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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 F30FBC43387 for ; Mon, 14 Jan 2019 11:03:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C53E820659 for ; Mon, 14 Jan 2019 11:03:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726595AbfANLD2 (ORCPT ); Mon, 14 Jan 2019 06:03:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53736 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726471AbfANLD1 (ORCPT ); Mon, 14 Jan 2019 06:03:27 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6F403C070E1E; Mon, 14 Jan 2019 11:03:27 +0000 (UTC) Received: from krava (unknown [10.43.17.222]) by smtp.corp.redhat.com (Postfix) with SMTP id C0C9419C7C; Mon, 14 Jan 2019 11:03:25 +0000 (UTC) Date: Mon, 14 Jan 2019 12:03:25 +0100 From: Jiri Olsa To: Alexey Budankov Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra , Namhyung Kim , Alexander Shishkin , Andi Kleen , linux-kernel Subject: Re: [PATCH v1 0/4] perf: enable compression of record mode trace to save storage space Message-ID: <20190114110325.GB22336@krava> References: <20190109172843.GE19455@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 14 Jan 2019 11:03:27 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 14, 2019 at 11:43:31AM +0300, Alexey Budankov wrote: > Hi, > On 09.01.2019 20:28, Jiri Olsa wrote: > > On Mon, Dec 24, 2018 at 04:21:33PM +0300, Alexey Budankov wrote: > >> > >> The patch set implements runtime record trace compression accompanied by > >> trace file decompression implemented in the tool report mode. Zstandard > >> library API [1] is used for compression/decompression of data that come > >> from perf_events kernel data buffers. > >> > >> Realized -z,--compression_level=n option provides ~3-5x avg. trace file > >> size reduction on the tested workloads what significantly saves user's > >> storage space on larger server systems where trace file size can easily > >> reach several tens or even hundreds of GiBs, especially when profiling > >> with stacks for later dwarf unwinding, context-switches tracing and etc. > >> > >> The option is effective jointly with asynchronous trace writing because > >> compression requires auxiliary memory buffers to operate on and memory > >> buffers for asynchronous trace writing serve that purpose. > > > > I dont like that it's onlt for aio only, I can't really see why it's > > For serial streaming, on CPU bound codes, under full system utilization it > can induce more runtime overhead and increase data loss because amount of > code on performance critical path grows, of course size of written data > reduces but still. Feeding kernel buffer content by user space code to a > syscall is extended with intermediate copying to user space memory with > doing some math on it in the middle. > > > a problem for normal data.. can't we just have one layer before and > > stream the data to the compress function instead of the file (or aio > > buffers).. and that compress functions would spit out 64K size COMPRESSED > > events, which would go to file (or aio buffers) > > It is already almost like that. Compression could be bridged using AIO > buffers but then still streamed to file serially using record__pushfn() > and that would make some sense for moderate profiling cases on systems > without AIO support and trace streaming based on it. > > > > > the report side would process them (decompress) on the session layer > > before the tool callbacks are called > > It is already pretty similar to that. hum, AFAICS you do that in report code not in on the session layer jirka