kB kernel_stack:62512kB pagetables:105264kB bounce:0kB free_pcp:4140kB local_pcp:40kB free_cma:712kB lowmem_reserve[]: 0 0 Normal: 505*4kB (H) 357*8kB (H) 201*16kB (H) 65*32kB (H) 1*64kB (H) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 10236kB 138826 total pagecache pages 5460 pages in swap cache Swap cache stats: add 8273090, delete 8267506, find 1004381/4060142
This is an example of ALLOC_NO_WATERMARKS allocation failure using v4.14 based kernel.
kswapd0: page allocation failure: order:0, mode:0x140000a(GFP_NOIO|__GFP_HIGHMEM|__GFP_MOVABLE), nodemask=(null) kswapd0 cpuset=/ mems_allowed=0 CPU: 4 PID: 1221 Comm: kswapd0 Not tainted 4.14.113-18770262-userdebug #1 Call trace: [<0000000000000000>] dump_backtrace+0x0/0x248 [<0000000000000000>] show_stack+0x18/0x20 [<0000000000000000>] __dump_stack+0x20/0x28 [<0000000000000000>] dump_stack+0x68/0x90 [<0000000000000000>] warn_alloc+0x104/0x198 [<0000000000000000>] __alloc_pages_nodemask+0xdc0/0xdf0 [<0000000000000000>] zs_malloc+0x148/0x3d0 [<0000000000000000>] zram_bvec_rw+0x410/0x798 [<0000000000000000>] zram_rw_page+0x88/0xdc [<0000000000000000>] bdev_write_page+0x70/0xbc [<0000000000000000>] __swap_writepage+0x58/0x37c [<0000000000000000>] swap_writepage+0x40/0x4c [<0000000000000000>] shrink_page_list+0xc30/0xf48 [<0000000000000000>] shrink_inactive_list+0x2b0/0x61c [<0000000000000000>] shrink_node_memcg+0x23c/0x618 [<0000000000000000>] shrink_node+0x1c8/0x304 [<0000000000000000>] kswapd+0x680/0x7c4 [<0000000000000000>] kthread+0x110/0x120 [<0000000000000000>] ret_from_fork+0x10/0x18 Mem-Info: active_anon:111826 inactive_anon:65557 isolated_anon:0\x0a active_file:44260 inactive_file:83422 isolated_file:0\x0a unevictable:4158 dirty:117 writeback:0 unstable:0\x0a slab_reclaimable:13943 slab_unreclaimable:43315\x0a mapped:102511 shmem:3299 pagetables:19566 bounce:0\x0a free:3510 free_pcp:553 free_cma:0 Node 0 active_anon:447304kB inactive_anon:262228kB active_file:177040kB inactive_file:333688kB unevictable:16632kB isolated(anon):0kB isolated(file):0kB mapped:410044kB d irty:468kB writeback:0kB shmem:13196kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no Normal free:14040kB min:7440kB low:94500kB high:98136kB reserved_highatomic:32768KB active_anon:447336kB inactive_anon:261668kB active_file:177572kB inactive_file:333768k B unevictable:16632kB writepending:480kB present:4081664kB managed:3637088kB mlocked:16632kB kernel_stack:47072kB pagetables:78264kB bounce:0kB free_pcp:2280kB local_pcp:720kB free_cma:0kB [ 4738.329607] lowmem_reserve[]: 0 0 Normal: 860*4kB (H) 453*8kB (H) 180*16kB (H) 26*32kB (H) 34*64kB (H) 6*128kB (H) 2*256kB (H) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 14232kB
This is trace log which shows GFP_HIGHUSER consumes free pages right before ALLOC_NO_WATERMARKS.
