From 2502673aed6c66befc7efc2dc008e2a8a50508cd Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Mon, 1 Dec 2025 18:47:50 +0900 Subject: zram: document writeback_batch_size Add missing writeback_batch_size documentation. Link: https://lkml.kernel.org/r/20251201094754.4149975-4-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky Cc: Brian Geffon Cc: David Stevens Cc: Minchan Kim Cc: Richard Chang Signed-off-by: Andrew Morton --- Documentation/admin-guide/blockdev/zram.rst | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'Documentation/admin-guide/blockdev') diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 9547e4e95979..94bb7f2245ee 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -214,6 +214,8 @@ mem_limit WO specifies the maximum amount of memory ZRAM can 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 for zram to write out 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/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. -- cgit v1.2.3