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=-7.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BE175C07E95 for ; Sun, 4 Jul 2021 23:59:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 97DCB6128D for ; Sun, 4 Jul 2021 23:59:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229734AbhGEABl (ORCPT ); Sun, 4 Jul 2021 20:01:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:46492 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229642AbhGEABk (ORCPT ); Sun, 4 Jul 2021 20:01:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1789B613D0; Sun, 4 Jul 2021 23:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625443144; bh=m0kblN6hNdNA8DEWQiP9DvAg6qs/MoaiNtlaCeBXXCU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=girBCqlUzJ1ALojSFoaEjAnpjiM0ZUVo/d+gRBsS0bEJ12FYTjWSKkFhO86ezVtpt IcTkkyWgqcamzUVxDD2F/3gtca6YrudzGwlSxW+1IwR7UtO/l0bSAwXbomrEzeRnsI 8vtbtf1SUrafkWBev4lRqfqLzRP3djC/yuJ5tUHHTcxe0jm05KFjOnQ1M3FnGf2zbi ImLsb6R80aiozlW0qvbbp9yFY2CIgXZQWFNPMfrvycobcJzz1v34W01kYPEuWBvxi3 8JQWxjc3K4JlnbEQUk/Y22CakLGQEpsxgJar0SybPV1q2SYDR8fNcEvE8PCjGF0qgY sPvbmAI+aF5dA== Date: Mon, 5 Jul 2021 08:59:01 +0900 From: Masami Hiramatsu To: Christoph Hellwig Cc: "wuqiang.matt" , naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, davem@davemloft.net, mhiramat@kernel.org, mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, mattwu@163.com Subject: Re: [PATCH] kretprobe scalability improvement Message-Id: <20210705085901.20f97a48c37fdc533d554dc6@kernel.org> In-Reply-To: References: <20210703102818.20766-1-wuqiang.matt@bytedance.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 4 Jul 2021 10:16:47 +0100 Christoph Hellwig wrote: > Would it make sense to just reuse kernel/bpf/percpu_freelist.c for > kretprobes? Hmm, I don't think so. It seems that what Wuqiang proposed is more efficient than the percpu_freelist, and it will be less efficient from the viewpoint of memory usage because kretprobe freelist manages instance pool among all CPUs (which can be unbalanced, sometimes 95% used by one core, sometimes used evenly). Actually, the best solution is to have per-task fixed-size instance pool which is shared by all kretprobes (e.g. 4kb/task), because the instance makes a "shadow stack" for each task. This may consume more memory but is not increased by adding kretprobes, and should be scalable. Thank you, -- Masami Hiramatsu