<...>-22275 [006] .... 889.213383: mm_page_alloc: page=00000000d2be5665 pfn=970744 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213385: mm_page_alloc: page=000000004b2335c2 pfn=970745 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213387: mm_page_alloc: page=00000000017272e1 pfn=970278 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213389: mm_page_alloc: page=00000000c4be79fb pfn=970279 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213391: mm_page_alloc: page=00000000f8a51d4f pfn=970260 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213393: mm_page_alloc: page=000000006ba8f5ac pfn=970261 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213395: mm_page_alloc: page=00000000819f1cd3 pfn=970196 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213396: mm_page_alloc: page=00000000f6b72a64 pfn=970197 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO kswapd0-1207 [005] ...1 889.213398: mm_page_alloc: page= (null) pfn=0 order=0 migratetype=1 nr_free=3650 gfp_flags=GFP_NOWAIT|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_MOVABLE
[jaewon31.kim@samsung.com: remove redundant code for high-order] Link: http://lkml.kernel.org/r/20200623035242.27232-1-jaewon31.kim@samsung.com
Reported-by: Yong-Taek Lee ytk.lee@samsung.com Suggested-by: Minchan Kim minchan@kernel.org Signed-off-by: Jaewon Kim jaewon31.kim@samsung.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Baoquan He bhe@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Johannes Weiner hannes@cmpxchg.org Cc: Yong-Taek Lee ytk.lee@samsung.com Cc: Michal Hocko mhocko@kernel.org Link: http://lkml.kernel.org/r/20200619235958.11283-1-jaewon31.kim@samsung.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- mm/page_alloc.c | 65 ++++++++++++++++++++++++++++++++------------------------- 1 file changed, 36 insertions(+), 29 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9c35403..237463d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3130,6 +3130,29 @@ static inline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
#endif /* CONFIG_FAIL_PAGE_ALLOC */
+static inline long __zone_watermark_unusable_free(struct zone *z, + unsigned int order, unsigned int alloc_flags) +{ + const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); + long unusable_free = (1 << order) - 1; + + /* + * If the caller does not have rights to ALLOC_HARDER then subtract + * the high-atomic reserves. This will over-estimate the size of the + * atomic reserve but it avoids a search. + */ + if (likely(!alloc_harder)) + unusable_free += z->nr_reserved_highatomic; + +#ifdef CONFIG_CMA + /* If allocation can't use CMA areas don't use free CMA pages */ + if (!(alloc_flags & ALLOC_CMA)) + unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES); +#endif + + return unusable_free; +} + /* * Return true if free base pages are above 'mark'. For high-order checks it * will return true of the order-0 watermark is reached and there is at least @@ -3145,19 +3168,12 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
/* free_pages may go negative - that's OK */ - free_pages -= (1 << order) - 1; + free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
if (alloc_flags & ALLOC_HIGH) min -= min / 2;
- /* - * If the caller does not have rights to ALLOC_HARDER then subtract - * the high-atomic reserves. This will over-estimate the size of the - * atomic reserve but it avoids a search. - */ - if (likely(!alloc_harder)) { - free_pages -= z->nr_reserved_highatomic; - } else { + if (unlikely(alloc_harder)) { /* * OOM victims can try even harder than normal ALLOC_HARDER * users on the grounds that it's definitely going to be in @@ -3170,13 +3186,6 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, min -= min / 4; }
- -#ifdef CONFIG_CMA - /* If allocation can't use CMA areas don't use free CMA pages */ - if (!(alloc_flags & ALLOC_CMA)) - free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES); -#endif - /* * Check watermarks for an order-0 allocation request. If these * are not met, then a high-order request also cannot go ahead @@ -3225,24 +3234,22 @@ bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, static inline bool zone_watermark_fast(struct zone *z, unsigned int order, unsigned long mark, int classzone_idx, unsigned int alloc_flags) { - long free_pages = zone_page_state(z, NR_FREE_PAGES); - long cma_pages = 0; + long free_pages;
-#ifdef CONFIG_CMA - /* If allocation can't use CMA areas don't use free CMA pages */ - if (!(alloc_flags & ALLOC_CMA)) - cma_pages = zone_page_state(z, NR_FREE_CMA_PAGES); -#endif + free_pages = zone_page_state(z, NR_FREE_PAGES);
/* * Fast check for order-0 only. If this fails then the reserves - * need to be calculated. There is a corner case where the check - * passes but only the high-order atomic reserve are free. If - * the caller is !atomic then it'll uselessly search the free - * list. That corner case is then slower but it is harmless. + * need to be calculated. */ - if (!order && (free_pages - cma_pages) > mark + z->lowmem_reserve[classzone_idx]) - return true; + if (!order) { + long fast_free; + + fast_free = free_pages; + fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags); + if (fast_free > mark + z->lowmem_reserve[classzone_idx]) + return true; + }
return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, free_pages);
From: Jaewon Kim jaewon31.kim@samsung.com
There was a report that a task is waiting at the throttle_direct_reclaim. The pgscan_direct_throttle in vmstat was increasing.
This is a bug where zone_watermark_fast returns true even when the free is very low. The commit f27ce0e14088 ("page_alloc: consider highatomic reserve in watermark fast") changed the watermark fast to consider highatomic reserve. But it did not handle a negative value case which can be happened when reserved_highatomic pageblock is bigger than the actual free.
If watermark is considered as ok for the negative value, allocating contexts for order-0 will consume all free pages without direct reclaim, and finally free page may become depleted except highatomic free.
Then allocating contexts may fall into throttle_direct_reclaim. This symptom may easily happen in a system where wmark min is low and other reclaimers like kswapd does not make free pages quickly.
Handle the negative case by using MIN.
