From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 6555D6B026A for ; Fri, 29 Sep 2017 04:15:12 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id y29so1775174pff.6 for ; Fri, 29 Sep 2017 01:15:12 -0700 (PDT) Received: from EUR01-VE1-obe.outbound.protection.outlook.com (mail-ve1eur01on0102.outbound.protection.outlook.com. [104.47.1.102]) by mx.google.com with ESMTPS id h5si3039091pln.249.2017.09.29.01.15.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 29 Sep 2017 01:15:10 -0700 (PDT) Subject: Re: [PATCH] mm: Make count list_lru_one::nr_items lockless References: <150583358557.26700.8490036563698102569.stgit@localhost.localdomain> <20170927141530.25286286fb92a2573c4b548f@linux-foundation.org> <20170928140230.a9a0cd44a09eae9441a83bdc@linux-foundation.org> From: Kirill Tkhai Message-ID: <137a49f9-8286-8bf4-91c5-37b5f6b5a842@virtuozzo.com> Date: Fri, 29 Sep 2017 11:15:04 +0300 MIME-Version: 1.0 In-Reply-To: <20170928140230.a9a0cd44a09eae9441a83bdc@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: vdavydov.dev@gmail.com, apolyakov@beget.ru, linux-kernel@vger.kernel.org, linux-mm@kvack.org, aryabinin@virtuozzo.com On 29.09.2017 00:02, Andrew Morton wrote: > On Thu, 28 Sep 2017 10:48:55 +0300 Kirill Tkhai wrote: > >>>> This patch aims to make super_cache_count() (and other functions, >>>> which count LRU nr_items) more effective. >>>> It allows list_lru_node::memcg_lrus to be RCU-accessed, and makes >>>> __list_lru_count_one() count nr_items lockless to minimize >>>> overhead introduced by locking operation, and to make parallel >>>> reclaims more scalable. >>> >>> And... what were the effects of the patch? Did you not run the same >>> performance tests after applying it? >> >> I've just detected the such high usage of shrink slab on production node. It's rather >> difficult to make it use another kernel, than it uses, only kpatches are possible. >> So, I haven't estimated how it acts on node's performance. >> On test node I see, that the patch obviously removes raw_spin_lock from perf profile. >> So, it's a little bit untested in this way. > > Well that's a problem. The patch increases list_lru.o text size by a > lot (4800->5696) which will have a cost. And we don't have proof that > any benefit is worth that cost. It shouldn't be too hard to cook up a > synthetic test to trigger memcg slab reclaim and then run a > before-n-after benchmark? Ok, then, please, ignore this for a while, I'll try to do it a little bit later. Kirill -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org