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Diffstat (limited to 'Documentation/blockdev/zram.txt')
| -rw-r--r-- | Documentation/blockdev/zram.txt | 27 |
1 files changed, 8 insertions, 19 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 5bda5031c83d..d88f0c70cd7f 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -59,27 +59,16 @@ num_devices parameter is optional and tells zram how many devices should be pre-created. Default: 1. 2) Set max number of compression streams - Compression backend may use up to max_comp_streams compression streams, - thus allowing up to max_comp_streams concurrent compression operations. - By default, compression backend uses single compression stream. - - Examples: - #show max compression streams number + Regardless the value passed to this attribute, ZRAM will always + allocate multiple compression streams - one per online CPUs - thus + allowing several concurrent compression operations. The number of + allocated compression streams goes down when some of the CPUs + become offline. There is no single-compression-stream mode anymore, + unless you are running a UP system or has only 1 CPU online. + + To find out how many streams are currently available: cat /sys/block/zram0/max_comp_streams - #set max compression streams number to 3 - echo 3 > /sys/block/zram0/max_comp_streams - -Note: -In order to enable compression backend's multi stream support max_comp_streams -must be initially set to desired concurrency level before ZRAM device -initialisation. Once the device initialised as a single stream compression -backend (max_comp_streams equals to 1), you will see error if you try to change -the value of max_comp_streams because single stream compression backend -implemented as a special case by lock overhead issue and does not support -dynamic max_comp_streams. Only multi stream backend supports dynamic -max_comp_streams adjustment. - 3) Select compression algorithm Using comp_algorithm device attribute one can see available and currently selected (shown in square brackets) compression algorithms, |