Link: https://lkml.kernel.org/r/20220725095212.25388-1-jaewon31.kim@samsung.com Fixes: f27ce0e14088 ("page_alloc: consider highatomic reserve in watermark fast") Signed-off-by: Jaewon Kim jaewon31.kim@samsung.com Reported-by: GyeongHwan Hong gh21.hong@samsung.com Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Minchan Kim minchan@kernel.org Cc: Baoquan He bhe@redhat.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Yong-Taek Lee ytk.lee@samsung.com Cc: stable@vger.kerenl.org Signed-off-by: Andrew Morton akpm@linux-foundation.org --- mm/page_alloc.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 237463d..d6d8a37 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3243,11 +3243,15 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, * need to be calculated. */ if (!order) { - long fast_free; + long usable_free; + long reserved;
- fast_free = free_pages; - fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags); - if (fast_free > mark + z->lowmem_reserve[classzone_idx]) + usable_free = free_pages; + reserved = __zone_watermark_unusable_free(z, 0, alloc_flags); + + /* reserved may over estimate high-atomic reserves. */ + usable_free -= min(usable_free, reserved); + if (usable_free > mark + z->lowmem_reserve[classzone_idx]) return true; }
On Fri, Sep 16, 2022 at 10:05:46AM -0700, wangyong wrote:
Here are the corresponding backports to 4.19. And fix classzone_idx context differences causing patch merge conflicts.
Jaewon Kim (2): page_alloc: consider highatomic reserve in watermark fast page_alloc: fix invalid watermark check on a negative value
Joonsoo Kim (1): mm/page_alloc: use ac->high_zoneidx for classzone_idx
mm/internal.h | 2 +- mm/page_alloc.c | 69 +++++++++++++++++++++++++++++++++------------------------ 2 files changed, 41 insertions(+), 30 deletions(-)
-- 2.7.4
What are the git commit ids of these commits? That needs to be in the commit changelog.
Also you did not sign off on the backports, please fix that up when you resend this series.
thanks,
greg k-h
Here are the corresponding backports to 4.19. And fix classzone_idx context differences causing patch merge conflicts.
Original commit IDS: 3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx f27ce0e page_alloc: consider highatomic reserve in watermark fast 9282012 page_alloc: fix invalid watermark check on a negative value
Changes from v1: - Add commit information of the original patches.
Jaewon Kim (2): page_alloc: consider highatomic reserve in watermark fast page_alloc: fix invalid watermark check on a negative value
Joonsoo Kim (1): mm/page_alloc: use ac->high_zoneidx for classzone_idx
mm/internal.h | 2 +- mm/page_alloc.c | 69 +++++++++++++++++++++++++++++++++------------------------ 2 files changed, 41 insertions(+), 30 deletions(-)
From: Joonsoo Kim iamjoonsoo.kim@lge.com
[ backport of commit 3334a45eb9e2bb040c880ef65e1d72357a0a008b ]
Patch series "integrate classzone_idx and high_zoneidx", v5.
This patchset is followup of the problem reported and discussed two years ago [1, 2]. The problem this patchset solves is related to the classzone_idx on the NUMA system. It causes a problem when the lowmem reserve protection exists for some zones on a node that do not exist on other nodes.
This problem was reported two years ago, and, at that time, the solution got general agreements [2]. But it was not upstreamed.
[1]: http://lkml.kernel.org/r/20180102063528.GG30397@yexl-desktop [2]: http://lkml.kernel.org/r/1525408246-14768-1-git-send-email-iamjoonsoo.kim@lg...
This patch (of 2):
Currently, we use classzone_idx to calculate lowmem reserve proetection for an allocation request. This classzone_idx causes a problem on NUMA systems when the lowmem reserve protection exists for some zones on a node that do not exist on other nodes.
Before further explanation, I should first clarify how to compute the classzone_idx and the high_zoneidx.
- ac->high_zoneidx is computed via the arcane gfp_zone(gfp_mask) and represents the index of the highest zone the allocation can use
- classzone_idx was supposed to be the index of the highest zone on the local node that the allocation can use, that is actually available in the system
Think about following example. Node 0 has 4 populated zone, DMA/DMA32/NORMAL/MOVABLE. Node 1 has 1 populated zone, NORMAL. Some zones, such as MOVABLE, doesn't exist on node 1 and this makes following difference.
Assume that there is an allocation request whose gfp_zone(gfp_mask) is the zone, MOVABLE. Then, it's high_zoneidx is 3. If this allocation is initiated on node 0, it's classzone_idx is 3 since actually available/usable zone on local (node 0) is MOVABLE. If this allocation is initiated on node 1, it's classzone_idx is 2 since actually available/usable zone on local (node 1) is NORMAL.
You can see that classzone_idx of the allocation request are different according to their starting node, even if their high_zoneidx is the same.
