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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 63441C433E0 for ; Mon, 1 Feb 2021 20:43:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D2D564EBB for ; Mon, 1 Feb 2021 20:43:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230091AbhBAUm6 (ORCPT ); Mon, 1 Feb 2021 15:42:58 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:50732 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229996AbhBAUmx (ORCPT ); Mon, 1 Feb 2021 15:42:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612212087; 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=hEjF4TKFnm4lV3YUmwdjvjrXpcy0me2k51/JJmJIzXs=; b=D21TKFe1lKehneeLMqnyUHUWfSUhresWv9bw1qUZJ34z7E+Y1Hgi1v3Q4LWwGenY0b2pBL 7sbcKBLYQLc2YHwGdgdaFaJebwuAa6a0jmY9JEld70HYrrP5oZWQgAv2K8UtuMVNXSLdtc D5Vl4oS2BLJATHMrHLOe0338kQoSgPA= 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-404-jlOgHGadOtCvm7w4oiOiQA-1; Mon, 01 Feb 2021 15:41:23 -0500 X-MC-Unique: jlOgHGadOtCvm7w4oiOiQA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 41A0D1075647; Mon, 1 Feb 2021 20:41:21 +0000 (UTC) Received: from krava (unknown [10.40.192.169]) by smtp.corp.redhat.com (Postfix) with SMTP id DCAFC60C05; Mon, 1 Feb 2021 20:41:18 +0000 (UTC) Date: Mon, 1 Feb 2021 21:41:17 +0100 From: Jiri Olsa To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra , Mark Rutland , Alexander Shishkin , LKML , Stephane Eranian , Andi Kleen , Ian Rogers Subject: Re: [PATCH 1/3] perf tools: Use /proc//task//status for synthesis Message-ID: References: <20210129054901.1705483-1-namhyung@kernel.org> <20210129054901.1705483-2-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 01, 2021 at 01:41:13PM +0900, Namhyung Kim wrote: > On Mon, Feb 1, 2021 at 8:00 AM Jiri Olsa wrote: > > > > On Fri, Jan 29, 2021 at 02:48:59PM +0900, Namhyung Kim wrote: > > > To save memory usage, it needs to reduce number of entries in the proc > > > filesystem. It's using /proc//task directory to traverse threads > > > in the process and then kernel creates /proc//task/ entries. > > > > > > After that it checks the thread info using the /proc//status file > > > rather than /proc//task//status. As far as I can see, they > > > are the same and contain all the info we need. > > > > > > Using the latter eliminates the unnecessary /proc/ entry. This > > > can be useful especially a large number of threads are used in the > > > system. In my experiment around 1KB of memory on average was saved > > > for each thread (which is not a thread group leader). > > > > > > To do this, pass both pid and tid to perf_event_prepare_comm() if it > > > knows them. In case it doesn't know, passing 0 as pid will do the old > > > way. > > > > > > Signed-off-by: Namhyung Kim > > > --- > > > tools/perf/util/synthetic-events.c | 30 +++++++++++++++++++----------- > > > 1 file changed, 19 insertions(+), 11 deletions(-) > > > > > > diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c > > > index 3a898520f05c..800522591dde 100644 > > > --- a/tools/perf/util/synthetic-events.c > > > +++ b/tools/perf/util/synthetic-events.c > > > @@ -69,7 +69,7 @@ int perf_tool__process_synth_event(struct perf_tool *tool, > > > * Assumes that the first 4095 bytes of /proc/pid/stat contains > > > * the comm, tgid and ppid. > > > */ > > > -static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len, > > > +static int perf_event__get_comm_ids(pid_t pid, pid_t tid, char *comm, size_t len, > > > pid_t *tgid, pid_t *ppid) > > > { > > > char bf[4096]; > > > @@ -81,7 +81,10 @@ static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len, > > > *tgid = -1; > > > *ppid = -1; > > > > > > - snprintf(bf, sizeof(bf), "/proc/%d/status", pid); > > > + if (pid) > > > + snprintf(bf, sizeof(bf), "/proc/%d/task/%d/status", pid, tid); > > > + else > > > + snprintf(bf, sizeof(bf), "/proc/%d/status", tid); > > > > > > fd = open(bf, O_RDONLY); > > > if (fd < 0) { > > > @@ -93,7 +96,7 @@ static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len, > > > close(fd); > > > if (n <= 0) { > > > pr_warning("Couldn't get COMM, tigd and ppid for pid %d\n", > > > - pid); > > > + tid); > > > return -1; > > > } > > > bf[n] = '\0'; > > > @@ -116,27 +119,32 @@ static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len, > > > memcpy(comm, name, size); > > > comm[size] = '\0'; > > > } else { > > > - pr_debug("Name: string not found for pid %d\n", pid); > > > + pr_debug("Name: string not found for pid %d\n", tid); > > > } > > > > > > if (tgids) { > > > tgids += 5; /* strlen("Tgid:") */ > > > *tgid = atoi(tgids); > > > + > > > + if (pid && pid != *tgid) { > > > + pr_debug("Tgid: not match to given pid: %d vs %d\n", > > > + pid, *tgid); > > > > hm, could this actually happen in our case? > > Probably not. I'll remove it in the next version if you want. IMO if there's no reason let's remove it jirka