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Fri, 19 Jun 2026 08:33:48 -0700 (PDT) Received: from [192.168.1.109] ([136.61.86.144]) by smtp.gmail.com with ESMTPSA id af79cd13be357-920a1819fa5sm271440985a.20.2026.06.19.08.33.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Jun 2026 08:33:47 -0700 (PDT) Message-ID: <7afdaf77-07f5-4d48-955d-e153d148f647@gmail.com> Date: Fri, 19 Jun 2026 11:33:47 -0400 Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] pack-objects: support reachability bitmaps with `--path-walk` To: Taylor Blau Cc: git@vger.kernel.org, Junio C Hamano , Jeff King , Elijah Newren References: <849c659f-efa8-430a-bfac-0c26a3ed1aaa@gmail.com> <131d7ad3-7791-4d6f-bdf3-afa6b0831a71@gmail.com> Content-Language: en-US From: Derrick Stolee In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/19/2026 10:52 AM, Taylor Blau wrote: > On Fri, Jun 19, 2026 at 10:40:51AM -0400, Derrick Stolee wrote: >>> [...] >>> , which gives us: >>> >>> Test HEAD^ HEAD >>> ---------------------------------------------------------------------------------------- >>> 5311.3: size of bitmapped pack 278.8M 278.8M -0.0% >>> 5311.38: size of bitmapped pack (--path-walk) 278.7M 278.7M +0.0% >>> >>> (eliding other tests). I considered whether there are other interesting >>> tests, but I think "repack" is the right layer to run perf tests, since >>> you're always writing a closed pack. We could try different subsets of >>> the repository's objects (which would also have to be closed), but I >>> don't think this is that interesting. >> >> This sort of thing does help to show that we're getting different >> behavior when repacking with and without --path-walk. And this test >> is showing the slightest change for git.git, but is likely more >> impactful for the other repos I've used to demonstrate the benefits. >> >> So this is the kind of data I'm hoping to see, but also with data >> from other repos whose data shapes benefit from --path-walk more >> than git.git and repos where name-hash v1 is sufficient to give a >> similar result. > > I'm glad this is the sort of data you're looking for. I'm happy to run > this on other repositories. > >> I'd also like to see if the repack _time_ changes with this, but >> these direct size comparisons are the biggest indicator I'd like to >> see. > > Unfortunately a timing comparison is kind of a pain here. We'd have to > use test_perf, which will perform the same repack multiple times. We > could do that, though it's wasteful, and changes like bf4a60874af > (p5326: generate pack bitmaps before writing the MIDX bitmap, > 2021-09-17) move us in the opposite direction. > > I'm not opposed to changing this to test_perf if you feel strongly about > it. Repacking is expensive and time-consuming. I care a bit about it, but not as much as I care about the size difference. Feel free to skip the time performance impact for now. Thanks, -Stolee