Think more about these two allocation requests. If they are processed on local, there is no problem. However, if allocation is initiated on node 1 are processed on remote, in this example, at the NORMAL zone on node 0, due to memory shortage, problem occurs. Their different classzone_idx leads to different lowmem reserve and then different min watermark. See the following example.
root@ubuntu:/sys/devices/system/memory# cat /proc/zoneinfo Node 0, zone DMA per-node stats ... pages free 3965 min 5 low 8 high 11 spanned 4095 present 3998 managed 3977 protection: (0, 2961, 4928, 5440) ... Node 0, zone DMA32 pages free 757955 min 1129 low 1887 high 2645 spanned 1044480 present 782303 managed 758116 protection: (0, 0, 1967, 2479) ... Node 0, zone Normal pages free 459806 min 750 low 1253 high 1756 spanned 524288 present 524288 managed 503620 protection: (0, 0, 0, 4096) ... Node 0, zone Movable pages free 130759 min 195 low 326 high 457 spanned 1966079 present 131072 managed 131072 protection: (0, 0, 0, 0) ... Node 1, zone DMA pages free 0 min 0 low 0 high 0 spanned 0 present 0 managed 0 protection: (0, 0, 1006, 1006) Node 1, zone DMA32 pages free 0 min 0 low 0 high 0 spanned 0 present 0 managed 0 protection: (0, 0, 1006, 1006) Node 1, zone Normal per-node stats ... pages free 233277 min 383 low 640 high 897 spanned 262144 present 262144 managed 257744 protection: (0, 0, 0, 0) ... Node 1, zone Movable pages free 0 min 0 low 0 high 0 spanned 262144 present 0 managed 0 protection: (0, 0, 0, 0)
- static min watermark for the NORMAL zone on node 0 is 750.
- lowmem reserve for the request with classzone idx 3 at the NORMAL on node 0 is 4096.
- lowmem reserve for the request with classzone idx 2 at the NORMAL on node 0 is 0.
So, overall min watermark is: allocation initiated on node 0 (classzone_idx 3): 750 + 4096 = 4846 allocation initiated on node 1 (classzone_idx 2): 750 + 0 = 750
Allocation initiated on node 1 will have some precedence than allocation initiated on node 0 because min watermark of the former allocation is lower than the other. So, allocation initiated on node 1 could succeed on node 0 when allocation initiated on node 0 could not, and, this could cause too many numa_miss allocation. Then, performance could be downgraded.
Recently, there was a regression report about this problem on CMA patches since CMA memory are placed in ZONE_MOVABLE by those patches. I checked that problem is disappeared with this fix that uses high_zoneidx for classzone_idx.
http://lkml.kernel.org/r/20180102063528.GG30397@yexl-desktop
Using high_zoneidx for classzone_idx is more consistent way than previous approach because system's memory layout doesn't affect anything to it. With this patch, both classzone_idx on above example will be 3 so will have the same min watermark.
allocation initiated on node 0: 750 + 4096 = 4846 allocation initiated on node 1: 750 + 4096 = 4846
One could wonder if there is a side effect that allocation initiated on node 1 will use higher bar when allocation is handled on local since classzone_idx could be higher than before. It will not happen because the zone without managed page doesn't contributes lowmem_reserve at all.
Reported-by: Ye Xiaolong xiaolong.ye@intel.com Signed-off-by: Joonsoo Kim iamjoonsoo.kim@lge.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Tested-by: Ye Xiaolong xiaolong.ye@intel.com Reviewed-by: Baoquan He bhe@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Acked-by: David Rientjes rientjes@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Minchan Kim minchan@kernel.org Cc: Mel Gorman mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1587095923-7515-1-git-send-email-iamjoonsoo.kim@lge... Link: http://lkml.kernel.org/r/1587095923-7515-2-git-send-email-iamjoonsoo.kim@lge... Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- mm/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/internal.h b/mm/internal.h index 3a2e973..922a173 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -123,7 +123,7 @@ struct alloc_context { bool spread_dirty_pages; };
-#define ac_classzone_idx(ac) zonelist_zone_idx(ac->preferred_zoneref) +#define ac_classzone_idx(ac) (ac->high_zoneidx)
/* * Locate the struct page for both the matching buddy in our
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
Rule: 'Cc: stable@vger.kernel.org' or 'commit <sha1> upstream.' Subject: [PATCH v2 stable-4.19 1/3] mm/page_alloc: use ac->high_zoneidx for classzone_idx Link: https://lore.kernel.org/stable/20220925103529.13716-2-yongw.pur%40gmail.com
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
On Sun, Sep 25, 2022 at 03:35:27AM -0700, wangyong wrote:
From: Joonsoo Kim iamjoonsoo.kim@lge.com
[ backport of commit 3334a45eb9e2bb040c880ef65e1d72357a0a008b ]
This is from 5.8. What about the 5.4.y kernel? Why would someone upgrading from 4.19.y to 5.4.y suffer a regression here?
And why wouldn't someone who has this issue just not use 5.10.y instead? What prevents someone from moving off of 4.19.y at this point in time?
thanks,
greg k-h
Greg KH gregkh@linuxfoundation.org 于2022年9月25日周日 19:00写道：
On Sun, Sep 25, 2022 at 03:35:27AM -0700, wangyong wrote:
From: Joonsoo Kim iamjoonsoo.kim@lge.com
[ backport of commit 3334a45eb9e2bb040c880ef65e1d72357a0a008b ]
This is from 5.8. What about the 5.4.y kernel? Why would someone upgrading from 4.19.y to 5.4.y suffer a regression here?
I encountered this problem on 4.19, but I haven't encountered it on 5.4. However, this should be a common problem, so 5.4 may also need to be merged.
