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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 8B799C43461 for ; Mon, 14 Sep 2020 19:56:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2FEF2208DB for ; Mon, 14 Sep 2020 19:56:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PBA0EzpQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726023AbgINT4Y (ORCPT ); Mon, 14 Sep 2020 15:56:24 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:55639 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725961AbgINT4W (ORCPT ); Mon, 14 Sep 2020 15:56:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600113380; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oj64U75YwzOzBWW1vmtAEB8kLkj0GhlaalWDVZN2Rao=; b=PBA0EzpQjLaljzq9p2waNjpJV24Be0n+an+nYt9NabF332a45Pd6Fp8kNDinKP4b85YQ18 nIGuV0fkDHSc5VQVzXVXoa0DkM3scqiIPFKbaakhJ1y1zLpIZwbGVvPf/HW1r+929wxQ3j CvgWi8EwwmTAmrHv2vIVh1aw53ZZp6Y= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-242-NiFzDCDJNxWiA0qeqPDEMQ-1; Mon, 14 Sep 2020 15:56:16 -0400 X-MC-Unique: NiFzDCDJNxWiA0qeqPDEMQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AE6341084C8B; Mon, 14 Sep 2020 19:56:14 +0000 (UTC) Received: from krava (unknown [10.40.192.180]) by smtp.corp.redhat.com (Postfix) with SMTP id 3108A5DAA6; Mon, 14 Sep 2020 19:56:05 +0000 (UTC) Date: Mon, 14 Sep 2020 21:56:04 +0200 From: Jiri Olsa To: Stephane Eranian Cc: Peter Zijlstra , Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Mark Rutland , Namhyung Kim , Alexander Shishkin , Michael Petlan , Song Liu , "Frank Ch. Eigler" , Ian Rogers , Alexey Budankov , Andi Kleen , Adrian Hunter Subject: Re: [PATCH 02/26] perf: Introduce mmap3 version of mmap event Message-ID: <20200914195604.GR1714160@krava> References: <20200913210313.1985612-1-jolsa@kernel.org> <20200913210313.1985612-3-jolsa@kernel.org> <20200914090811.GM1362448@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 14, 2020 at 10:26:05AM -0700, Stephane Eranian wrote: > On Mon, Sep 14, 2020 at 2:08 AM wrote: > > > > On Sun, Sep 13, 2020 at 11:41:00PM -0700, Stephane Eranian wrote: > > > On Sun, Sep 13, 2020 at 2:03 PM Jiri Olsa wrote: > > > what happens if I set mmap3 and mmap2? > > > > > > I think using mmap3 for every mmap may be overkill as you add useless > > > 20 bytes to an mmap record. > > > I am not sure if your code handles the case where mmap3 is not needed > > > because there is no buildid, e.g, anonymous memory. > > > It seems to me you've written the patch in such a way that if the user > > > tool supports mmap3, then it supersedes mmap2, and thus > > > you need all the fields of mmap2. But if could be more interesting to > > > return either MMAP2 or MMAP3 depending on tool support > > > and type of mmap, that would certainly save 20 bytes on any anon mmap. > > > But maybe that logic is already in your patch and I missed it. > > > > That, and what if you don't want any of that buildid nonsense at all? I > > always kill that because it makes perf pointlessly slow and has > > absolutely no upsides for me. > > > I have seen situations where the perf tool takes a visibly significant > amount of time (many seconds) to inject the buildids at the end of the > collection > of perf record (same if using perf inject -b). That is because it > needs to go through all the records in the perf.data to find MMAP > records and then read > the buildids from the filesystem. This has caused some problems in our > environment. Having the kernel add the buildid to *relevant* mmaps > would avoid > a lot of that penalty, by avoiding having to parse the perf.data file > and leveraging the fact that the buildid may be in memory already. > Although my concern on > this has to do with large pages and the impact they have on alignment > of sections in memory. I think Ian can comment better on this. > > I think this patch series is useful if it can demonstrate a speedup > during recording (perf record or perf record | perf inject -b). But it I haven't meassured, but I assume skipping of perf.data search at the end of the record will make up for reading buildid for each mmap event.. migt be tricky in mmap events heavy workloads > needs to be > optimized to minimize the volume of useless info returned. And Jiri > needs to decide if MMAP3 is a replacement of MMAP2, or a different > kind of record > targeted at ELF images only in which case some of the fields may be > removed. My tendency would be to go for the latter. yes, I like the latter as well, let's see thanks, jirka