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=-7.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 557F7C433EF for ; Wed, 22 Sep 2021 08:47:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 319DA60F12 for ; Wed, 22 Sep 2021 08:47:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233996AbhIVIsm (ORCPT ); Wed, 22 Sep 2021 04:48:42 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:48544 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233792AbhIVIsl (ORCPT ); Wed, 22 Sep 2021 04:48:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632300431; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RzE7ct7TcGCXm8mUaKMPJj+IqZtEjSH8Rgo1FH7r3qU=; b=GUIv44KFY15m3ro+OgNSbeL+dJiO2sUGUSy2+OAJ7LfwrsgZYHpKcE2sKtVOD9Q3eqZtwF jeKAz5AkPj924kbNHEhjdSJeIjxw86xKjK5zfpOdu7/9OKa2uZavoLkLbVCsbaNL/eBuZn zvV1GglgG5YlB6T+J+eav9y2bolKGR4= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-428-HFxEIHToPZyX5J659XmYWA-1; Wed, 22 Sep 2021 04:47:10 -0400 X-MC-Unique: HFxEIHToPZyX5J659XmYWA-1 Received: by mail-wr1-f69.google.com with SMTP id i4-20020a5d5224000000b0015b14db14deso1436713wra.23 for ; Wed, 22 Sep 2021 01:47:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=RzE7ct7TcGCXm8mUaKMPJj+IqZtEjSH8Rgo1FH7r3qU=; b=ZD6GSYTTTqyHwnCh5kDCA/n3/V1did+oTcgAWushK2n9irn9q6QMd9gMsP0tkX9fhh oHynV39yDJkT91vAippvBgD+UuCddojM3ECWcsWryiml9QO9NrfJ884eFb246jpUJKq6 jLQLnj7qK9FXa/tlhxGBBMqKXSOL7KWeXLB8sdSbMtcC51CzNJ6OkMCzMe1P/+Sfg1dA 5mK/XI1P9Lc2iqR6xGMUw5M040VlMg352srDbsD3/x0cFLRAPlXT4l+oEFtaHKJLemoa ArfEGIjnEBaOqsXI+h5GGzik6hY2y8fatSXY61+p6r0qBDhdKgR1i9avGwmETRhCjCJG by6Q== X-Gm-Message-State: AOAM533UTVFX7qvO6SABNUHHy9LJxf2vt6BZ+ieHBFpxMu8Vg2UfXQic qoI5EPwiFCFPIDpxiwQeicIaGfpv4QIsQKdSTc9eskz26TtPox4pA9ULvd8rsIgy+t6r+kdgDen yTQdkIdNTVuWZJoqwC+LSJ6oD X-Received: by 2002:a05:600c:206:: with SMTP id 6mr3180747wmi.114.1632300428758; Wed, 22 Sep 2021 01:47:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwWyFTZqMVTFCG4e3JArxU0wOw41T1HqTgwLv6yHZRJpHA8FeYLz93DWE/1ppRavCbpJORW0g== X-Received: by 2002:a05:600c:206:: with SMTP id 6mr3180710wmi.114.1632300428502; Wed, 22 Sep 2021 01:47:08 -0700 (PDT) Received: from ?IPv6:2a0c:5a80:1d03:b900:c3d1:5974:ce92:3123? ([2a0c:5a80:1d03:b900:c3d1:5974:ce92:3123]) by smtp.gmail.com with ESMTPSA id r27sm1464087wrr.70.2021.09.22.01.47.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 01:47:08 -0700 (PDT) Message-ID: <0ec733daf2daaf8a6f5b1fbf56676b9892d5bf73.camel@redhat.com> Subject: Re: [PATCH 2/6] mm/swap: Introduce alternative per-cpu LRU cache locking From: nsaenzju@redhat.com To: Peter Zijlstra Cc: akpm@linux-foundation.org, frederic@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, cl@linux.com, juri.lelli@redhat.com, mingo@redhat.com, mtosatti@redhat.com, nilal@redhat.com, mgorman@suse.de, ppandit@redhat.com, williams@redhat.com, bigeasy@linutronix.de, anna-maria@linutronix.de, linux-rt-users@vger.kernel.org Date: Wed, 22 Sep 2021 10:47:07 +0200 In-Reply-To: <20210921220358.GN4323@worktop.programming.kicks-ass.net> References: <20210921161323.607817-1-nsaenzju@redhat.com> <20210921161323.607817-3-nsaenzju@redhat.com> <20210921220358.GN4323@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.4 (3.40.4-1.fc34) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2021-09-22 at 00:03 +0200, Peter Zijlstra wrote: > On Tue, Sep 21, 2021 at 06:13:20PM +0200, Nicolas Saenz Julienne wrote: > > +static inline void lru_cache_lock(struct lru_cache_locks *locks) > > +{ > > + if (static_branch_unlikely(&remote_pcpu_cache_access)) { > > + /* Avoid migration between this_cpu_ptr() and spin_lock() */ > > + migrate_disable(); > > + spin_lock(this_cpu_ptr(&locks->spin)); > > + } else { > > + local_lock(&locks->local); > > + } > > +} > > > +static inline void lru_cache_unlock(struct lru_cache_locks *locks) > > +{ > > + if (static_branch_unlikely(&remote_pcpu_cache_access)) { > > + spin_unlock(this_cpu_ptr(&locks->spin)); > > + migrate_enable(); > > + } else { > > + local_unlock(&locks->local); > > + } > > +} > > *why* use migrate_disable(), that's horrible! I was trying to be mindful of RT. They don't appreciate people taking spinlocks just after having disabled preemption. I think getting local_lock(&locks->local) is my only option then. But it adds an extra redundant spinlock in the RT+NOHZ_FULL case. -- Nicolás Sáenz 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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 502D6C433FE for ; Wed, 22 Sep 2021 08:47:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB03960F12 for ; Wed, 22 Sep 2021 08:47:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EB03960F12 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 752CE900002; Wed, 22 Sep 2021 04:47:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 702ED6B0072; Wed, 22 Sep 2021 04:47:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5CC8D900002; Wed, 22 Sep 2021 04:47:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0205.hostedemail.com [216.40.44.205]) by kanga.kvack.org (Postfix) with ESMTP id 4FA5E6B006C for ; Wed, 22 Sep 2021 04:47:12 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0911C1824DBC5 for ; Wed, 22 Sep 2021 08:47:11 +0000 (UTC) X-FDA: 78614579904.05.F92B685 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf19.hostedemail.com (Postfix) with ESMTP id 71D21B0000AD for ; Wed, 22 Sep 2021 08:47:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632300430; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RzE7ct7TcGCXm8mUaKMPJj+IqZtEjSH8Rgo1FH7r3qU=; b=Emgn54Jthjg/Hkq5Ur2euNkt8RjDPYM3bJzoKR/r7zhrq9wsaAcC1wMFeQhBZP+JDIThMd epruzFMtH9mCvvyOd7JR0uxXJKbZo++rbC14TFQv6LUIB+ct2KoRlkC5R3tGWpr5/n0Vtk SMGQq1Z2j+Y3htxWuyrV4l6lHG066Ww= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-323-m9qNZz8KNyitdGMIxuspSA-1; Wed, 22 Sep 2021 04:47:09 -0400 X-MC-Unique: m9qNZz8KNyitdGMIxuspSA-1 Received: by mail-wr1-f72.google.com with SMTP id m1-20020a056000180100b0015e1ec30ac3so1482903wrh.8 for ; Wed, 22 Sep 2021 01:47:09 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=RzE7ct7TcGCXm8mUaKMPJj+IqZtEjSH8Rgo1FH7r3qU=; b=ILEXHXS9JWufwldwJ6rx2TdNlOxfFvejlNU5Ci7u7a45ACKnvtZ9G3AZ1RANBoPv9C 5lmf1fxMmZhkKRhsjexyg6kV66vwpWOJjywxPdFeUl1w/weQMYR+FwE58fhAHSQnnili LcU8y0ezhVXUHlfThyAmPiaItixwpUZ9AkY/fN6LBKisyREJb+Ao0J2dpz3D7+JTz/K3 isjumYx4OTBUCVJCaJlwyA1cc31xfw2k/g97KefL0hJxrHMU9Wyukb9A3kWYRNW+DFm+ zK/QjbpRR5O8pFfo7H2ZAZq+J9lc8BBqLTD8pY8mYE6fIM3m8cfmBbCKu/ghN+qa9T2a F4ZA== X-Gm-Message-State: