The patch titled
Subject: zram: don't retry compress incompressible page
has been added to the -mm mm-unstable branch. Its filename is
zram-dont-retry-compress-incompressible-page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-dont-retry-compress-incompressible-page.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: Alexey Romanov <avromanov@xxxxxxxxxxxxxx>
Subject: zram: don't retry compress incompressible page
Date: Wed, 10 Aug 2022 14:28:57 +0300
It doesn't make sense for us to retry to compress an uncompressible page
(comp_len == PAGE_SIZE) in zsmalloc slowpath, because we will be storing
it uncompressed anyway. We can avoid wasting time on another compression
attempt. It is enough to take lock (zcomp_stream_get) and execute the
code below.
Link: https://lkml.kernel.org/r/20220810112857.90278-1-avromanov@xxxxxxxxxxxxxx
Signed-off-by: Alexey Romanov <avromanov@xxxxxxxxxxxxxx>
Signed-off-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-dont-retry-compress-incompressible-page
+++ a/drivers/block/zram/zram_drv.c
@@ -1410,9 +1410,20 @@ compress_again:
handle = zs_malloc(zram->mem_pool, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
__GFP_MOVABLE);
- if (!IS_ERR((void *)handle))
+ if (IS_ERR((void *)handle))
+ return PTR_ERR((void *)handle);
+
+ if (comp_len != PAGE_SIZE)
goto compress_again;
- return PTR_ERR((void *)handle);
+
+ /*
+ * If the page is not compressible, you need to acquire the lock and
+ * execute the code below. The zcomp_stream_get() call is needed to
+ * disable the cpu hotplug and grab the zstrm buffer back.
+ * It is necessary that the dereferencing of the zstrm variable below
+ * occurs correctly.
+ */
+ zstrm = zcomp_stream_get(zram->comp);
}
alloced_pages = zs_get_total_pages(zram->mem_pool);
_
Patches currently in -mm which might be from avromanov@xxxxxxxxxxxxxx are
zsmalloc-zs_object_copy-add-clarifying-comment.patch
zsmalloc-remove-unnecessary-size_class-null-check.patch
zsmalloc-zs_object_copy-replace-email-link-to-doc.patch
zram-dont-retry-compress-incompressible-page.patch