Hello, Joonsoo, what do you think?
And why wouldn't someone who has this issue just not use 5.10.y instead? What prevents someone from moving off of 4.19.y at this point in time?
This is a solution, but upgrading the kernel version requires time and overhead, so use the patch is the most effective way, if there is.
Thanks.
thanks,
greg k-h
On Sun, Sep 25, 2022 at 10:32:32PM +0800, yong w wrote:
Greg KH gregkh@linuxfoundation.org 于2022年9月25日周日 19:00写道：
On Sun, Sep 25, 2022 at 03:35:27AM -0700, wangyong wrote:
From: Joonsoo Kim iamjoonsoo.kim@lge.com
[ backport of commit 3334a45eb9e2bb040c880ef65e1d72357a0a008b ]
This is from 5.8. What about the 5.4.y kernel? Why would someone upgrading from 4.19.y to 5.4.y suffer a regression here?
I encountered this problem on 4.19, but I haven't encountered it on 5.4. However, this should be a common problem, so 5.4 may also need to be merged.
Hello, Joonsoo, what do you think?
And why wouldn't someone who has this issue just not use 5.10.y instead? What prevents someone from moving off of 4.19.y at this point in time?
This is a solution, but upgrading the kernel version requires time and overhead, so use the patch is the most effective way, if there is.
You will have to move off of 4.19 soon anyway, so why delay the change?
thanks,
greg k-h
From: Jaewon Kim jaewon31.kim@samsung.com
[ backport of commit f27ce0e14088b23f8d54ae4a44f70307ec420e64 ]
zone_watermark_fast was introduced by commit 48ee5f3696f6 ("mm, page_alloc: shortcut watermark checks for order-0 pages"). The commit simply checks if free pages is bigger than watermark without additional calculation such like reducing watermark.
It considered free cma pages but it did not consider highatomic reserved. This may incur exhaustion of free pages except high order atomic free pages.
Assume that reserved_highatomic pageblock is bigger than watermark min, and there are only few free pages except high order atomic free. Because zone_watermark_fast passes the allocation without considering high order atomic free, normal reclaimable allocation like GFP_HIGHUSER will consume all the free pages. Then finally order-0 atomic allocation may fail on allocation.
This means watermark min is not protected against non-atomic allocation. The order-0 atomic allocation with ALLOC_HARDER unwantedly can be failed. Additionally the __GFP_MEMALLOC allocation with ALLOC_NO_WATERMARKS also can be failed.
To avoid the problem, zone_watermark_fast should consider highatomic reserve. If the actual size of high atomic free is counted accurately like cma free, we may use it. On this patch just use nr_reserved_highatomic. Additionally introduce __zone_watermark_unusable_free to factor out common parts between zone_watermark_fast and __zone_watermark_ok.
This is an example of ALLOC_HARDER allocation failure using v4.19 based kernel.
Binder:9343_3: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null) Call trace: [<ffffff8008f40f8c>] dump_stack+0xb8/0xf0 [<ffffff8008223320>] warn_alloc+0xd8/0x12c [<ffffff80082245e4>] __alloc_pages_nodemask+0x120c/0x1250 [<ffffff800827f6e8>] new_slab+0x128/0x604 [<ffffff800827b0cc>] ___slab_alloc+0x508/0x670 [<ffffff800827ba00>] __kmalloc+0x2f8/0x310 [<ffffff80084ac3e0>] context_struct_to_string+0x104/0x1cc [<ffffff80084ad8fc>] security_sid_to_context_core+0x74/0x144 [<ffffff80084ad880>] security_sid_to_context+0x10/0x18 [<ffffff800849bd80>] selinux_secid_to_secctx+0x20/0x28 [<ffffff800849109c>] security_secid_to_secctx+0x3c/0x70 [<ffffff8008bfe118>] binder_transaction+0xe68/0x454c Mem-Info: active_anon:102061 inactive_anon:81551 isolated_anon:0 active_file:59102 inactive_file:68924 isolated_file:64 unevictable:611 dirty:63 writeback:0 unstable:0 slab_reclaimable:13324 slab_unreclaimable:44354 mapped:83015 shmem:4858 pagetables:26316 bounce:0 free:2727 free_pcp:1035 free_cma:178 Node 0 active_anon:408244kB inactive_anon:326204kB active_file:236408kB inactive_file:275696kB unevictable:2444kB isolated(anon):0kB isolated(file):256kB mapped:332060kB dirty:252kB writeback:0kB shmem:19432kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no Normal free:10908kB min:6192kB low:44388kB high:47060kB active_anon:409160kB inactive_anon:325924kB active_file:235820kB inactive_file:276628kB unevictable:2444kB writepending:252kB present:3076096kB managed:2673676kB mlocked:2444kB kernel_stack:62512kB pagetables:105264kB bounce:0kB free_pcp:4140kB local_pcp:40kB free_cma:712kB lowmem_reserve[]: 0 0 Normal: 505*4kB (H) 357*8kB (H) 201*16kB (H) 65*32kB (H) 1*64kB (H) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 10236kB 138826 total pagecache pages 5460 pages in swap cache Swap cache stats: add 8273090, delete 8267506, find 1004381/4060142
This is an example of ALLOC_NO_WATERMARKS allocation failure using v4.14 based kernel.
