On Sun, Aug 09, 2015 at 11:12:25PM +0900, Kamezawa Hiroyuki wrote: > On 2015/08/08 22:05, Vladimir Davydov wrote: > >On Fri, Aug 07, 2015 at 10:38:16AM +0900, Kamezawa Hiroyuki wrote: ... > >>All ? hmm. It seems that mixture of record of global memory pressure and of local memory > >>pressure is just wrong. > > > >What makes you think so? An example of misbehavior caused by this would > >be nice to have. > > > > By design, memcg's LRU aging logic is independent from global memory allocation/pressure. > > > Assume there are 4 containers(using much page-cache) with 1GB limit on 4GB server, > # contaienr A workingset=600M limit=1G (sleepy) > # contaienr B workingset=300M limit=1G (work often) > # container C workingset=500M limit=1G (work slowly) > # container D workingset=1.2G limit=1G (work hard) > container D can drive the zone's distance counter because of local memory reclaim. > If active/inactive = 1:1, container D page can be activated. > At kswapd(global reclaim) runs, all container's LRU will rotate. > > Possibility of refault in A, B, C is reduced by conainer D's counter updates. This does not necessarily mean we have to use different inactive_age counter for global and local memory pressure. In your example, having inactive_age per lruvec and using it for evictions on both global and local memory pressure would work just fine. > > But yes, some _real_ test are required. > > >> > >>Now, the record is > >> > >> eviction | node | zone | 2bit. > >> > >>How about changing this as > >> > >> 0 |eviction | node | zone | 2bit > >> 1 |eviction | memcgid | 2bit > >> > >>Assume each memcg has an eviction counter, which ignoring node/zone. > >>i.e. memcg local reclaim happens against memcg not against zone. > >> > >>At page-in, > >> if (the 1st bit is 0) > >> compare eviction counter with zone's counter and activate the page if needed. > >> else if (the 1st bit is 1) > >> compare eviction counter with the memcg (if exists) > > > >Having a single counter per memcg won't scale with the number of NUMA > >nodes. > > > It doesn't matter, we can use lazy counter like pcpu counter because it's not needed to be very accurate. Fair enough. > > > >> if (current memcg == recorded memcg && eviction distance is okay) > >> activate page. > >> else > >> inactivate > >>At page-out > >> if (global memory pressure) > >> record eviction id with using zone's counter. > >> else if (memcg local memory pressure) > >> record eviction id with memcg's counter. > >> > > > >I don't understand how this is supposed to work when a memory cgroup > >experiences both local and global pressure simultaneously. > > > > I think updating global distance counter by local reclaim may update counter too much. But if the inactive_age counter was per lruvec, then we wouldn't need to bother about it. > Above is to avoid updating zone's counter and keep memcg's LRU active/inactive balanced. > > >Also, what if a memory cgroup is protected by memory.low? Such a cgroup > >may have all its pages in the active list, because it is never scanned. > > If LRU never scanned, all file caches tend to be in INACTIVE...it never refaults. This is not true - there still may be activations from mark_page_accessed. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>