On Mon, Nov 30, 2015 at 10:26:38AM -0500, Johannes Weiner wrote: > On Mon, Nov 30, 2015 at 01:54:21PM +0300, Vladimir Davydov wrote: > > On Tue, Nov 24, 2015 at 04:58:44PM -0500, Johannes Weiner wrote: > > ... > > > @@ -5520,15 +5557,30 @@ void sock_release_memcg(struct sock *sk) > > > */ > > > bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) > > > { > > > - struct page_counter *counter; > > > + gfp_t gfp_mask = GFP_KERNEL; > > > > > > - if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated, > > > - nr_pages, &counter)) { > > > - memcg->tcp_mem.memory_pressure = 0; > > > - return true; > > > +#ifdef CONFIG_MEMCG_KMEM > > > + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > > > + struct page_counter *counter; > > > + > > > + if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated, > > > + nr_pages, &counter)) { > > > + memcg->tcp_mem.memory_pressure = 0; > > > + return true; > > > + } > > > + page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages); > > > + memcg->tcp_mem.memory_pressure = 1; > > > + return false; > > > } > > > - page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages); > > > - memcg->tcp_mem.memory_pressure = 1; > > > +#endif > > > + /* Don't block in the packet receive path */ > > > + if (in_softirq()) > > > + gfp_mask = GFP_NOWAIT; > > > + > > > + if (try_charge(memcg, gfp_mask, nr_pages) == 0) > > > + return true; > > > + > > > + try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages); > > > > We won't trigger high reclaim if we get here, because try_charge does > > not check high threshold if failing or forcing charge. I think this > > should be fixed regardless of this patch. The fix is attached below. > > We kind of assume that max is either set above high, or not at > all. That means when max is hit the high limit has already failed and > it's of limited use to schedule background reclaim. Yeah, you're right. No point scheduling the work here - it must be already running. > > > Also, I don't like calling try_charge twice: the second time will go > > through all the try_charge steps for nothing. What about checking > > page_counter value after calling try_charge instead: > > > > try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages); > > return page_counter_read(&memcg->memory) <= memcg->memory.limit; > > > > or adding an out parameter to try_charge that would inform us if charge > > was forced? > > That's a complete cold path where we are going to drop the packet in > all but a few cases. It's not worth the trouble. Right > > > > @@ -5539,10 +5591,32 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) > > > */ > > > void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) > > > { > > > - page_counter_uncharge(&memcg->tcp_mem.memory_allocated, nr_pages); > > > +#ifdef CONFIG_MEMCG_KMEM > > > + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > > > + page_counter_uncharge(&memcg->tcp_mem.memory_allocated, > > > + nr_pages); > > > + return; > > > + } > > > +#endif > > > + page_counter_uncharge(&memcg->memory, nr_pages); > > > + css_put_many(&memcg->css, nr_pages); > > > > cancel_charge(memcg, nr_pages); > > It does the same, but it's a weird name for regular uncharging. Right > > > From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> > > Subject: [PATCH] memcg: check high threshold if forcing allocation > > > > try_charge() does not result in checking high threshold if it forces > > charge. This is incorrect, because we could have failed to reclaim > > memory due to the current context, so we do need to check high threshold > > and try to compensate for the excess once we are in the safe context. > > > > Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 79a29d564bff..e922965b572b 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2112,13 +2112,14 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > > page_counter_charge(&memcg->memsw, nr_pages); > > css_get_many(&memcg->css, nr_pages); > > > > - return 0; > > + goto check_high; > > > > done_restock: > > css_get_many(&memcg->css, batch); > > if (batch > nr_pages) > > refill_stock(memcg, batch - nr_pages); > > > > +check_high: > > /* > > * If the hierarchy is above the normal consumption range, schedule > > * reclaim on returning to userland. We can perform reclaim here > > One problem is that OOM victims force their charges so they can exit > quickly. It'd be contradictory to then task them with high reclaim. > Yeah, scratch that patch. It isn't necessary anyway, because, as you pointed out, we don't really need to schedule high reclaim when we fail hard in mem_cgroup_charge_skmem. No more questions left, Reviewed-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> 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>