On Mon, Jul 07, 2014 at 07:40:08PM +0400, Vladimir Davydov wrote: > On Mon, Jul 07, 2014 at 10:25:06AM -0400, Johannes Weiner wrote: > > You could then reap dead slab caches as part of the regular per-memcg > > slab scanning in reclaim, without having to resort to auxiliary lists, > > vmpressure events etc. > > Do you mean adding a per memcg shrinker that will call kmem_cache_shrink > for all memcg caches on memcg/global pressure? > > Actually I recently made dead caches self-destructive at the cost of > slowing down kfrees to dead caches (see > https://www.lwn.net/Articles/602330/, it's already in the mmotm tree) so > no dead cache reaping is necessary. Do you think if we need it now? > > > I think it would save us a lot of code and complexity. You want > > per-memcg slab scanning *anyway*, all we'd have to change in the > > existing code would be to pin the css until the LRUs and kmem caches > > are truly empty, and switch mem_cgroup_iter() to css_tryget(). > > > > Would this make sense to you? > > Hmm, interesting. Thank you for such a thorough explanation. > > One question. Do we still need to free mem_cgroup->kmemcg_id on css > offline so that it can be reused by new kmem-active cgroups (currently > we don't)? > > If we won't free it the root_cache->memcg_params->memcg_arrays may > become really huge due to lots of dead css holding the id.
We only need the O(1) access of the array for allocation - not frees and reclaim, right? So with your self-destruct code, can we prune caches of dead css and then just remove them from the array? Or move them from the array to a per-memcg linked list that can be scanned on memcg memory pressure? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
