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[77.251.215.224]) by smtp.gmail.com with ESMTPSA id t13sm4164536wra.81.2019.05.24.04.17.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 24 May 2019 04:17:07 -0700 (PDT) From: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason To: SZEDER =?utf-8?Q?G=C3=A1bor?= Cc: Jeff King , Derrick Stolee , Junio C Hamano , Eric Wong , git@vger.kernel.org Subject: Re: [PATCH v3] repack: enable bitmaps by default on bare repos References: <20190313145417.GA24101@sigill.intra.peff.net> <20190314091254.nescpfp3n6mbjpmh@dcvr> <87zhoz8b9o.fsf@evledraar.gmail.com> <20190410225721.GA32262@sigill.intra.peff.net> <20190523113031.GA17448@sigill.intra.peff.net> <87tvdlt1jp.fsf@evledraar.gmail.com> <20190524072724.GH25694@sigill.intra.peff.net> <87r28offs6.fsf@evledraar.gmail.com> <20190524082605.GB9082@sigill.intra.peff.net> <87pno8fcp8.fsf@evledraar.gmail.com> <20190524092920.GD951@szeder.dev> User-agent: Debian GNU/Linux 10 (buster); Emacs 26.1; mu4e 1.1.0 In-reply-to: <20190524092920.GD951@szeder.dev> Date: Fri, 24 May 2019 13:17:06 +0200 Message-ID: <87imu0f6fh.fsf@evledraar.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, May 24 2019, SZEDER G=C3=A1bor wrote: > On Fri, May 24, 2019 at 11:01:39AM +0200, =C3=86var Arnfj=C3=B6r=C3=B0 Bj= armason wrote: >> I don't think it's a performance problem to have an old commit-graph >> lying around. But if you turn on the commit-graph, run gc a bunch, then >> turn it off in config we'll have it lying around forever, even if you do >> subsequent gc's. >> >> So I think we should delete such things on the general principle that >> the end-state of a gc's shouldn't be the accumulation of the values of >> past configuration options if we can help it. >> >> Maybe that screws over other users who did a "commit-graph write" >> without setting gc.writeCommitGraph, but I think the only sane thing to >> do is to make "gc" fully 'own' such things if its turned on at all. > > Note that there is 'core.commitGraph' as well; as long as it's > enabled, no commit-graph files should be deleted. Why? If we won't update it or write it if it's not there, why keep it around? It means the commit-graph code and anything else (like bitmaps) needs to deal with stale data for the common and default gc --auto case. You also can't have e.g. a global core.commitGraph=3Dtrue config along with a per-repo gc.writeCommitGraph=3Dtrue config do what you expect. Now just because you wanted to write it for some you'll end up keeping it around forever because you'd also want to optimistically always use it if it's there. Note that I'm talking about the *default* gc semantics, they don't have to cover all advanced use-cases, just be good enough for most, and it's also important that they're as simple as possible, and don't result in stuff like "my performance sucks because I turned this config option on once a year ago for 2 days".