From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753602AbbBASHH (ORCPT ); Sun, 1 Feb 2015 13:07:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33259 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753480AbbBASHE (ORCPT ); Sun, 1 Feb 2015 13:07:04 -0500 Date: Sun, 1 Feb 2015 19:06:35 +0100 From: Jiri Olsa To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra , LKML , David Ahern , Adrian Hunter , Andi Kleen , Stephane Eranian , Frederic Weisbecker Subject: Re: [PATCH 14/42] perf record: Add --index option for building index table Message-ID: <20150201180635.GA6317@krava.brq.redhat.com> References: <1422518843-25818-1-git-send-email-namhyung@kernel.org> <1422518843-25818-15-git-send-email-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1422518843-25818-15-git-send-email-namhyung@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 29, 2015 at 05:06:55PM +0900, Namhyung Kim wrote: > The new --index option will create indexed data file which can be > processed by multiple threads parallelly. It saves meta event and > sample data in separate files and merges them with an index table. > > To build an index table, it needs to know exact offsets and sizes for > each sample data. However the offset only can be calculated after the > feature data is fixed, and to save feature data it needs to access to > the sample data because it needs to mark used DSOs for build-id table. > > So I ended up with reserving 1MB hole for the feature data area and then > put sample data and calculated offsets. Now an indexed perf data file > will look like below: > > +---------------------+ > | file header | > |---------------------| > | | > | meta events | > | | > |---------------------| > | feature data | > | (contains index) -+--+ > |---------------------| | > | ~1MB hole | | > |---------------------| | > | | | > | sample data[1] <-+--+ > | | | > |---------------------| | > | | | > | sample data[2] <-|--+ > | | | > |---------------------| | > | ... | ... > +---------------------+ I also dont see how to store it in a nice way under current header layout, but how about bump up the header version for this feature? ;-) currently it's: struct perf_file_header { u64 magic; u64 size; u64 attr_size; struct perf_file_section attrs; struct perf_file_section data; /* event_types is ignored */ struct perf_file_section event_types; DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS); }; - we already store attrs as a FEATURE so we could omit that - your patch stores only synthesized data into 'data' section (-1 idx) this could be stored into separate file and get merged with the rest - new header version would have 'features' section, so the features position wouldnt depend on the 'data' end as of now and we could easily store after all data is merged: struct perf_file_header { u64 magic; u64 size; u64 attr_size; struct perf_file_section features; DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS); }; thoughts? jirka