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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 10919C54FCC for ; Tue, 21 Apr 2020 15:59:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7E5A2068F for ; Tue, 21 Apr 2020 15:59:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Ng57rUj1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726688AbgDUP7u (ORCPT ); Tue, 21 Apr 2020 11:59:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726012AbgDUP7t (ORCPT ); Tue, 21 Apr 2020 11:59:49 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 86744C061A10; Tue, 21 Apr 2020 08:59:49 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id j4so14981545qkc.11; Tue, 21 Apr 2020 08:59:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=2LEPhwH4RpFN5v0e1kCmLkv3DzSN/+rHxkSDgf5nqLw=; b=Ng57rUj1VZE7/HCPDAIa5xhqfMdqGUuCXcW6j800BSNrl86b53MK2rH2vy0Z615Ta3 RVL10KalY/a97OIa/1geTiRpfnLg57YwERVdFp8gsKfQ78G9HUClg+OU9pm3IEwps8S0 OabqcNU3BdMwll6pQ2FFZLuKjAv4srai6LjiSqx8vZjNMdbfjLxR3qnKontYFAm+oOfQ DEoeeBQR99kpIcnUOwEOki3hZmnShN57OH8yblbINcLB5xkt9szKHbo0cy0wxHzVC/UO ks3RSJOHHBWxojKhEUrucN9W/vBWb9mDsKHYwQmidV22GM6s2nsU0PKJUBKqqgs1VmNW /J9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=2LEPhwH4RpFN5v0e1kCmLkv3DzSN/+rHxkSDgf5nqLw=; b=drfIhmXJKMTXrbiw8/ZtKuvfXg/JXIs2pNelLQSwe7QkerQ/INDeCmP904ciKOHJOw qFC+6fLJmTNIP9itnC3vJczFeLl+tC0k5YDID4UJ30osum1mAfixkDmcd+LEgS2FYGWS fwcT+XDw8I5xy0R+p1h5Kiz6JJVWgdhu8iNZbSjOc2e649hfjkiOqTxg371IcVmRYPAr /B8wjscCGs8Jdg6K7qBkP+MMCB5xlytWNZphxKPe6Mbws9esVEOXLD0iSTC/6vu2hRir zEeSoZZmITO/66MshAmFF6LGDheTU2qtrYyJtbOXTH4FmmgiwhORH351hCRYnhCOlfKI N8xA== X-Gm-Message-State: AGi0PuZXAwFPAe5EGRr5TUBT0e+QgYE70dY4HlbsSEvNtrtXttMWf5st TYDqrjtFYG/YWcI5RdxRJMSJLfVJiI8= X-Google-Smtp-Source: APiQypI7qF6GjgRP0edDXyvLh6CXuaqvcdd7B7e+Z+bDFQpVc9NbLrA8ouNCC42mHoF8YSpphfKs2Q== X-Received: by 2002:a05:620a:252:: with SMTP id q18mr22487211qkn.184.1587484788691; Tue, 21 Apr 2020 08:59:48 -0700 (PDT) Received: from quaco.ghostprotocols.net ([179.97.37.151]) by smtp.gmail.com with ESMTPSA id i5sm1977969qki.42.2020.04.21.08.59.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2020 08:59:48 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 35697409A3; Tue, 21 Apr 2020 12:59:46 -0300 (-03) Date: Tue, 21 Apr 2020 12:59:46 -0300 To: Thomas Richter Cc: "linux-perf-use." , Linux Kernel Mailing List , Heiko Carstens , Sumanth Korikkar , Vasily Gorbik Subject: Re: kernel/perf: Sample data being lost Message-ID: <20200421155946.GB12295@kernel.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Tue, Apr 21, 2020 at 05:54:29PM +0200, Thomas Richter escreveu: > Since a couple of days I see this warning popping up very often: > > [root@m35lp76 perf]# ./perf record --call-graph dwarf -e rb0000 -- find / > [ perf record: Woken up 282 times to write data ] > Warning: > Processed 16999 events and lost 382 chunks! > > Check IO/CPU overload! > > [ perf record: Captured and wrote 125.730 MB perf.data (16219 samples) ] > [root@m35lp76 perf]# > > The machine is idle, its my development system, so not much going on. > It also happens using a software event, for example cycles. It shows > up more often, the larger the sample size is. So for example: > > [root@m35lp76 perf]# pwd > /root/linux/tools/perf > [root@m35lp76 perf]# ./perf record --call-graph dwarf -- find > [ perf record: Woken up 2 times to write data ] > Warning: > Processed 231 events and lost 7 chunks! > > Check IO/CPU overload! > > [ perf record: Captured and wrote 1.000 MB perf.data (130 samples) ] > [root@m35lp76 perf]# > > I have very seldom observed this before, only in extremely rare cases with > a heavily loaded machine. I am wondering what has changed, I haven't > changed anything in the s390 PMU device drivers. > It could be > - common kernel code when writing into the ringbuffer. > - the perf tool too slow to read data from the mapped buffer. > However I have not come across changes in this area. > > Has anybody observed similar issue? > > PS: I have added some printk messages into my PMU devices drivers. > I have seen messages that the 16384 pages for auxilary buffers are full > and that samples have been dropped. Can you try to bisect tools/perf? Something like: git checkout v5.4 build it, no problems? Use it as the 'git bisect good' starting point. - Arnaldo