AOAM533Sw+O3WLa5BO+rsoK+yzQSY1ZkhV3mFF6kOJg0yiTSsJPpFt3X S0W9nuSV4j07RfcAJJyGguhahj0dUC+w/rHWo9PElMR1I8Ez4+Wh+qL/PMLGKQQxQ2qEwlCJypd O8YY9LnPkJY8= X-Received: by 2002:a05:600c:206:: with SMTP id 6mr3180744wmi.114.1632300428757; Wed, 22 Sep 2021 01:47:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwWyFTZqMVTFCG4e3JArxU0wOw41T1HqTgwLv6yHZRJpHA8FeYLz93DWE/1ppRavCbpJORW0g== X-Received: by 2002:a05:600c:206:: with SMTP id 6mr3180710wmi.114.1632300428502; Wed, 22 Sep 2021 01:47:08 -0700 (PDT) Received: from ?IPv6:2a0c:5a80:1d03:b900:c3d1:5974:ce92:3123? ([2a0c:5a80:1d03:b900:c3d1:5974:ce92:3123]) by smtp.gmail.com with ESMTPSA id r27sm1464087wrr.70.2021.09.22.01.47.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Sep 2021 01:47:08 -0700 (PDT) Message-ID: <0ec733daf2daaf8a6f5b1fbf56676b9892d5bf73.camel@redhat.com> Subject: Re: [PATCH 2/6] mm/swap: Introduce alternative per-cpu LRU cache locking From: nsaenzju@redhat.com To: Peter Zijlstra Cc: akpm@linux-foundation.org, frederic@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, cl@linux.com, juri.lelli@redhat.com, mingo@redhat.com, mtosatti@redhat.com, nilal@redhat.com, mgorman@suse.de, ppandit@redhat.com, williams@redhat.com, bigeasy@linutronix.de, anna-maria@linutronix.de, linux-rt-users@vger.kernel.org Date: Wed, 22 Sep 2021 10:47:07 +0200 In-Reply-To: <20210921220358.GN4323@worktop.programming.kicks-ass.net> References: <20210921161323.607817-1-nsaenzju@redhat.com> <20210921161323.607817-3-nsaenzju@redhat.com> <20210921220358.GN4323@worktop.programming.kicks-ass.net> User-Agent: Evolution 3.40.4 (3.40.4-1.fc34) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: gwd1kmibshsopra4rud4raqtkepjfcu6 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Emgn54Jt; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf19.hostedemail.com: domain of nsaenzju@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=nsaenzju@redhat.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 71D21B0000AD X-HE-Tag: 1632300431-935599 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.070806, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 2021-09-22 at 00:03 +0200, Peter Zijlstra wrote: > On Tue, Sep 21, 2021 at 06:13:20PM +0200, Nicolas Saenz Julienne wrote: > > +static inline void lru_cache_lock(struct lru_cache_locks *locks) > > +{ > > + if (static_branch_unlikely(&remote_pcpu_cache_access)) { > > + /* Avoid migration between this_cpu_ptr() and spin_lock() */ > > + migrate_disable(); > > + spin_lock(this_cpu_ptr(&locks->spin)); > > + } else { > > + local_lock(&locks->local); > > + } > > +} >=20 > > +static inline void lru_cache_unlock(struct lru_cache_locks *locks) > > +{ > > + if (static_branch_unlikely(&remote_pcpu_cache_access)) { > > + spin_unlock(this_cpu_ptr(&locks->spin)); > > + migrate_enable(); > > + } else { > > + local_unlock(&locks->local); > > + } > > +} >=20 > *why* use migrate_disable(), that's horrible! I was trying to be mindful of RT. They don't appreciate people taking spi= nlocks just after having disabled preemption. I think getting local_lock(&locks->local) is my only option then. But it = adds an extra redundant spinlock in the RT+NOHZ_FULL case. --=20 Nicol=C3=A1s S=C3=A1enz