From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 639ADC47254 for ; Tue, 5 May 2020 16:13:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34B5C206A4 for ; Tue, 5 May 2020 16:13:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="k1HmngUN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730627AbgEEQNp (ORCPT ); Tue, 5 May 2020 12:13:45 -0400 Received: from smtp-fw-9101.amazon.com ([207.171.184.25]:5592 "EHLO smtp-fw-9101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729765AbgEEQNm (ORCPT ); Tue, 5 May 2020 12:13:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1588695222; x=1620231222; h=from:to:cc:subject:date:message-id:in-reply-to: mime-version; bh=KzvE+DVjzy/zrI1y9QhRcUUXKHj3IDMUSCkxhsXLtEM=; b=k1HmngUNjFBQkv/HnRiY35X/2hF2jlysrf67YglREdRs0vRKuGHZKeOg B97YimC78pbA0oSPrXzZn046ox+ze0YnISZG0wDblOvDU2xKT5BhmmB3L xhtKwWoEAP5G2Y3D52L4OPzbcv5MltSQQAqVJltO/J/XcA63Ni2EGe9F7 I=; IronPort-SDR: xjLM36pNFmpanr4FmO5MQR+NRdJl03/cefOtoL7Zf9khbQnmUXqUq526sBI2b1Ohg3vf9AZLE1 3VvwQM1ViZXg== X-IronPort-AV: E=Sophos;i="5.73,355,1583193600"; d="scan'208";a="33080699" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-1e-27fb8269.us-east-1.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-9101.sea19.amazon.com with ESMTP; 05 May 2020 16:13:38 +0000 Received: from EX13MTAUEA002.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan3.iad.amazon.com [10.40.159.166]) by email-inbound-relay-1e-27fb8269.us-east-1.amazon.com (Postfix) with ESMTPS id 5D662A21BE; Tue, 5 May 2020 16:13:35 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 5 May 2020 16:13:34 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.160.26) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 5 May 2020 16:13:25 +0000 From: SeongJae Park To: Eric Dumazet CC: SeongJae Park , Eric Dumazet , David Miller , Al Viro , "Jakub Kicinski" , Greg Kroah-Hartman , , netdev , LKML , SeongJae Park , , , Subject: Re: Re: Re: [PATCH net v2 0/2] Revert the 'socket_alloc' life cycle change Date: Tue, 5 May 2020 18:13:02 +0200 Message-ID: <20200505161302.547-1-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: (raw) MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.43.160.26] X-ClientProxiedBy: EX13D21UWB002.ant.amazon.com (10.43.161.177) To EX13D31EUA001.ant.amazon.com (10.43.165.15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 May 2020 09:00:44 -0700 Eric Dumazet wrote: > On Tue, May 5, 2020 at 8:47 AM SeongJae Park wrote: > > > > On Tue, 5 May 2020 08:20:50 -0700 Eric Dumazet wrote: > > > > > > > > > > > On 5/5/20 8:07 AM, SeongJae Park wrote: > > > > On Tue, 5 May 2020 07:53:39 -0700 Eric Dumazet wrote: > > > > > > > > > > >> Why do we have 10,000,000 objects around ? Could this be because of > > > >> some RCU problem ? > > > > > > > > Mainly because of a long RCU grace period, as you guess. I have no idea how > > > > the grace period became so long in this case. > > > > > > > > As my test machine was a virtual machine instance, I guess RCU readers > > > > preemption[1] like problem might affected this. > > > > > > > > [1] https://www.usenix.org/system/files/conference/atc17/atc17-prasad.pdf > > > > > > > >> > > > >> Once Al patches reverted, do you have 10,000,000 sock_alloc around ? > > > > > > > > Yes, both the old kernel that prior to Al's patches and the recent kernel > > > > reverting the Al's patches didn't reproduce the problem. > > > > > > > > > > I repeat my question : Do you have 10,000,000 (smaller) objects kept in slab caches ? > > > > > > TCP sockets use the (very complex, error prone) SLAB_TYPESAFE_BY_RCU, but not the struct socket_wq > > > object that was allocated in sock_alloc_inode() before Al patches. > > > > > > These objects should be visible in kmalloc-64 kmem cache. > > > > Not exactly the 10,000,000, as it is only the possible highest number, but I > > was able to observe clear exponential increase of the number of the objects > > using slabtop. Before the start of the problematic workload, the number of > > objects of 'kmalloc-64' was 5760, but I was able to observe the number increase > > to 1,136,576. > > > > OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME > > before: 5760 5088 88% 0.06K 90 64 360K kmalloc-64 > > after: 1136576 1136576 100% 0.06K 17759 64 71036K kmalloc-64 > > > > Great, thanks. > > How recent is the kernel you are running for your experiment ? It's based on 5.4.35. > > Let's make sure the bug is not in RCU. One thing I can currently say is that the grace period passes at last. I modified the benchmark to repeat not 10,000 times but only 5,000 times to run the test without OOM but easily observable memory pressure. As soon as the benchmark finishes, the memory were freed. If you need more tests, please let me know. Thanks, SeongJae Park > > After Al changes, RCU got slightly better under stress. >