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Diffstat (limited to 'Documentation/admin-guide/blockdev/zram.rst')
| -rw-r--r-- | Documentation/admin-guide/blockdev/zram.rst | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 3e273c1bb749..94bb7f2245ee 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -214,6 +214,9 @@ 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 compact WO trigger memory compaction @@ -222,7 +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<id>/stat @@ -434,6 +436,26 @@ system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback happened until you reset the zram to allocate extra writeback budget in next setting is user's job. +By default zram stores written back pages in decompressed (raw) form, which +means that writeback operation involves decompression of the page before +writing it to the backing device. This behavior can be changed by enabling +`writeback_compressed` feature, which causes zram to write compressed pages +to the backing device, thus avoiding decompression overhead. To enable +this feature, execute:: + + $ echo yes > /sys/block/zramX/writeback_compressed + +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. |