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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 34613C433DB for ; Wed, 3 Mar 2021 19:24:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3458264EBB for ; Wed, 3 Mar 2021 19:24:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3458264EBB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gentwo.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8E7636B0005; Wed, 3 Mar 2021 14:24:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 897E96B0006; Wed, 3 Mar 2021 14:24:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 710836B0007; Wed, 3 Mar 2021 14:24:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0106.hostedemail.com [216.40.44.106]) by kanga.kvack.org (Postfix) with ESMTP id 5692B6B0005 for ; Wed, 3 Mar 2021 14:24:04 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 0454C8249980 for ; Wed, 3 Mar 2021 19:24:04 +0000 (UTC) X-FDA: 77879538408.14.B71D447 Received: from gentwo.de (vmi485042.contaboserver.net [161.97.139.209]) by imf17.hostedemail.com (Postfix) with ESMTP id F0A0040F8C1D for ; Wed, 3 Mar 2021 19:23:56 +0000 (UTC) Received: by gentwo.de (Postfix, from userid 1001) id 5B7F3B007D1; Wed, 3 Mar 2021 20:15:58 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by gentwo.de (Postfix) with ESMTP id 59AE2B005D8; Wed, 3 Mar 2021 20:15:58 +0100 (CET) Date: Wed, 3 Mar 2021 20:15:58 +0100 (CET) From: Christoph Lameter To: Matthew Wilcox cc: Xunlei Pang , Vlastimil Babka , Wen Yang , Roman Gushchin , Pekka Enberg , Konstantin Khlebnikov , David Rientjes , linux-kernel@vger.kernel.org, "linux-mm@kvack.org" Subject: Re: [PATCH v2 3/3] mm/slub: Use percpu partial free counter In-Reply-To: <20210303142612.GC2723601@casper.infradead.org> Message-ID: References: <1597061872-58724-1-git-send-email-xlpang@linux.alibaba.com> <1597061872-58724-4-git-send-email-xlpang@linux.alibaba.com> <20210303142612.GC2723601@casper.infradead.org> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Stat-Signature: 5bfwpunq3gkqz3x1ho91se3p56kisdzn X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F0A0040F8C1D Received-SPF: none (gentwo.de>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=gentwo.de; client-ip=161.97.139.209 X-HE-DKIM-Result: none/none X-HE-Tag: 1614799436-688280 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 3 Mar 2021, Matthew Wilcox wrote: > On Tue, Mar 02, 2021 at 10:14:53AM +0100, Christoph Lameter wrote: > > On Mon, 10 Aug 2020, Xunlei Pang wrote: > > > - atomic_long_t partial_free_objs; > > > + atomic_long_t __percpu *partial_free_objs; > > > > A percpu counter is never atomic. Just use unsigned long and use this_cpu > > operations for this thing. That should cut down further on the overhead. > > What about allocations from interrupt context? Should this be a local_t > instead? Can this be allocated in an interrupt context? And I am not sure how local_t relates to that? Percpu counters can be used in an interrupt context without the overhead of the address calculations that are required by a local_t.