These counters will track hugetlb reservations rather than hugetlb memory faulted in. This patch only adds the counter, following patches add the charging and uncharging of the counter.
Problem: Currently tasks attempting to allocate more hugetlb memory than is available get a failure at mmap/shmget time. This is thanks to Hugetlbfs Reservations [1]. However, if a task attempts to allocate hugetlb memory only more than its hugetlb_cgroup limit allows, the kernel will allow the mmap/shmget call, but will SIGBUS the task when it attempts to fault the memory in.
We have developers interested in using hugetlb_cgroups, and they have expressed dissatisfaction regarding this behavior. We'd like to improve this behavior such that tasks violating the hugetlb_cgroup limits get an error on mmap/shmget time, rather than getting SIGBUS'd when they try to fault the excess memory in.
The underlying problem is that today's hugetlb_cgroup accounting happens at hugetlb memory *fault* time, rather than at *reservation* time. Thus, enforcing the hugetlb_cgroup limit only happens at fault time, and the offending task gets SIGBUS'd.
Proposed Solution: A new page counter named hugetlb.xMB.reservation_[limit|usage]_in_bytes. This counter has slightly different semantics than hugetlb.xMB.[limit|usage]_in_bytes:
- While usage_in_bytes tracks all *faulted* hugetlb memory, reservation_usage_in_bytes tracks all *reserved* hugetlb memory and hugetlb memory faulted in without a prior reservation.
- If a task attempts to reserve more memory than limit_in_bytes allows, the kernel will allow it to do so. But if a task attempts to reserve more memory than reservation_limit_in_bytes, the kernel will fail this reservation.
This proposal is implemented in this patch series, with tests to verify functionality and show the usage. We also added cgroup-v2 support to hugetlb_cgroup so that the new use cases can be extended to v2.
Alternatives considered: 1. A new cgroup, instead of only a new page_counter attached to the existing hugetlb_cgroup. Adding a new cgroup seemed like a lot of code duplication with hugetlb_cgroup. Keeping hugetlb related page counters under hugetlb_cgroup seemed cleaner as well.
2. Instead of adding a new counter, we considered adding a sysctl that modifies the behavior of hugetlb.xMB.[limit|usage]_in_bytes, to do accounting at reservation time rather than fault time. Adding a new page_counter seems better as userspace could, if it wants, choose to enforce different cgroups differently: one via limit_in_bytes, and another via reservation_limit_in_bytes. This could be very useful if you're transitioning how hugetlb memory is partitioned on your system one cgroup at a time, for example. Also, someone may find usage for both limit_in_bytes and reservation_limit_in_bytes concurrently, and this approach gives them the option to do so.
Testing: - Added tests passing. - libhugetlbfs tests mostly passing, but some tests have trouble with and without this patch series. Seems environment issue rather than code: - Overall results: ********** TEST SUMMARY * 2M * 32-bit 64-bit * Total testcases: 84 0 * Skipped: 0 0 * PASS: 66 0 * FAIL: 14 0 * Killed by signal: 0 0 * Bad configuration: 4 0 * Expected FAIL: 0 0 * Unexpected PASS: 0 0 * Test not present: 0 0 * Strange test result: 0 0 ********** - Failing tests: - elflink_rw_and_share_test("linkhuge_rw") segfaults with and without this patch series. - LD_PRELOAD=libhugetlbfs.so HUGETLB_MORECORE=yes malloc (2M: 32): FAIL Address is not hugepage - LD_PRELOAD=libhugetlbfs.so HUGETLB_RESTRICT_EXE=unknown:malloc HUGETLB_MORECORE=yes malloc (2M: 32): FAIL Address is not hugepage - LD_PRELOAD=libhugetlbfs.so HUGETLB_MORECORE=yes malloc_manysmall (2M: 32): FAIL Address is not hugepage - GLIBC_TUNABLES=glibc.malloc.tcache_count=0 LD_PRELOAD=libhugetlbfs.so HUGETLB_MORECORE=yes heapshrink (2M: 32): FAIL Heap not on hugepages - GLIBC_TUNABLES=glibc.malloc.tcache_count=0 LD_PRELOAD=libhugetlbfs.so libheapshrink.so HUGETLB_MORECORE=yes heapshrink (2M: 32): FAIL Heap not on hugepages - HUGETLB_ELFMAP=RW linkhuge_rw (2M: 32): FAIL small_data is not hugepage - HUGETLB_ELFMAP=RW HUGETLB_MINIMAL_COPY=no linkhuge_rw (2M: 32): FAIL small_data is not hugepage - alloc-instantiate-race shared (2M: 32): Bad configuration: sched_setaffinity(cpu1): Invalid argument - FAIL Child 1 killed by signal Killed - shmoverride_linked (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument - HUGETLB_SHM=yes shmoverride_linked (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument - shmoverride_linked_static (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument - HUGETLB_SHM=yes shmoverride_linked_static (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument - LD_PRELOAD=libhugetlbfs.so shmoverride_unlinked (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument - LD_PRELOAD=libhugetlbfs.so HUGETLB_SHM=yes shmoverride_unlinked (2M: 32): FAIL shmget failed size 2097152 from line 176: Invalid argument
