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[104.178.186.189]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a806c2aeb0sm77016585a.44.2024.08.29.12.01.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2024 12:01:37 -0700 (PDT) Date: Thu, 29 Aug 2024 15:01:36 -0400 From: Taylor Blau To: Jeff King Cc: git@vger.kernel.org, Junio C Hamano Subject: Re: [PATCH 5/8] pack-bitmap-write.c: select pseudo-merges even for small bitmaps Message-ID: References: <0fea7803d86ca17451af408e1bf93c32690edc44.1723743050.git.me@ttaylorr.com> <20240817103401.GB551779@coredump.intra.peff.net> Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240817103401.GB551779@coredump.intra.peff.net> On Sat, Aug 17, 2024 at 06:34:01AM -0400, Jeff King wrote: > On Thu, Aug 15, 2024 at 01:31:12PM -0400, Taylor Blau wrote: > > > Ordinarily, the pack-bitmap machinery will select some subset of > > reachable commits to receive bitmaps. But when there are fewer than 100 > > commits indexed in the first place, they will all receive bitmaps as a > > special case. > > > > When this happens, pseudo-merges are not generated, making it impossible > > to test pseudo-merge corner cases with fewer than 100 commits. > > > > Select pseudo-merges even for bitmaps with fewer than 100 commits to > > make such testing easier. In practice, this should not make a difference > > to non-testing bitmaps, as they are unlikely to be used when a > > repository has so few commits to begin with. > > I think you could argue that if there are fewer than 100 commits in the > history that pseudo-merge bitmaps are overkill, so it does not matter > much either way. But I think being consistent with our behavior (i.e., > generating them if asked) is important for testing and debugging. Oh, I think that argument is very fair and makes a lot of sense. The point of this patch wasn't that having pseudo-merge bitmaps for repositories that small (and which already have complete bitmap coverage!) is helpful for performance. Rather, it was to make it easier to test the pseudo-merge code path in small repositories without having to waste CPU cycles to generate 98 extra commits when 2 would do, etc. Thanks, Taylor