Re: [PATCH 0/7] reftable: memory optimizations for reflog iteration

[Patrick Steinhardt <ps@pks.im>]

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On Mon, Mar 11, 2024 at 12:41:19PM -0700, Josh Steadmon wrote:
> On 2024.03.05 13:10, Patrick Steinhardt wrote:
> > Hi,
> > 
> > this patch series does the same as all the preceding patch series that
> > optimized how the reftable library iterates through refs, but for
> > reflogs instead.
> > 
> > The goal of this patch series is to arrive at a constant number of
> > allocations when iterating refs. This is achieved in mostly the same way
> > we did it for ref iteration, namely by reusing already-allocated memory.
> > Overall, this brings us down from 8 allocations per reflog record to
> > essentially 0 allocations per reflog. Iterating through 1 million
> > reflogs with `git reflog list` thus goes down from 8.068m allocations to
> > only around 68.5k.
> > 
> > This series is built on top of "master" at b387623c12 (The third batch,
> > 2024-03-01) with Junio's "ps/reftable-iteration-perf-part2" at
> > 43f70eaea0 (refs/reftable: precompute prefix length, 2024-03-04) merged
> > into it.
> > 
> > Patrick
> > 
> > Patrick Steinhardt (7):
> >   refs/reftable: reload correct stack when creating reflog iter
> >   reftable/record: convert old and new object IDs to arrays
> >   reftable/record: avoid copying author info
> >   reftable/record: reuse refnames when decoding log records
> >   reftable/record: reuse message when decoding log records
> >   reftable/record: use scratch buffer when decoding records
> >   refs/reftable: track last log record name via strbuf
> > 
> >  refs/reftable-backend.c    |  52 +++++----------
> >  reftable/block.c           |   4 +-
> >  reftable/block.h           |   2 +
> >  reftable/merged_test.c     |  11 ++--
> >  reftable/readwrite_test.c  |  62 +++++++-----------
> >  reftable/record.c          | 129 ++++++++++++++-----------------------
> >  reftable/record.h          |   5 +-
> >  reftable/record_test.c     |  68 ++++++++++---------
> >  reftable/reftable-record.h |   6 +-
> >  reftable/stack_test.c      |  26 ++++----
> >  10 files changed, 154 insertions(+), 211 deletions(-)
> > 
> > -- 
> > 2.44.0
> > 
> 
> This series looks good to me (with one request that we add a test for
> patch #1 if possible).
> 
> Reviewed-by: Josh Steadmon <steadmon@google.com>

Thanks for your review!

Patrick

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