kswapd0: page allocation failure: order:0, mode:0x140000a(GFP_NOIO|__GFP_HIGHMEM|__GFP_MOVABLE), nodemask=(null) kswapd0 cpuset=/ mems_allowed=0 CPU: 4 PID: 1221 Comm: kswapd0 Not tainted 4.14.113-18770262-userdebug #1 Call trace: [<0000000000000000>] dump_backtrace+0x0/0x248 [<0000000000000000>] show_stack+0x18/0x20 [<0000000000000000>] __dump_stack+0x20/0x28 [<0000000000000000>] dump_stack+0x68/0x90 [<0000000000000000>] warn_alloc+0x104/0x198 [<0000000000000000>] __alloc_pages_nodemask+0xdc0/0xdf0 [<0000000000000000>] zs_malloc+0x148/0x3d0 [<0000000000000000>] zram_bvec_rw+0x410/0x798 [<0000000000000000>] zram_rw_page+0x88/0xdc [<0000000000000000>] bdev_write_page+0x70/0xbc [<0000000000000000>] __swap_writepage+0x58/0x37c [<0000000000000000>] swap_writepage+0x40/0x4c [<0000000000000000>] shrink_page_list+0xc30/0xf48 [<0000000000000000>] shrink_inactive_list+0x2b0/0x61c [<0000000000000000>] shrink_node_memcg+0x23c/0x618 [<0000000000000000>] shrink_node+0x1c8/0x304 [<0000000000000000>] kswapd+0x680/0x7c4 [<0000000000000000>] kthread+0x110/0x120 [<0000000000000000>] ret_from_fork+0x10/0x18 Mem-Info: active_anon:111826 inactive_anon:65557 isolated_anon:0\x0a active_file:44260 inactive_file:83422 isolated_file:0\x0a unevictable:4158 dirty:117 writeback:0 unstable:0\x0a slab_reclaimable:13943 slab_unreclaimable:43315\x0a mapped:102511 shmem:3299 pagetables:19566 bounce:0\x0a free:3510 free_pcp:553 free_cma:0 Node 0 active_anon:447304kB inactive_anon:262228kB active_file:177040kB inactive_file:333688kB unevictable:16632kB isolated(anon):0kB isolated(file):0kB mapped:410044kB d irty:468kB writeback:0kB shmem:13196kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no Normal free:14040kB min:7440kB low:94500kB high:98136kB reserved_highatomic:32768KB active_anon:447336kB inactive_anon:261668kB active_file:177572kB inactive_file:333768k B unevictable:16632kB writepending:480kB present:4081664kB managed:3637088kB mlocked:16632kB kernel_stack:47072kB pagetables:78264kB bounce:0kB free_pcp:2280kB local_pcp:720kB free_cma:0kB [ 4738.329607] lowmem_reserve[]: 0 0 Normal: 860*4kB (H) 453*8kB (H) 180*16kB (H) 26*32kB (H) 34*64kB (H) 6*128kB (H) 2*256kB (H) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 14232kB
This is trace log which shows GFP_HIGHUSER consumes free pages right before ALLOC_NO_WATERMARKS.
<...>-22275 [006] .... 889.213383: mm_page_alloc: page=00000000d2be5665 pfn=970744 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213385: mm_page_alloc: page=000000004b2335c2 pfn=970745 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213387: mm_page_alloc: page=00000000017272e1 pfn=970278 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213389: mm_page_alloc: page=00000000c4be79fb pfn=970279 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213391: mm_page_alloc: page=00000000f8a51d4f pfn=970260 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213393: mm_page_alloc: page=000000006ba8f5ac pfn=970261 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213395: mm_page_alloc: page=00000000819f1cd3 pfn=970196 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO <...>-22275 [006] .... 889.213396: mm_page_alloc: page=00000000f6b72a64 pfn=970197 order=0 migratetype=0 nr_free=3650 gfp_flags=GFP_HIGHUSER|__GFP_ZERO kswapd0-1207 [005] ...1 889.213398: mm_page_alloc: page= (null) pfn=0 order=0 migratetype=1 nr_free=3650 gfp_flags=GFP_NOWAIT|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_MOVABLE
[jaewon31.kim@samsung.com: remove redundant code for high-order] Link: http://lkml.kernel.org/r/20200623035242.27232-1-jaewon31.kim@samsung.com
Reported-by: Yong-Taek Lee ytk.lee@samsung.com Suggested-by: Minchan Kim minchan@kernel.org Signed-off-by: Jaewon Kim jaewon31.kim@samsung.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Baoquan He bhe@redhat.com Acked-by: Vlastimil Babka vbabka@suse.cz Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Johannes Weiner hannes@cmpxchg.org Cc: Yong-Taek Lee ytk.lee@samsung.com Cc: Michal Hocko mhocko@kernel.org Link: http://lkml.kernel.org/r/20200619235958.11283-1-jaewon31.kim@samsung.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- mm/page_alloc.c | 65 ++++++++++++++++++++++++++++++++------------------------- 1 file changed, 36 insertions(+), 29 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 9c35403..237463d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3130,6 +3130,29 @@ static inline bool should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
