The quilt patch titled Subject: zsmalloc: document new fullness grouping has been removed from the -mm tree. Its filename was zsmalloc-document-new-fullness-grouping.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------ From: Sergey Senozhatsky senozhatsky@chromium.org Subject: zsmalloc: document new fullness grouping Date: Sat, 25 Mar 2023 11:46:30 +0900

Patch series "zsmalloc: minor documentation updates".

Two minor patches that bring zsmalloc documentation up to date.

This patch (of 2):

Update documentation and reflect new zspages fullness grouping (we don't use almost_empty and almost_full anymore).

Link: https://lkml.kernel.org/r/20230325024631.2817153-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20230325024631.2817153-2-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky senozhatsky@chromium.org Fixes: 67e157eb3639 ("zsmalloc: show per fullness group class stats") Cc: Minchan Kim minchan@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

Documentation/mm/zsmalloc.rst | 133 +++++++++++++++++--------------- 1 file changed, 74 insertions(+), 59 deletions(-)

--- a/Documentation/mm/zsmalloc.rst~zsmalloc-document-new-fullness-grouping +++ a/Documentation/mm/zsmalloc.rst @@ -39,13 +39,12 @@ With CONFIG_ZSMALLOC_STAT, we could see

# cat /sys/kernel/debug/zsmalloc/zram0/classes

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage + class size 10% 20% 30% 40% 50% 60% 70% 80% 90% 99% 100% obj_allocated obj_used pages_used pages_per_zspage freeable ... ... - 9 176 0 1 186 129 8 4 - 10 192 1 0 2880 2872 135 3 - 11 208 0 1 819 795 42 2 - 12 224 0 1 219 159 12 4 + 30 512 0 12 4 1 0 1 0 0 1 0 414 3464 3346 433 1 14 + 31 528 2 7 2 2 1 0 1 0 0 2 117 4154 3793 536 4 44 + 32 544 6 3 4 1 2 1 0 0 0 1 260 4170 3965 556 2 26 ... ...

@@ -54,10 +53,28 @@ class index size object size zspage stores -almost_empty - the number of ZS_ALMOST_EMPTY zspages(see below) -almost_full - the number of ZS_ALMOST_FULL zspages(see below) +10% + the number of zspages with usage ratio less than 10% (see below) +20% + the number of zspages with usage ratio between 10% and 20% +30% + the number of zspages with usage ratio between 20% and 30% +40% + the number of zspages with usage ratio between 30% and 40% +50% + the number of zspages with usage ratio between 40% and 50% +60% + the number of zspages with usage ratio between 50% and 60% +70% + the number of zspages with usage ratio between 60% and 70% +80% + the number of zspages with usage ratio between 70% and 80% +90% + the number of zspages with usage ratio between 80% and 90% +99% + the number of zspages with usage ratio between 90% and 99% +100% + the number of zspages with usage ratio 100% obj_allocated the number of objects allocated obj_used @@ -67,18 +84,11 @@ pages_used pages_per_zspage the number of 0-order pages to make a zspage

-We assign a zspage to ZS_ALMOST_EMPTY fullness group when n <= N / f, where - -* n = number of allocated objects -* N = total number of objects zspage can store -* f = fullness_threshold_frac(ie, 4 at the moment) - -Similarly, we assign zspage to: - -* ZS_ALMOST_FULL when n > N / f -* ZS_EMPTY when n == 0 -* ZS_FULL when n == N - +Each zspage maintains inuse counter which keeps track of the number of +objects stored in the zspage. The inuse counter determines the zspage's +"fullness group" which is calculated as the ratio of the "inuse" objects to +the total number of objects the zspage can hold (objs_per_zspage). The +closer the inuse counter is to objs_per_zspage, the better.

Internals ========= @@ -94,10 +104,10 @@ of objects that each zspage can store.

For instance, consider the following size classes:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable ... - 94 1536 0 0 0 0 0 3 0 - 100 1632 0 0 0 0 0 2 0 + 94 1536 0 .... 0 0 0 0 3 0 + 100 1632 0 .... 0 0 0 0 2 0 ...

@@ -134,10 +144,11 @@ reduces memory wastage.

