On 4 August 2014 12:55, Karel Zak <kzak@xxxxxxxxxx> wrote: > On Mon, Aug 04, 2014 at 12:08:10AM +0100, Sami Kerola wrote: >> Earlier the --algorithm and --streams had to be combined with --size. To >> user requirement to combine with --size was indirectly told using >> following message. > > And is it really supported by kernel? I see in > Documentation/blockdev/zram.txt: > > 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. > > I guess that when you set disksize the zram device is "locked" for > setting changes. It means that modify already initialized (created) > zram devices is impossible. You have to reset the device to "unlock" > the device setting. After playing with zramctl I found out --algorithm must be set before --size. The --streams can be set after --size, but not if device is in use. When device is in use none of the settings are allowed. $ ./zramctl NAME ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT /dev/zram0 lzo 100K 4K 76B 4K 2 [SWAP] /dev/zram2 lzo 44K 0B 0B 0B 1 /dev/zram3 lzo 1M 40K 796B 40K 1 /mnt $ ./zramctl zram1 NAME ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT zram1 lzo 0B 0B 0B 0B 1 $ ./zramctl --algorithm lz4 zram1 ; echo $? 0 $ ./zramctl --algorithm lz4 zram2 ; echo $? zramctl: zram2: failed to set algorithm: Device or resource busy 1 $ ./zramctl --algorithm lz4 zram3 ; echo $? zramctl: zram3: failed to set algorithm: Device or resource busy 1 $ ./zramctl --stream 2 zram1 ; echo $? 0 $ ./zramctl --stream 2 zram2 ; echo $? 0 $ ./zramctl --stream 2 zram3 ; echo $? zramctl: zram3: failed to set number of streams: Invalid argument 1 Whether the case --streams 2 zram2 in above example is correct or a bug is a question to kernel developers (Sergey is CC'd). Looking the commit message http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=fe8eb122c82b2049c460fc6df6e8583a2f935cff the device behavior might be bug. -- Sami Kerola http://www.iki.fi/kerolasa/ -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
