From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS53758 23.128.96.0/24 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id 5689D1F670 for ; Mon, 11 Oct 2021 16:32:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232322AbhJKQev (ORCPT ); Mon, 11 Oct 2021 12:34:51 -0400 Received: from cloud.peff.net ([104.130.231.41]:37050 "EHLO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232375AbhJKQeu (ORCPT ); Mon, 11 Oct 2021 12:34:50 -0400 Received: (qmail 29193 invoked by uid 109); 11 Oct 2021 16:32:49 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with ESMTP; Mon, 11 Oct 2021 16:32:49 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 19907 invoked by uid 111); 11 Oct 2021 16:32:49 -0000 Received: from coredump.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.2) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Mon, 11 Oct 2021 12:32:49 -0400 Authentication-Results: peff.net; auth=none Date: Mon, 11 Oct 2021 12:32:49 -0400 From: Jeff King To: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason Cc: =?utf-8?B?UmVuw6k=?= Scharfe , Junio C Hamano , Derrick Stolee , Derrick Stolee via GitGitGadget , Git List Subject: Re: "git reflog expire" blindly trusting timestamps in reflogs Message-ID: References: <30df5e39-3f2a-00d8-541b-347c43f36b38@gmail.com> <581663a7-9b16-e464-ada7-368f20c99ff1@web.de> <87wnmmkzaa.fsf@evledraar.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87wnmmkzaa.fsf@evledraar.gmail.com> Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Sat, Oct 09, 2021 at 04:57:20PM +0200, Ævar Arnfjörð Bjarmason wrote: > On Sat, Oct 09 2021, René Scharfe wrote: > > > Turn off automatic background maintenance for perf tests by default to > > avoid interference with performance measurements. > > Turning off background GC during the perf tests seems like a good idea > in general, so I think this patch should go in. Even with the WIP > (haven't picked it up again in a while) test mode I menitoned in[1] it > still wouldn't make any sense to run detached background GC in t/perf. > > Because first of all we take the repo as-is (hardlinks and all), so > changing it is a bug in itself. Lots of perf tests modify the repository. This is generally OK as Git tends to write and rename tempfiles (breaking the hardlink) rather than modifying anything in place. We also only do the hardlink thing for the objects/ directory, so the scope is limited. It does make me a little nervous, but to my knowledge we've never had a perf test which hurt the original donor repo in this way. And there are more subtle ways to screw things up with various filesystem references; see 36e834abc1 (t/perf: avoid copying worktree files from test repo, 2021-02-26). That's all just an aside; I agree that we should avoid background gc just because it confuses performance tests. -Peff