Mikael can be right. Each slab is 1mb and its designated to hold items of particualr size. So if you had 5000 items over 500KB inserted into the cache at some time ( at the beginning ) they would consume 5GB (they would take 1MB each even if they were 501KB).
So after some time caching patterns change and you dont insert big items any more. This 5GB is wasted if you are not using such big items any more. So distribution changes and big items are not needed any more but more smaller items cant fit into the cache as memcached cant put small items into slabs designated for big items. Sorry if my explanation is not super good :) checkout this tool out though http://artur.ejsmont.org/blog/content/first-version-of-memcache-stats-script-based-on-memcachephp i took a open source stats scripts and added detailed view of slabs. It should tell you how many slabs you have allocated per size and how many items are there. I guess this should give you good idea what is really happening. :- ) art On 5 November 2010 05:59, vishnu <vishnudee...@gmail.com> wrote: > What is slab distribution? > > How can i resolve this issue? > > Thanks. > > On Thu, Nov 4, 2010 at 10:40 PM, dormando <dorma...@rydia.net> wrote: >> >> reclaims are good, evictions are bad >> >> On Thu, 4 Nov 2010, Kate Wang wrote: >> >> > We are experiencing high reclaims instead of evictions. Could slab >> > distribution shift cause that as well? >> > >> > If the slab distribution shifted could cause high eviction rate, what's >> > the best way to fix it or avoid it? >> > >> > Thanks! >> > >> > On Thu, Nov 4, 2010 at 5:52 PM, Mikael Fridh <fri...@gmail.com> wrote: >> > On Nov 4, 6:32 pm, rahul_kcle <vishnudee...@gmail.com> wrote: >> > > >> > > From last 2 weeks i am seeing evictions happening on our >> > memcached >> > > boxes even though there is lot of memory left . Here are the >> > stats >> > > from memcached >> > > >> > > STAT bytes_read 434627188758 >> > > STAT bytes_written 357821569260 >> > > STAT limit_maxbytes 23622320128 >> > > STAT accepting_conns 1 >> > > STAT listen_disabled_num 0 >> > > STAT threads 5 >> > > STAT conn_yields 0 >> > > STAT bytes 14573115225 >> > > STAT curr_items 1853350 >> > > STAT total_items 66439158 >> > > STAT evictions 7000591 >> > > >> > > Bytes is much lessser than limit_maxbytes. >> > >> > See stats slabs, possibly your slab distribution profile have shifted >> > over time. >> > >> > Mikael >> > >> > >> > >> > > -- Visit me at: http://artur.ejsmont.org/blog/
