From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 75721 invoked by alias); 10 Aug 2016 15:39:57 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 75701 invoked by uid 89); 10 Aug 2016 15:39:56 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 spammy=spinning, H*i:sk:y0m60r8, H*f:sk:y0m60r8, H*MI:sk:y0m60r8 X-HELO: mail-wm0-f41.google.com Received: from mail-wm0-f41.google.com (HELO mail-wm0-f41.google.com) (74.125.82.41) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Wed, 10 Aug 2016 15:39:45 +0000 Received: by mail-wm0-f41.google.com with SMTP id f65so97872388wmi.0 for ; Wed, 10 Aug 2016 08:39:44 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:cc:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-transfer-encoding; bh=ulT3KC3iU+OGOF8HzbaIHdw2XKDSb1ognNshdGFYB/w=; b=cvWryaC9RpZhN6f4BR2VWjqmDS0De8i9CLDdCV7Wt1ic4Gzieb8rNm2JQ7pHqqKOh7 fDATYy8Kt4dhwAMpdc2CQ8/h/c4WIbZhrcnCfm5Lb1ZAXkwngqKa6yb9GsrJcdExB8Cz iLSXAnI7z/CuYvNRJ+mV5jpxS6rqdABhascn5JBqKleRvy7C26UPkb0qzO6IwZt4hWV0 MDfPw8495kpzt1qUlzRbXRl0whjIh86XgfYVAXh1SYLmJndDqB2Cs1LHXTKET8SseWIm YrHqS+cKDobvvV9svtBtvR4+ETtB78sSchvkYDUJerhOACKIDQX4Cgcj755qXdDl70AW e6hg== X-Gm-Message-State: AEkoousrydgB5f6ps+IwQ3tkmBqxqZGR6lXcIKdWao1LB53rB6CfeWkPtX69QEknaP9Bfw== X-Received: by 10.28.169.203 with SMTP id s194mr4025662wme.95.1470843581401; Wed, 10 Aug 2016 08:39:41 -0700 (PDT) Received: from avi.cloudius-systems.com ([37.142.229.250]) by smtp.gmail.com with ESMTPSA id r16sm8936227wme.16.2016.08.10.08.39.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Aug 2016 08:39:40 -0700 (PDT) Subject: Re: Some newbie questions To: "Frank Ch. Eigler" References: <20160809112501.GK2508@stream> <91592a2a-7373-6a27-413c-cf4aca70cb76@scylladb.com> Cc: Mark Wielaard , David Smith , systemtap@sourceware.org From: Avi Kivity Message-ID: <5ff2fd95-ec7a-4d4a-3687-d5d59c4aee7d@scylladb.com> Date: Wed, 10 Aug 2016 15:39:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-q3/txt/msg00153.txt.bz2 On 08/10/2016 06:32 PM, Frank Ch. Eigler wrote: > Avi Kivity writes: > >> [...] >> I'm surprised this didn't come up before. Trying to find out why a >> function which is usually fast and very rarely slow seems to be a good >> fit for systemtap. > Like this? > https://sourceware.org/systemtap/examples/#profiling/fntimes.stp Yes. The problem is that if the function is called often (with a usual short running time), then systemtap will eat all of the cpu time spinning on an internal lock. > Note though that such analysis probably cannot be performed based only > upon PC samples - or even backtrace samples. We seem to require > trapping individual function entry/exit events. That's why I tried systemtap. It worked will on my desktop, but very badly in production.