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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A045EC07E9D for ; Tue, 27 Sep 2022 18:37:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230494AbiI0ShZ (ORCPT ); Tue, 27 Sep 2022 14:37:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40444 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230024AbiI0ShY (ORCPT ); Tue, 27 Sep 2022 14:37:24 -0400 Received: from siwi.pair.com (siwi.pair.com [209.68.5.199]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 489BD1BEA56 for ; Tue, 27 Sep 2022 11:37:21 -0700 (PDT) Received: from siwi.pair.com (localhost [127.0.0.1]) by siwi.pair.com (Postfix) with ESMTP id 69935CA124E; Tue, 27 Sep 2022 14:37:20 -0400 (EDT) Received: from jeffhost-mbp.local (162-238-212-202.lightspeed.rlghnc.sbcglobal.net [162.238.212.202]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by siwi.pair.com (Postfix) with ESMTPSA id 23BFACC832A; Tue, 27 Sep 2022 14:37:20 -0400 (EDT) Subject: Re: [PATCH] pack-bitmap: remove trace2 region from hot path To: Derrick Stolee via GitGitGadget , git@vger.kernel.org Cc: gitster@pobox.com, me@ttaylorr.com, chakrabortyabhradeep79@gmail.com, Derrick Stolee References: From: Jeff Hostetler Message-ID: <4c4954d8-82ea-8674-542e-865c514a7ae5@jeffhostetler.com> Date: Tue, 27 Sep 2022 14:37:19 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: mailmunge 3.09 on 209.68.5.199 Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 9/23/22 9:00 AM, Derrick Stolee via GitGitGadget wrote: > From: Derrick Stolee > > The trace2 region around the call to lazy_bitmap_for_commit() in > bitmap_for_commit() was added in 28cd730680d (pack-bitmap: prepare to > read lookup table extension, 2022-08-14). While adding trace2 regions is > typically helpful for tracking performance, this method is called > possibly thousands of times as a commit walk explores commit history > looking for a matching bitmap. When trace2 output is enabled, this > region is emitted many times and performance is throttled by that > output. > > For now, remove these regions entirely. > > This is a critical path, and it would be valuable to measure that the > time spent in bitmap_for_commit() does not increase when using the > commit lookup table. The best way to do that would be to use a mechanism > that sums the time spent in a region and reports a single value at the > end of the process. This technique was introduced but not merged by [1] > so maybe this example presents some justification to revisit that > approach. > > [1] https://lore.kernel.org/git/pull.1099.v2.git.1640720202.gitgitgadget@gmail.com/ I'll dust off my "timers and counters" series, address the various issues that were raised back in December, and resubmit. Thanks for the reminder. Jeff