Re: [PATCH 0/3] Make workingset detection logic memcg aware
From: Vladimir Davydov
Date: Mon Aug 10 2015 - 04:14:38 EST
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
> >>ããããeviction | 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
> It doesn't matter, we can use lazy counter like pcpu counter because it's not needed to be very accurate.
> >> 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
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/