The patch titled
Subject: zsmalloc: make sure we select best zspage size
has been added to the -mm mm-unstable branch. Its filename is
zsmalloc-make-sure-we-select-best-zspage-size.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zsmalloc-make-sure-we-select-best-zspage-size.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zsmalloc: make sure we select best zspage size
Date: Tue, 25 Oct 2022 01:12:13 +0900
We currently decide the best zspage size by looking at used percentage
value. This is not exactly enough as zspage usage percentage calculation
is not accurate.
For example, let's look at size class 208
pages per zspage wasted bytes used%
1 144 96
2 80 99
3 16 99
4 160 99
We will select 2 page per zspage configuration, as it is the first one to
reach 99%. However, 3 pages per zspage wastes less memory. Hence we need
to also consider wasted space metrics when device zspage size.
Additionally, rename max_usedpc_order because it does not hold zspage
order, it holds maximum pages per-zspage value.
Link: https://lkml.kernel.org/r/20221024161213.3221725-7-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/mm/zsmalloc.c~zsmalloc-make-sure-we-select-best-zspage-size
+++ a/mm/zsmalloc.c
@@ -775,8 +775,9 @@ out:
static int get_pages_per_zspage(struct zs_pool *pool, int class_size)
{
int i, max_usedpc = 0;
- /* zspage order which gives maximum used size per KB */
- int max_usedpc_order = 1;
+ /* zspage size which gives maximum used size per KB */
+ int pages_per_zspage = 1;
+ int min_waste = INT_MAX;
for (i = 1; i <= pool->max_pages_per_zspage; i++) {
int zspage_size;
@@ -788,14 +789,19 @@ static int get_pages_per_zspage(struct z
if (usedpc > max_usedpc) {
max_usedpc = usedpc;
- max_usedpc_order = i;
+ pages_per_zspage = i;
}
if (usedpc == 100)
break;
+
+ if (waste < min_waste) {
+ min_waste = waste;
+ pages_per_zspage = i;
+ }
}
- return max_usedpc_order;
+ return pages_per_zspage;
}
static struct zspage *get_zspage(struct page *page)
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-preparation-for-multi-zcomp-support.patch
zram-add-recompression-algorithm-sysfs-knob.patch
zram-factor-out-wb-and-non-wb-zram-read-functions.patch
zram-introduce-recompress-sysfs-knob.patch
documentation-add-recompression-documentation.patch
zram-add-recompression-algorithm-choice-to-kconfig.patch
zram-add-recompress-flag-to-read_block_state.patch
zram-clarify-writeback_store-comment.patch
zram-use-is_err_value-to-check-for-zs_malloc-errors.patch
zsmalloc-turn-zspage-order-into-runtime-variable.patch
zsmalloc-zram-pass-zspage-order-to-zs_create_pool.patch
zram-add-pool_page_order-device-attribute.patch
documentation-document-zram-pool_page_order-attribute.patch
zsmalloc-break-out-of-loop-when-found-perfect-zspage-order.patch
zsmalloc-make-sure-we-select-best-zspage-size.patch
