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=-4.0 required=3.0 tests=BAYES_00, 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 BF1ABC433DF for ; Tue, 11 Aug 2020 14:40:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7DE62206C3 for ; Tue, 11 Aug 2020 14:40:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728845AbgHKOky (ORCPT ); Tue, 11 Aug 2020 10:40:54 -0400 Received: from mga02.intel.com ([134.134.136.20]:39417 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728750AbgHKOkx (ORCPT ); Tue, 11 Aug 2020 10:40:53 -0400 IronPort-SDR: 53KUnZqTTqY2CHQMgStOOuKS0hr/4CZAP37o6C2N4Jf/1TFRjPv6cksQ94N/KW+8lviwfHpR0X Rdbx6Q9xRtJw== X-IronPort-AV: E=McAfee;i="6000,8403,9710"; a="141595789" X-IronPort-AV: E=Sophos;i="5.76,461,1592895600"; d="scan'208";a="141595789" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Aug 2020 07:40:53 -0700 IronPort-SDR: JGfBK8o+ksaoxfDMs5qMmlA6+A78FyKE42qHn7BbegCwAzsraHtXotUojVRJoqvgefCiLl6opJ NWwTNkEGnCuw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,461,1592895600"; d="scan'208";a="324777032" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.21]) by orsmga008.jf.intel.com with ESMTP; 11 Aug 2020 07:40:53 -0700 Received: by tassilo.localdomain (Postfix, from userid 1000) id C5847301CAF; Tue, 11 Aug 2020 07:29:55 -0700 (PDT) Date: Tue, 11 Aug 2020 07:29:55 -0700 From: Andi Kleen To: Peter Zijlstra Cc: Alexander Shishkin , Arnaldo Carvalho de Melo , Ingo Molnar , linux-kernel@vger.kernel.org, Jiri Olsa , alexey.budankov@linux.intel.com, adrian.hunter@intel.com Subject: Re: [PATCH 1/2] perf: Add closing sibling events' file descriptors Message-ID: <20200811142955.GC1448395@tassilo.jf.intel.com> References: <20200708151635.81239-1-alexander.shishkin@linux.intel.com> <20200708151635.81239-2-alexander.shishkin@linux.intel.com> <20200806083530.GV2674@hirez.programming.kicks-ass.net> <20200806153205.GA1448395@tassilo.jf.intel.com> <875z9q1u3g.fsf@ashishki-desk.ger.corp.intel.com> <20200810144518.GB1448395@tassilo.jf.intel.com> <20200810203632.GF3982@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200810203632.GF3982@worktop.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 10, 2020 at 10:36:32PM +0200, Peter Zijlstra wrote: > On Mon, Aug 10, 2020 at 07:45:18AM -0700, Andi Kleen wrote: > > > Unfortunately we're kind of stuck with the old NFILE=1024 default > > even though it makes little sense on modern servers. > > Why can't that be changed? It seems to me all of userspace changes all > the time; heck that system-doofus thing flushed 20+ years of sysadmin > experience down the drain, just cause. Why can't we up a file limit? We could try, but I believe it's hard coded in various places outside the kernel. But this wouldn't solve the problem of the unnecessary overhead of the inode + file descriptor per event that the patch was trying to address. It would just waste more memory. And increasing it makes the worst case memory consumption you complained about event worse because the real limit per uid i RLIMIT_NPROC*RLIMIT_FILES. Of course NPROC needs to be large enough too, so the total just becomes bigger and bigger. Ultimatively you need another accounting mechanism that actually works per uid without extra factors. Now perf already has one so it's still unclear to me why we can't use it. -Andi