#endif /* CONFIG_FAIL_PAGE_ALLOC */
+static inline long __zone_watermark_unusable_free(struct zone *z, + unsigned int order, unsigned int alloc_flags) +{ + const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM)); + long unusable_free = (1 << order) - 1; + + /* + * If the caller does not have rights to ALLOC_HARDER then subtract + * the high-atomic reserves. This will over-estimate the size of the + * atomic reserve but it avoids a search. + */ + if (likely(!alloc_harder)) + unusable_free += z->nr_reserved_highatomic; + +#ifdef CONFIG_CMA + /* If allocation can't use CMA areas don't use free CMA pages */ + if (!(alloc_flags & ALLOC_CMA)) + unusable_free += zone_page_state(z, NR_FREE_CMA_PAGES); +#endif + + return unusable_free; +} + /* * Return true if free base pages are above 'mark'. For high-order checks it * will return true of the order-0 watermark is reached and there is at least @@ -3145,19 +3168,12 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, const bool alloc_harder = (alloc_flags & (ALLOC_HARDER|ALLOC_OOM));
/* free_pages may go negative - that's OK */ - free_pages -= (1 << order) - 1; + free_pages -= __zone_watermark_unusable_free(z, order, alloc_flags);
if (alloc_flags & ALLOC_HIGH) min -= min / 2;
- /* - * If the caller does not have rights to ALLOC_HARDER then subtract - * the high-atomic reserves. This will over-estimate the size of the - * atomic reserve but it avoids a search. - */ - if (likely(!alloc_harder)) { - free_pages -= z->nr_reserved_highatomic; - } else { + if (unlikely(alloc_harder)) { /* * OOM victims can try even harder than normal ALLOC_HARDER * users on the grounds that it's definitely going to be in @@ -3170,13 +3186,6 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, min -= min / 4; }
- -#ifdef CONFIG_CMA - /* If allocation can't use CMA areas don't use free CMA pages */ - if (!(alloc_flags & ALLOC_CMA)) - free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES); -#endif - /* * Check watermarks for an order-0 allocation request. If these * are not met, then a high-order request also cannot go ahead @@ -3225,24 +3234,22 @@ bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, static inline bool zone_watermark_fast(struct zone *z, unsigned int order, unsigned long mark, int classzone_idx, unsigned int alloc_flags) { - long free_pages = zone_page_state(z, NR_FREE_PAGES); - long cma_pages = 0; + long free_pages;
-#ifdef CONFIG_CMA - /* If allocation can't use CMA areas don't use free CMA pages */ - if (!(alloc_flags & ALLOC_CMA)) - cma_pages = zone_page_state(z, NR_FREE_CMA_PAGES); -#endif + free_pages = zone_page_state(z, NR_FREE_PAGES);
/* * Fast check for order-0 only. If this fails then the reserves - * need to be calculated. There is a corner case where the check - * passes but only the high-order atomic reserve are free. If - * the caller is !atomic then it'll uselessly search the free - * list. That corner case is then slower but it is harmless. + * need to be calculated. */ - if (!order && (free_pages - cma_pages) > mark + z->lowmem_reserve[classzone_idx]) - return true; + if (!order) { + long fast_free; + + fast_free = free_pages; + fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags); + if (fast_free > mark + z->lowmem_reserve[classzone_idx]) + return true; + }
return __zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, free_pages);
From: Jaewon Kim jaewon31.kim@samsung.com
[ backport of commit 9282012fc0aa248b77a69f5eb802b67c5a16bb13 ]
There was a report that a task is waiting at the throttle_direct_reclaim. The pgscan_direct_throttle in vmstat was increasing.
This is a bug where zone_watermark_fast returns true even when the free is very low. The commit f27ce0e14088 ("page_alloc: consider highatomic reserve in watermark fast") changed the watermark fast to consider highatomic reserve. But it did not handle a negative value case which can be happened when reserved_highatomic pageblock is bigger than the actual free.
If watermark is considered as ok for the negative value, allocating contexts for order-0 will consume all free pages without direct reclaim, and finally free page may become depleted except highatomic free.
Then allocating contexts may fall into throttle_direct_reclaim. This symptom may easily happen in a system where wmark min is low and other reclaimers like kswapd does not make free pages quickly.
Handle the negative case by using MIN.
