| Message ID | 20221031054108.541190-9-senozhatsky@chromium.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | zsmalloc/zram: configurable zspage size | expand |
On Mon, Oct 31, 2022 at 02:41:07PM +0900, Sergey Senozhatsky wrote: > Provide a simple documentation for pages_per_pool_page ZRAM > device attribute. > > Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> > --- > Documentation/admin-guide/blockdev/zram.rst | 38 ++++++++++++++++----- > 1 file changed, 30 insertions(+), 8 deletions(-) > > diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst > index 010fb05a5999..4cb287520d45 100644 > --- a/Documentation/admin-guide/blockdev/zram.rst > +++ b/Documentation/admin-guide/blockdev/zram.rst > @@ -112,7 +112,29 @@ to list all of them using, for instance, /proc/crypto or any other > method. This, however, has an advantage of permitting the usage of > custom crypto compression modules (implementing S/W or H/W compression). > > -4) Set Disksize > +4) Set pages per-pool page limit: Optional > +========================================== > + > +zsmalloc pages can consist of up to ZS_DEFAULT_PAGES_PER_ZSPAGE (single) > +physical pages. The exact number is calculated for each zsmalloc size > +class during zsmalloc pool creation. ZRAM provides pages_per_pool_page > +device attribute that lets one adjust that limit (maximum possible value > +is ZS_MAX_PAGES_PER_ZSPAGE). The default limit is considered to be good > +enough, so tweak this value only when the changes in zsmalloc size classes > +characteristics are beneficial for your data patterns. The limit on the > +pages per zspages (currently) should be in [1,16] range; default value > +is 4. I think we need to introudce pros and cons for user to decide it since it's not familiar with admin. I think It would need more explanation about zsmalloc internal(especailly zspage and size classes)
On (22/11/10 18:20), Minchan Kim wrote: > > diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst > > index 010fb05a5999..4cb287520d45 100644 > > --- a/Documentation/admin-guide/blockdev/zram.rst > > +++ b/Documentation/admin-guide/blockdev/zram.rst > > @@ -112,7 +112,29 @@ to list all of them using, for instance, /proc/crypto or any other > > method. This, however, has an advantage of permitting the usage of > > custom crypto compression modules (implementing S/W or H/W compression). > > > > -4) Set Disksize > > +4) Set pages per-pool page limit: Optional > > +========================================== > > + > > +zsmalloc pages can consist of up to ZS_DEFAULT_PAGES_PER_ZSPAGE (single) > > +physical pages. The exact number is calculated for each zsmalloc size > > +class during zsmalloc pool creation. ZRAM provides pages_per_pool_page > > +device attribute that lets one adjust that limit (maximum possible value > > +is ZS_MAX_PAGES_PER_ZSPAGE). The default limit is considered to be good > > +enough, so tweak this value only when the changes in zsmalloc size classes > > +characteristics are beneficial for your data patterns. The limit on the > > +pages per zspages (currently) should be in [1,16] range; default value > > +is 4. > > I think we need to introudce pros and cons for user to decide it since > it's not familiar with admin. I think It would need more explanation about > zsmalloc internal(especailly zspage and size classes) OK, agreed. I have quite a bit of info in the 0002 commit messages. I can copy-paste some of those bits and edit them. We also have some info the internal doc, which I can also use as a "source of inspiration".
diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 010fb05a5999..4cb287520d45 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -112,7 +112,29 @@ to list all of them using, for instance, /proc/crypto or any other method. This, however, has an advantage of permitting the usage of custom crypto compression modules (implementing S/W or H/W compression). -4) Set Disksize +4) Set pages per-pool page limit: Optional +========================================== + +zsmalloc pages can consist of up to ZS_DEFAULT_PAGES_PER_ZSPAGE (single) +physical pages. The exact number is calculated for each zsmalloc size +class during zsmalloc pool creation. ZRAM provides pages_per_pool_page +device attribute that lets one adjust that limit (maximum possible value +is ZS_MAX_PAGES_PER_ZSPAGE). The default limit is considered to be good +enough, so tweak this value only when the changes in zsmalloc size classes +characteristics are beneficial for your data patterns. The limit on the +pages per zspages (currently) should be in [1,16] range; default value +is 4. + +Examples:: + + #show current zsmalloc pages per-pool page limit + cat /sys/block/zramX/pages_per_pool_page + 4 + + #set zsmalloc pages per-pool page limit + echo 8 > /sys/block/zramX/pages_per_pool_page + +5) Set Disksize =============== Set disk size by writing the value to sysfs node 'disksize'. @@ -132,7 +154,7 @@ There is little point creating a zram of greater than twice the size of memory since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the size of the disk when not in use so a huge zram is wasteful. -5) Set memory limit: Optional +6) Set memory limit: Optional ============================= Set memory limit by writing the value to sysfs node 'mem_limit'. @@ -151,7 +173,7 @@ Examples:: # To disable memory limit echo 0 > /sys/block/zram0/mem_limit -6) Activate +7) Activate =========== :: @@ -162,7 +184,7 @@ Examples:: mkfs.ext4 /dev/zram1 mount /dev/zram1 /tmp -7) Add/remove zram devices +8) Add/remove zram devices ========================== zram provides a control interface, which enables dynamic (on-demand) device @@ -182,7 +204,7 @@ execute:: echo X > /sys/class/zram-control/hot_remove -8) Stats +9) Stats ======== Per-device statistics are exported as various nodes under /sys/block/zram<id>/ @@ -283,15 +305,15 @@ a single line of text and contains the following stats separated by whitespace: Unit: 4K bytes ============== ============================================================= -9) Deactivate -============= +10) Deactivate +============== :: swapoff /dev/zram0 umount /dev/zram1 -10) Reset +11) Reset ========= Write any positive value to 'reset' sysfs node::
Provide a simple documentation for pages_per_pool_page ZRAM device attribute. Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> --- Documentation/admin-guide/blockdev/zram.rst | 38 ++++++++++++++++----- 1 file changed, 30 insertions(+), 8 deletions(-)