Let's take a closer look at the bottom of `/sys/kernel/debug/zsmalloc/zramX/classes`:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable + ... - 202 3264 0 0 0 0 0 4 0 - 254 4096 0 0 0 0 0 1 0 + 202 3264 0 .. 0 0 0 0 4 0 + 254 4096 0 .. 0 0 0 0 1 0 ...

Size class #202 stores objects of size 3264 bytes and has a maximum of 4 pages @@ -151,40 +162,42 @@ efficient storage of large objects.

For zspage chain size of 8, huge class watermark becomes 3632 bytes:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable + ... - 202 3264 0 0 0 0 0 4 0 - 211 3408 0 0 0 0 0 5 0 - 217 3504 0 0 0 0 0 6 0 - 222 3584 0 0 0 0 0 7 0 - 225 3632 0 0 0 0 0 8 0 - 254 4096 0 0 0 0 0 1 0 + 202 3264 0 .. 0 0 0 0 4 0 + 211 3408 0 .. 0 0 0 0 5 0 + 217 3504 0 .. 0 0 0 0 6 0 + 222 3584 0 .. 0 0 0 0 7 0 + 225 3632 0 .. 0 0 0 0 8 0 + 254 4096 0 .. 0 0 0 0 1 0 ...

For zspage chain size of 16, huge class watermark becomes 3840 bytes:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable + ... - 202 3264 0 0 0 0 0 4 0 - 206 3328 0 0 0 0 0 13 0 - 207 3344 0 0 0 0 0 9 0 - 208 3360 0 0 0 0 0 14 0 - 211 3408 0 0 0 0 0 5 0 - 212 3424 0 0 0 0 0 16 0 - 214 3456 0 0 0 0 0 11 0 - 217 3504 0 0 0 0 0 6 0 - 219 3536 0 0 0 0 0 13 0 - 222 3584 0 0 0 0 0 7 0 - 223 3600 0 0 0 0 0 15 0 - 225 3632 0 0 0 0 0 8 0 - 228 3680 0 0 0 0 0 9 0 - 230 3712 0 0 0 0 0 10 0 - 232 3744 0 0 0 0 0 11 0 - 234 3776 0 0 0 0 0 12 0 - 235 3792 0 0 0 0 0 13 0 - 236 3808 0 0 0 0 0 14 0 - 238 3840 0 0 0 0 0 15 0 - 254 4096 0 0 0 0 0 1 0 + 202 3264 0 .. 0 0 0 0 4 0 + 206 3328 0 .. 0 0 0 0 13 0 + 207 3344 0 .. 0 0 0 0 9 0 + 208 3360 0 .. 0 0 0 0 14 0 + 211 3408 0 .. 0 0 0 0 5 0 + 212 3424 0 .. 0 0 0 0 16 0 + 214 3456 0 .. 0 0 0 0 11 0 + 217 3504 0 .. 0 0 0 0 6 0 + 219 3536 0 .. 0 0 0 0 13 0 + 222 3584 0 .. 0 0 0 0 7 0 + 223 3600 0 .. 0 0 0 0 15 0 + 225 3632 0 .. 0 0 0 0 8 0 + 228 3680 0 .. 0 0 0 0 9 0 + 230 3712 0 .. 0 0 0 0 10 0 + 232 3744 0 .. 0 0 0 0 11 0 + 234 3776 0 .. 0 0 0 0 12 0 + 235 3792 0 .. 0 0 0 0 13 0 + 236 3808 0 .. 0 0 0 0 14 0 + 238 3840 0 .. 0 0 0 0 15 0 + 254 4096 0 .. 0 0 0 0 1 0 ...

Overall the combined zspage chain size effect on zsmalloc pool configuration::: @@ -214,9 +227,10 @@ zram as a build artifacts storage (Linux

zsmalloc classes stats:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable + ... - Total 13 51 413836 412973 159955 3 + Total 13 .. 51 413836 412973 159955 3

zram mm_stat:::

@@ -227,9 +241,10 @@ zram as a build artifacts storage (Linux

zsmalloc classes stats:::

- class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable + class size 10% .... 100% obj_allocated obj_used pages_used pages_per_zspage freeable + ... - Total 18 87 414852 412978 156666 0 + Total 18 .. 87 414852 412978 156666 0

zram mm_stat:::

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Patches currently in -mm which might be from senozhatsky@chromium.org are