[1]: https://www.kernel.org/doc/html/latest/vm/hugetlbfs_reserv.html
Signed-off-by: Mina Almasry almasrymina@google.com Acked-by: Hillf Danton hdanton@sina.com
--- include/linux/hugetlb.h | 23 ++++++++- mm/hugetlb_cgroup.c | 111 ++++++++++++++++++++++++++++++---------- 2 files changed, 107 insertions(+), 27 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 53fc34f930d08..9c49a0ba894d3 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -320,6 +320,27 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
#ifdef CONFIG_HUGETLB_PAGE
+enum { + /* Tracks hugetlb memory faulted in. */ + HUGETLB_RES_USAGE, + /* Tracks hugetlb memory reserved. */ + HUGETLB_RES_RESERVATION_USAGE, + /* Limit for hugetlb memory faulted in. */ + HUGETLB_RES_LIMIT, + /* Limit for hugetlb memory reserved. */ + HUGETLB_RES_RESERVATION_LIMIT, + /* Max usage for hugetlb memory faulted in. */ + HUGETLB_RES_MAX_USAGE, + /* Max usage for hugetlb memory reserved. */ + HUGETLB_RES_RESERVATION_MAX_USAGE, + /* Faulted memory accounting fail count. */ + HUGETLB_RES_FAILCNT, + /* Reserved memory accounting fail count. */ + HUGETLB_RES_RESERVATION_FAILCNT, + HUGETLB_RES_NULL, + HUGETLB_RES_MAX, +}; + #define HSTATE_NAME_LEN 32 /* Defines one hugetlb page size */ struct hstate { @@ -340,7 +361,7 @@ struct hstate { unsigned int surplus_huge_pages_node[MAX_NUMNODES]; #ifdef CONFIG_CGROUP_HUGETLB /* cgroup control files */ - struct cftype cgroup_files[5]; + struct cftype cgroup_files[HUGETLB_RES_MAX]; #endif char name[HSTATE_NAME_LEN]; }; diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index f1930fa0b445d..1ed4448ca41d3 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -25,6 +25,10 @@ struct hugetlb_cgroup { * the counter to account for hugepages from hugetlb. */ struct page_counter hugepage[HUGE_MAX_HSTATE]; + /* + * the counter to account for hugepage reservations from hugetlb. + */ + struct page_counter reserved_hugepage[HUGE_MAX_HSTATE]; };
#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val)) @@ -33,6 +37,14 @@ struct hugetlb_cgroup {
static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
+static inline struct page_counter * +hugetlb_cgroup_get_counter(struct hugetlb_cgroup *h_cg, int idx, bool reserved) +{ + if (reserved) + return &h_cg->reserved_hugepage[idx]; + return &h_cg->hugepage[idx]; +} + static inline struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s) { @@ -254,30 +266,33 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages, return; }
-enum { - RES_USAGE, - RES_LIMIT, - RES_MAX_USAGE, - RES_FAILCNT, -}; - static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { struct page_counter *counter; + struct page_counter *reserved_counter; struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)]; + reserved_counter = &h_cg->reserved_hugepage[MEMFILE_IDX(cft->private)];
switch (MEMFILE_ATTR(cft->private)) { - case RES_USAGE: + case HUGETLB_RES_USAGE: return (u64)page_counter_read(counter) * PAGE_SIZE; - case RES_LIMIT: + case HUGETLB_RES_RESERVATION_USAGE: + return (u64)page_counter_read(reserved_counter) * PAGE_SIZE; + case HUGETLB_RES_LIMIT: return (u64)counter->max * PAGE_SIZE; - case RES_MAX_USAGE: + case HUGETLB_RES_RESERVATION_LIMIT: + return (u64)reserved_counter->max * PAGE_SIZE; + case HUGETLB_RES_MAX_USAGE: return (u64)counter->watermark * PAGE_SIZE; - case RES_FAILCNT: + case HUGETLB_RES_RESERVATION_MAX_USAGE: + return (u64)reserved_counter->watermark * PAGE_SIZE; + case HUGETLB_RES_FAILCNT: return counter->failcnt; + case HUGETLB_RES_RESERVATION_FAILCNT: + return reserved_counter->failcnt; default: BUG(); } @@ -291,6 +306,7 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of, int ret, idx; unsigned long nr_pages; struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of)); + bool reserved = false;
