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Commit 119b57ea authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Andrew Morton
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zsmalloc: document new fullness grouping 

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.orgSigned-off-by: default avatarSergey 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f76b3a32
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Showing with 74 additions and 59 deletions
Documentation/mm/zsmalloc.rst
View file @ 119b57ea
...@@ -39,13 +39,12 @@ With CONFIG_ZSMALLOC_STAT, we could see zsmalloc internal information via ...@@ -39,13 +39,12 @@ With CONFIG_ZSMALLOC_STAT, we could see zsmalloc internal information via
# cat /sys/kernel/debug/zsmalloc/zram0/classes # 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 30 512 0 12 4 1 0 1 0 0 1 0 414 3464 3346 433 1 14
10 192 1 0 2880 2872 135 3 31 528 2 7 2 2 1 0 1 0 0 2 117 4154 3793 536 4 44
11 208 0 1 819 795 42 2 32 544 6 3 4 1 2 1 0 0 0 1 260 4170 3965 556 2 26
12 224 0 1 219 159 12 4
... ...
... ...
...@@ -54,10 +53,28 @@ class ...@@ -54,10 +53,28 @@ class
index index
size size
object size zspage stores object size zspage stores
almost_empty 10%
the number of ZS_ALMOST_EMPTY zspages(see below) the number of zspages with usage ratio less than 10% (see below)
almost_full 20%
the number of ZS_ALMOST_FULL zspages(see below) 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 obj_allocated
the number of objects allocated the number of objects allocated
obj_used obj_used
...@@ -67,18 +84,11 @@ pages_used ...@@ -67,18 +84,11 @@ pages_used
pages_per_zspage pages_per_zspage
the number of 0-order pages to make a 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 Each zspage maintains inuse counter which keeps track of the number of
objects stored in the zspage. The inuse counter determines the zspage's
* n = number of allocated objects "fullness group" which is calculated as the ratio of the "inuse" objects to
* N = total number of objects zspage can store the total number of objects the zspage can hold (objs_per_zspage). The
* f = fullness_threshold_frac(ie, 4 at the moment) closer the inuse counter is to objs_per_zspage, the better.
Similarly, we assign zspage to:
* ZS_ALMOST_FULL when n > N / f
* ZS_EMPTY when n == 0
* ZS_FULL when n == N
Internals Internals
========= =========
...@@ -94,10 +104,10 @@ of objects that each zspage can store. ...@@ -94,10 +104,10 @@ of objects that each zspage can store.
For instance, consider the following size classes::: 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 94 1536 0 .... 0 0 0 0 3 0
100 1632 0 0 0 0 0 2 0 100 1632 0 .... 0 0 0 0 2 0
... ...
...@@ -134,10 +144,11 @@ reduces memory wastage. ...@@ -134,10 +144,11 @@ reduces memory wastage.
Let's take a closer look at the bottom of `/sys/kernel/debug/zsmalloc/zramX/classes`::: 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 0 202 3264 0 .. 0 0 0 0 4 0
254 4096 0 0 0 0 0 1 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 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. ...@@ -151,40 +162,42 @@ efficient storage of large objects.
For zspage chain size of 8, huge class watermark becomes 3632 bytes::: 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 0 202 3264 0 .. 0 0 0 0 4 0
211 3408 0 0 0 0 0 5 0 211 3408 0 .. 0 0 0 0 5 0
217 3504 0 0 0 0 0 6 0 217 3504 0 .. 0 0 0 0 6 0
222 3584 0 0 0 0 0 7 0 222 3584 0 .. 0 0 0 0 7 0
225 3632 0 0 0 0 0 8 0 225 3632 0 .. 0 0 0 0 8 0
254 4096 0 0 0 0 0 1 0 254 4096 0 .. 0 0 0 0 1 0
... ...
For zspage chain size of 16, huge class watermark becomes 3840 bytes::: 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 0 202 3264 0 .. 0 0 0 0 4 0
206 3328 0 0 0 0 0 13 0 206 3328 0 .. 0 0 0 0 13 0
207 3344 0 0 0 0 0 9 0 207 3344 0 .. 0 0 0 0 9 0
208 3360 0 0 0 0 0 14 0 208 3360 0 .. 0 0 0 0 14 0
211 3408 0 0 0 0 0 5 0 211 3408 0 .. 0 0 0 0 5 0
212 3424 0 0 0 0 0 16 0 212 3424 0 .. 0 0 0 0 16 0
214 3456 0 0 0 0 0 11 0 214 3456 0 .. 0 0 0 0 11 0
217 3504 0 0 0 0 0 6 0 217 3504 0 .. 0 0 0 0 6 0
219 3536 0 0 0 0 0 13 0 219 3536 0 .. 0 0 0 0 13 0
222 3584 0 0 0 0 0 7 0 222 3584 0 .. 0 0 0 0 7 0
223 3600 0 0 0 0 0 15 0 223 3600 0 .. 0 0 0 0 15 0
225 3632 0 0 0 0 0 8 0 225 3632 0 .. 0 0 0 0 8 0
228 3680 0 0 0 0 0 9 0 228 3680 0 .. 0 0 0 0 9 0
230 3712 0 0 0 0 0 10 0 230 3712 0 .. 0 0 0 0 10 0
232 3744 0 0 0 0 0 11 0 232 3744 0 .. 0 0 0 0 11 0
234 3776 0 0 0 0 0 12 0 234 3776 0 .. 0 0 0 0 12 0
235 3792 0 0 0 0 0 13 0 235 3792 0 .. 0 0 0 0 13 0
236 3808 0 0 0 0 0 14 0 236 3808 0 .. 0 0 0 0 14 0
238 3840 0 0 0 0 0 15 0 238 3840 0 .. 0 0 0 0 15 0
254 4096 0 0 0 0 0 1 0 254 4096 0 .. 0 0 0 0 1 0
... ...
Overall the combined zspage chain size effect on zsmalloc pool configuration::: Overall the combined zspage chain size effect on zsmalloc pool configuration:::
...@@ -214,9 +227,10 @@ zram as a build artifacts storage (Linux kernel compilation). ...@@ -214,9 +227,10 @@ zram as a build artifacts storage (Linux kernel compilation).
zsmalloc classes stats::: 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::: zram mm_stat:::
...@@ -227,9 +241,10 @@ zram as a build artifacts storage (Linux kernel compilation). ...@@ -227,9 +241,10 @@ zram as a build artifacts storage (Linux kernel compilation).
zsmalloc classes stats::: 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::: zram mm_stat:::
......
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