Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[deliverable/linux.git] / Documentation / blockdev / zram.txt

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 5bda5031c83de2b6e85ff2a6fe8bb3a8107a4aa5..13100fb3c26df99317a6ddd8acc9ec0fa85ed0dd 100644 (file)
--- 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,
@@ -183,6 +172,7 @@ mem_limit         RW    the maximum amount of memory ZRAM can use to store
 pages_compacted   RO    the number of pages freed during compaction
                         (available only via zram<id>/mm_stat node)
 compact           WO    trigger memory compaction
+debug_stat        RO    this file is used for zram debugging purposes
 
 WARNING
 =======