Link: https://lkml.kernel.org/r/20220725095212.25388-1-jaewon31.kim@samsung.com Fixes: f27ce0e14088 ("page_alloc: consider highatomic reserve in watermark fast") Signed-off-by: Jaewon Kim jaewon31.kim@samsung.com Reported-by: GyeongHwan Hong gh21.hong@samsung.com Acked-by: Mel Gorman mgorman@techsingularity.net Cc: Minchan Kim minchan@kernel.org Cc: Baoquan He bhe@redhat.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Yong-Taek Lee ytk.lee@samsung.com Cc: stable@vger.kerenl.org Signed-off-by: Andrew Morton akpm@linux-foundation.org --- mm/page_alloc.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 237463d..d6d8a37 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3243,11 +3243,15 @@ static inline bool zone_watermark_fast(struct zone *z, unsigned int order, * need to be calculated. */ if (!order) { - long fast_free; + long usable_free; + long reserved;
- fast_free = free_pages; - fast_free -= __zone_watermark_unusable_free(z, 0, alloc_flags); - if (fast_free > mark + z->lowmem_reserve[classzone_idx]) + usable_free = free_pages; + reserved = __zone_watermark_unusable_free(z, 0, alloc_flags); + + /* reserved may over estimate high-atomic reserves. */ + usable_free -= min(usable_free, reserved); + if (usable_free > mark + z->lowmem_reserve[classzone_idx]) return true; }
On Sun, Sep 25, 2022 at 03:35:26AM -0700, wangyong wrote:
Here are the corresponding backports to 4.19. And fix classzone_idx context differences causing patch merge conflicts.
Original commit IDS: 3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx f27ce0e page_alloc: consider highatomic reserve in watermark fast 9282012 page_alloc: fix invalid watermark check on a negative value
Changes from v1:
- Add commit information of the original patches.
None of these have your signed-off-by on them showing that the backport came from you and that you are responsible for them.
So even if we did think they were valid to backport, I can't take them as-is :(
thanks,
greg k-h
On Wed, Sep 14, 2022 at 08:46:15AM +0800, yong w wrote:
Greg KH gregkh@linuxfoundation.org 于2022年9月13日周二 21:54?道：
On Tue, Sep 13, 2022 at 09:09:47PM +0800, yong wrote:
Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
What is "this patch"? There is no context here :(
Sorry, I forgot to quote the original patch. the patch is as follows
f27ce0e page_alloc: consider highatomic reserve in watermark fastIn addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative valueIn what way? What should be done here by us?
I think these two patches should also be merged.
The classzone_idx parameter is used in the zone_watermark_fastfunctionzone, and 3334a45 use ac->high_zoneidx for classzone_idx. "9282012 page_alloc: fix invalid watermark check on a negative value" fix f27ce0e introduced issues
Ok, I need an ack by all the developers involved in those commits, as well as the subsystem maintainer so that I know it's ok to take them.
Can you provide a series of backported and tested patches so that they are easy to review?
thanks,
greg k-h
Hello I didn't know my Act is needed to merge it.
Acked-by: Jaewon Kim jaewon31.kim@samsung.com
I don't understand well why the commit f27ce0e has dependency on 3334a45, though.
Thank you Jaewon Kim
Jaewon Kim jaewon31.kim@samsung.com 于2022年9月19日周一 09:08写道：
On Wed, Sep 14, 2022 at 08:46:15AM +0800, yong w wrote:
Greg KH gregkh@linuxfoundation.org 于2022年9月13日周二 21:54?道：
On Tue, Sep 13, 2022 at 09:09:47PM +0800, yong wrote:
Hello, This patch is required to be patched in linux-5.4.y and linux-4.19.y.
What is "this patch"? There is no context here :(
Sorry, I forgot to quote the original patch. the patch is as follows
f27ce0e page_alloc: consider highatomic reserve in watermark fastIn addition to that, the following two patches are somewhat related:
3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 9282012 page_alloc: fix invalid watermark check on a negative valueIn what way? What should be done here by us?
I think these two patches should also be merged.
The classzone_idx parameter is used in the zone_watermark_fastfunctionzone, and 3334a45 use ac->high_zoneidx for classzone_idx. "9282012 page_alloc: fix invalid watermark check on a negative value" fix f27ce0e introduced issues
Ok, I need an ack by all the developers involved in those commits, as well as the subsystem maintainer so that I know it's ok to take them.
Can you provide a series of backported and tested patches so that they are easy to review?
thanks,
greg k-h
Hello I didn't know my Act is needed to merge it.
Acked-by: Jaewon Kim jaewon31.kim@samsung.com
I don't understand well why the commit f27ce0e has dependency on 3334a45, though.
Hello, the classzone_idx is used in the zone_watermark_fast function, and there will be conflicts when f27ce0e is merged.
Looking back, the following two patches adjust the classzone_idx parameter. 3334a45 mm/page_alloc: use ac->high_zoneidx for classzone_idx 97a225e mm/page_alloc: integrate classzone_idx and high_zoneidx and 3334a45 is the key modification.
Actually, I think 3334a45 can be merged or not.
Thanks.
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