+ zram-document-writeback_batch_size.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: zram: document writeback_batch_size
has been added to the -mm mm-new branch.  Its filename is
     zram-document-writeback_batch_size.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-document-writeback_batch_size.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: document writeback_batch_size
Date: Mon, 1 Dec 2025 18:47:50 +0900

Add missing writeback_batch_size documentation.

Link: https://lkml.kernel.org/r/20251201094754.4149975-4-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Stevens <stevensd@google.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Richard Chang <richardycc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/ABI/testing/sysfs-block-zram  |    7 +++++++
 Documentation/admin-guide/blockdev/zram.rst |   11 ++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

--- a/Documentation/ABI/testing/sysfs-block-zram~zram-document-writeback_batch_size
+++ a/Documentation/ABI/testing/sysfs-block-zram
@@ -157,3 +157,10 @@ Contact:	Richard Chang <richardycc@googl
 Description:
 		The writeback_compressed device atrribute toggles compressed
 		writeback feature.
+
+What:		/sys/block/zram<id>/writeback_batch_size
+Date:		November 2025
+Contact:	Sergey Senozhatsky <senozhatsky@chromium.org>
+Description:
+		The writeback_batch_size device atrribute sets the maximum
+		number of in-flight writeback operations.
--- a/Documentation/admin-guide/blockdev/zram.rst~zram-document-writeback_batch_size
+++ a/Documentation/admin-guide/blockdev/zram.rst
@@ -214,6 +214,8 @@ mem_limit         	WO	specifies the maxi
 writeback_limit   	WO	specifies the maximum amount of write IO zram
 				can write out to backing device as 4KB unit
 writeback_limit_enable  RW	show and set writeback_limit feature
+writeback_batch_size	RW	show and set maximum number of in-flight
+				writeback operations
 writeback_compressed	RW	show and set compressed writeback feature
 comp_algorithm    	RW	show and change the compression algorithm
 algorithm_params	WO	setup compression algorithm parameters
@@ -223,7 +225,6 @@ backing_dev	  	RW	set up backend storage
 idle		  	WO	mark allocated slot as idle
 ======================  ======  ===============================================
 
-
 User space is advised to use the following files to read the device statistics.
 
 File /sys/block/zram<id>/stat
@@ -447,6 +448,14 @@ this feature, execute::
 Note that this feature should be configured before the `zramX` device is
 initialized.
 
+Depending on backing device storage type, writeback operation may benefit
+from a higher number of in-flight write requests (batched writes).  The
+number of maximum in-flight writeback operations can be configured via
+`writeback_batch_size` attribute.  To change the default value (which is 32),
+execute::
+
+	$ echo 64 > /sys/block/zramX/writeback_batch_size
+
 If admin wants to measure writeback count in a certain period, they could
 know it via /sys/block/zram0/bd_stat's 3rd column.
 
_

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

zram-document-writeback_batch_size.patch
zram-move-bd_stat-to-writeback-section.patch
zram-rename-zram_free_page.patch
zram-switch-to-guard-for-init_lock.patch
zram-consolidate-device-attr-declarations.patch