From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751546AbdH2T0f (ORCPT ); Tue, 29 Aug 2017 15:26:35 -0400 Received: from gum.cmpxchg.org ([85.214.110.215]:53084 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751275AbdH2T0b (ORCPT ); Tue, 29 Aug 2017 15:26:31 -0400 Date: Tue, 29 Aug 2017 15:26:21 -0400 From: Johannes Weiner To: Roman Gushchin Cc: linux-mm@kvack.org, Michal Hocko , Vladimir Davydov , cgroups@vger.kernel.org, kernel-team@fb.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: memcontrol: use per-cpu stocks for socket memory uncharging Message-ID: <20170829192621.GA5447@cmpxchg.org> References: <20170829100150.4580-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170829100150.4580-1-guro@fb.com> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 29, 2017 at 11:01:50AM +0100, Roman Gushchin wrote: > We've noticed a quite sensible performance overhead on some hosts > with significant network traffic when socket memory accounting > is enabled. > > Perf top shows that socket memory uncharging path is hot: > 2.13% [kernel] [k] page_counter_cancel > 1.14% [kernel] [k] __sk_mem_reduce_allocated > 1.14% [kernel] [k] _raw_spin_lock > 0.87% [kernel] [k] _raw_spin_lock_irqsave > 0.84% [kernel] [k] tcp_ack > 0.84% [kernel] [k] ixgbe_poll > 0.83% < workload > > 0.82% [kernel] [k] enqueue_entity > 0.68% [kernel] [k] __fget > 0.68% [kernel] [k] tcp_delack_timer_handler > 0.67% [kernel] [k] __schedule > 0.60% < workload > > 0.59% [kernel] [k] __inet6_lookup_established > 0.55% [kernel] [k] __switch_to > 0.55% [kernel] [k] menu_select > 0.54% libc-2.20.so [.] __memcpy_avx_unaligned > > To address this issue, the existing per-cpu stock infrastructure > can be used. > > refill_stock() can be called from mem_cgroup_uncharge_skmem() > to move charge to a per-cpu stock instead of calling atomic > page_counter_uncharge(). > > To prevent the uncontrolled growth of per-cpu stocks, > refill_stock() will explicitly drain the cached charge, > if the cached value exceeds CHARGE_BATCH. > > This allows significantly optimize the load: > 1.21% [kernel] [k] _raw_spin_lock > 1.01% [kernel] [k] ixgbe_poll > 0.92% [kernel] [k] _raw_spin_lock_irqsave > 0.90% [kernel] [k] enqueue_entity > 0.86% [kernel] [k] tcp_ack > 0.85% < workload > > 0.74% perf-11120.map [.] 0x000000000061bf24 > 0.73% [kernel] [k] __schedule > 0.67% [kernel] [k] __fget > 0.63% [kernel] [k] __inet6_lookup_established > 0.62% [kernel] [k] menu_select > 0.59% < workload > > 0.59% [kernel] [k] __switch_to > 0.57% libc-2.20.so [.] __memcpy_avx_unaligned > > Signed-off-by: Roman Gushchin > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Vladimir Davydov > Cc: cgroups@vger.kernel.org > Cc: kernel-team@fb.com > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org Acked-by: Johannes Weiner Neat! As far as other types of pages go: page cache and anon are already batched pretty well, but I think kmem might benefit from this too. Have you considered using the stock in memcg_kmem_uncharge()?