if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */ return -EINVAL; @@ -304,9 +320,14 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of, nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));
switch (MEMFILE_ATTR(of_cft(of)->private)) { - case RES_LIMIT: + case HUGETLB_RES_RESERVATION_LIMIT: + reserved = true; + /* Fall through. */ + case HUGETLB_RES_LIMIT: mutex_lock(&hugetlb_limit_mutex); - ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages); + ret = page_counter_set_max(hugetlb_cgroup_get_counter(h_cg, idx, + reserved), + nr_pages); mutex_unlock(&hugetlb_limit_mutex); break; default: @@ -320,18 +341,26 @@ static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { int ret = 0; - struct page_counter *counter; + struct page_counter *counter, *reserved_counter; struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)]; + reserved_counter = + &h_cg->reserved_hugepage[MEMFILE_IDX(of_cft(of)->private)];
switch (MEMFILE_ATTR(of_cft(of)->private)) { - case RES_MAX_USAGE: + case HUGETLB_RES_MAX_USAGE: page_counter_reset_watermark(counter); break; - case RES_FAILCNT: + case HUGETLB_RES_RESERVATION_MAX_USAGE: + page_counter_reset_watermark(reserved_counter); + break; + case HUGETLB_RES_FAILCNT: counter->failcnt = 0; break; + case HUGETLB_RES_RESERVATION_FAILCNT: + reserved_counter->failcnt = 0; + break; default: ret = -EINVAL; break; @@ -357,37 +386,67 @@ static void __init __hugetlb_cgroup_file_init(int idx) struct hstate *h = &hstates[idx];
/* format the size */ - mem_fmt(buf, 32, huge_page_size(h)); + mem_fmt(buf, sizeof(buf), huge_page_size(h));
/* Add the limit file */ - cft = &h->cgroup_files[0]; + cft = &h->cgroup_files[HUGETLB_RES_LIMIT]; snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf); - cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_LIMIT); + cft->read_u64 = hugetlb_cgroup_read_u64; + cft->write = hugetlb_cgroup_write; + + /* Add the reservation limit file */ + cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_LIMIT]; + snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_limit_in_bytes", + buf); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_LIMIT); cft->read_u64 = hugetlb_cgroup_read_u64; cft->write = hugetlb_cgroup_write;
/* Add the usage file */ - cft = &h->cgroup_files[1]; + cft = &h->cgroup_files[HUGETLB_RES_USAGE]; snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf); - cft->private = MEMFILE_PRIVATE(idx, RES_USAGE); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_USAGE); + cft->read_u64 = hugetlb_cgroup_read_u64; + + /* Add the reservation usage file */ + cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_USAGE]; + snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_usage_in_bytes", + buf); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_USAGE); cft->read_u64 = hugetlb_cgroup_read_u64;
/* Add the MAX usage file */ - cft = &h->cgroup_files[2]; + cft = &h->cgroup_files[HUGETLB_RES_MAX_USAGE]; snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf); - cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_MAX_USAGE); + cft->write = hugetlb_cgroup_reset; + cft->read_u64 = hugetlb_cgroup_read_u64; + + /* Add the MAX reservation usage file */ + cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_MAX_USAGE]; + snprintf(cft->name, MAX_CFTYPE_NAME, + "%s.reservation_max_usage_in_bytes", buf); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_MAX_USAGE); cft->write = hugetlb_cgroup_reset; cft->read_u64 = hugetlb_cgroup_read_u64;
/* Add the failcntfile */ - cft = &h->cgroup_files[3]; + cft = &h->cgroup_files[HUGETLB_RES_FAILCNT]; snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf); - cft->private = MEMFILE_PRIVATE(idx, RES_FAILCNT); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_FAILCNT); + cft->write = hugetlb_cgroup_reset; + cft->read_u64 = hugetlb_cgroup_read_u64; + + /* Add the reservation failcntfile */ + cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_FAILCNT]; + snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_failcnt", buf); + cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_FAILCNT); cft->write = hugetlb_cgroup_reset; cft->read_u64 = hugetlb_cgroup_read_u64;
/* NULL terminate the last cft */ - cft = &h->cgroup_files[4]; + cft = &h->cgroup_files[HUGETLB_RES_NULL]; memset(cft, 0, sizeof(*cft));
WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys, -- 2.24.0.rc0.303.g954a862665-goog