From: Karthik Nayak Date: Tue, 06 Oct 2026 09:36:33 GMT Subject: Re: [PATCH v2] packed-refs: use `fwrite()` when passing refs verbatim Message-ID: In-Reply-To: <87zewsf13b.fsf@dev.null.iotcl.com.invalid> Toon Claes writes: > Karthik Nayak writes: > >> The `write_with_updates()` function uses a `struct ref_iterator` to >> iterate over all refs to write to the temporary packed-refs file. It >> receives the iterator from `packed_ref_iterator_begin()` which takes a >> snapshot of the 'packed-refs' file. >> >> While writing to the new packed-refs file, writes are routed via >> `write_packed_entry()` which uses `fprintf()`. Even for references which >> haven't changed, we use the same mechanism. Instead, let's track the >> position of unchanged references in the snapshot iterator and directly >> use `fwrite()`. >> >> With this, any sanitation which was happening as a side of reformatting > > s/side/side effect/ ? > That's probably better. >> is now lost. But that was never the job of this section of the code, >> since the main intention is to simply rewrite the remaining refs post >> deletion of the selective few. > > Agreed. > >> >> This removes the unnecessary formatting operation involved. We can see a >> consistent ~20% performance improvement when deleting from packed >> references. >> >> Benchmark 1: update-ref: delete ref (refcount = 100000, revision = master) >> Time (mean ± σ): 28.7 ms ± 1.7 ms [User: 22.5 ms, System: 5.9 ms] >> Range (min … max): 26.7 ms … 33.3 ms 46 runs >> >> Benchmark 2: update-ref: delete ref (refcount = 100000, revision = b4/kn-speedup-packed-refs) >> Time (mean ± σ): 23.8 ms ± 1.2 ms [User: 17.5 ms, System: 6.0 ms] >> Range (min … max): 22.1 ms … 27.7 ms 56 runs >> >> Summary >> update-ref: delete ref (refcount = 100000, revision = b4/kn-speedup-packed-refs) ran >> 1.21 ± 0.09 times faster than update-ref: delete ref (refformat = files, refcount = 100000, revision = master) >> >> Signed-off-by: Karthik Nayak >> --- >> Changes in v2: >> - Instead of using the existing function, introduce a new >> `write_packed_entry_raw()`. >> - Modify the commit to also note that we lose sanitization. > > s/commit/commit message/ > This doesn't go into the commit itself, so I'll leave it as is. >> - Link to v1: https://patch.msgid.link/20260930-kn-speedup-packed-refs-v1-1-111cd03d9b0e@gmail.com > > Okay, I'm okay with this version. > > -- > Laters, > Toon Thanks for the review.