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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1E5BC77B75 for ; Thu, 4 May 2023 03:33:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229649AbjEDDd3 (ORCPT ); Wed, 3 May 2023 23:33:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229711AbjEDDd0 (ORCPT ); Wed, 3 May 2023 23:33:26 -0400 Received: from out-60.mta0.migadu.com (out-60.mta0.migadu.com [IPv6:2001:41d0:1004:224b::3c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7587D19A2 for ; Wed, 3 May 2023 20:33:24 -0700 (PDT) Date: Wed, 3 May 2023 23:33:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1683171200; 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: in-reply-to:in-reply-to:references:references; bh=LHQ0tWOiBXePRONe9lmx+CgLFkYWwKAc8GKV4/q6DkU=; b=l06qAFauAqEclo8mUnMY1YCLzbbmHnEvV+EY2YNo/5E9metuAhrBTLBNyKmDyPjBL96oXJ Sq2/N2krXfhJsoBkaVuwKvWwKl+Fg7w6P6TtEkseIUokAAnEnnzKptcyVqwX1hev7IGajp 4Qgb4H7pO+N54e9Aq5/qIaonS9LZ9yQ= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Kent Overstreet To: Tejun Heo Cc: Suren Baghdasaryan , Johannes Weiner , Michal Hocko , akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, ldufour@linux.ibm.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, keescook@chromium.org, ndesaulniers@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko Subject: Re: [PATCH 00/40] Memory allocation profiling Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, May 03, 2023 at 04:25:30PM -1000, Tejun Heo wrote: > I see. I'm a bit skeptical about the performance angle given that the hot > path can be probably made really cheap even with lookups. In most cases, > it's just gonna be an extra pointer deref and a few more arithmetics. That > can show up in microbenchmarks but it's not gonna be much. The benefit of > going that route would be the tracking thing being mostly self contained. The only way to do it with a single additional pointer deref would be with a completely statically sized hash table without chaining - it'd have to be open addressing. More realistically you're looking at ~3 dependent loads.