From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8028 invoked by alias); 22 May 2012 17:53:55 -0000 Received: (qmail 8018 invoked by uid 22791); 22 May 2012 17:53:53 -0000 X-SWARE-Spam-Status: No, hits=-3.2 required=5.0 tests=AWL,BAYES_50,KHOP_RCVD_UNTRUST,KHOP_THREADED,LOTS_OF_MONEY,RCVD_IN_HOSTKARMA_W,RCVD_IN_HOSTKARMA_WL,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from bear.ext.ti.com (HELO bear.ext.ti.com) (192.94.94.41) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 22 May 2012 17:53:40 +0000 Received: from dlelxv30.itg.ti.com ([172.17.2.17]) by bear.ext.ti.com (8.13.7/8.13.7) with ESMTP id q4MHrc8m011784; Tue, 22 May 2012 12:53:38 -0500 Received: from DNCE70.ent.ti.com (dnce70.ent.ti.com [137.167.131.19]) by dlelxv30.itg.ti.com (8.13.8/8.13.8) with ESMTP id q4MHrcur002912; Tue, 22 May 2012 12:53:38 -0500 Received: from DNCE04.ent.ti.com ([fe80::1df0:dc7c:d06:77a3]) by DNCE70.ent.ti.com ([fe80::70c9:b447:24a2:dddc%30]) with mapi id 14.01.0323.003; Tue, 22 May 2012 19:53:37 +0200 From: "Turgis, Frederic" To: "Turgis, Frederic" , "Frank Ch. Eigler" CC: Josh Stone , Mark Wielaard , "systemtap@sourceware.org" Subject: RE: Tune reader_thread poll timeout value Date: Tue, 22 May 2012 17:53:00 -0000 Message-ID: <28BE1A38672C8B4481BB423D0FD1F22E18F6680C@DNCE04.ent.ti.com> References: <28BE1A38672C8B4481BB423D0FD1F22E18F55BE1@DNCE04.ent.ti.com> <1335948371.24235.2.camel@springer.wildebeest.org> <28BE1A38672C8B4481BB423D0FD1F22E18F563C1@DNCE04.ent.ti.com> <4FA19BDD.60605@redhat.com> <28BE1A38672C8B4481BB423D0FD1F22E18F566F9@DNCE04.ent.ti.com> <28BE1A38672C8B4481BB423D0FD1F22E18F5931D@DNCE04.ent.ti.com> <20120507135629.GA4860@redhat.com> <28BE1A38672C8B4481BB423D0FD1F22E18F597A4@DNCE04.ent.ti.com> <28BE1A38672C8B4481BB423D0FD1F22E18F601D8@DNCE04.ent.ti.com> <28BE1A38672C8B4481BB423D0FD1F22E18F60C09@DNCE04.ent.ti.com> In-Reply-To: <28BE1A38672C8B4481BB423D0FD1F22E18F60C09@DNCE04.ent.ti.com> x-exclaimer-md-config: f9c360f5-3d1e-4c3c-8703-f45bf52eff6b Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-IsSubscribed: yes 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 X-SW-Source: 2012-q2/txt/msg00170.txt.bz2 >I'm missing something. Why does the second item not moot the first? >IOW, if we poll with a 5s timeout, why wouldn't the timer.s(1) reports >wake up the ppoll() to avoid waiting till 5s? > > >[FT] >ppoll() wakes-up only when 1 buffer is full. timer.s(1) wakes-up whatever = kernel thread (by the way, I >should check that with contextswitch trace) but trace throughput is very l= ow. After 5 seconds, ppoll >time-outs and the 5 traces done by timer.s(1) at every second are dumped. > >When I say "do not use", it is really for interactivity with terminal. Peo= ple may want to get some >small metric every s, but 5 metrics will be displayed every 5s. Of course,= for a log read later, you >don't care. > >So, yes, people should be cautious with this but well, this is for embedde= d platforms and this is >really our goal. Does it make sense then ? In case of low throughput use cases, we have been= for a long time dumping buffers only every few s isntead of 200us at the c= ost of printing latency. Rare cases but needed. Regards Fred Texas Instruments France SA, 821 Avenue Jack Kilby, 06270 Villeneuve Loubet= . 036 420 040 R.C.S Antibes. Capital de EUR 753.920