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=-3.5 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 09913C433EF for ; Tue, 21 Sep 2021 22:04:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8A76860F9E for ; Tue, 21 Sep 2021 22:04:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8A76860F9E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 1E9BC6B006C; Tue, 21 Sep 2021 18:04:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 196746B0071; Tue, 21 Sep 2021 18:04:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 00E3A900002; Tue, 21 Sep 2021 18:04:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id E89A96B006C for ; Tue, 21 Sep 2021 18:04:40 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A00638249980 for ; Tue, 21 Sep 2021 22:04:40 +0000 (UTC) X-FDA: 78612960720.03.0BFD6EB Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf18.hostedemail.com (Postfix) with ESMTP id 4CC184002092 for ; Tue, 21 Sep 2021 22:04:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=x/UjHBXWKbw/Bq/O4XA3P2t47w4xKmeiHWunwBQt2FI=; b=bFWwtBro5+TnqlxOVXw1Un4YD7 wWIWFF2Di+S+8FjiQRvOB3x/FUpIpwjO84lkVb6kPN5gmfM6yQDwjTsd9Hdnvev4iHO/p+gn1RBz8 CETK/G3cHnFpiEH3NYdv+Oe5xEGrbrmgAKXz/Hzgwo1ScfHUDfeXkRBspMOLHmaYvHrp358KxpCKA oxB9s8gFzSdQr9ewiOUIFTTnqdCCKBYgCBNIx+TQwOut9BzJvuMVI1Fsh1pyxeeGs15H08P/sbIPK kyF+xuwlVp3C7LB4GV7tBh/Y+jkcIpmLoSKw/hrkXMmFZUXOrxgOdJElf/wyyKtw/gAaURW+u1U2V NLiE4o2w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mSnrr-004Dui-2C; Tue, 21 Sep 2021 22:04:07 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 2471F981483; Wed, 22 Sep 2021 00:03:58 +0200 (CEST) Date: Wed, 22 Sep 2021 00:03:58 +0200 From: Peter Zijlstra To: Nicolas Saenz Julienne 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 Subject: Re: [PATCH 2/6] mm/swap: Introduce alternative per-cpu LRU cache locking Message-ID: <20210921220358.GN4323@worktop.programming.kicks-ass.net> References: <20210921161323.607817-1-nsaenzju@redhat.com> <20210921161323.607817-3-nsaenzju@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210921161323.607817-3-nsaenzju@redhat.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4CC184002092 X-Stat-Signature: 4xf3a4ixi9x4snned8c1b7gk3jfnj7ik Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=bFWwtBro; spf=none (imf18.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none X-HE-Tag: 1632261879-795731 X-Bogosity: Ham, tests=bogofilter, spamicity=0.005310, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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!