From: Patrick Steinhardt <ps@pks.im>
To: git@vger.kernel.org, Han-Wen Nienhuys <hanwenn@gmail.com>,
Karthik Nayak <karthik.188@gmail.com>
Subject: Re: [PATCH v2 10/10] reftable/block: avoid copying block iterators on seek
Date: Tue, 9 Apr 2024 05:18:45 +0200 [thread overview]
Message-ID: <ZhSzla7GwfdokQbG@tanuki> (raw)
In-Reply-To: <vab3mzg3meohikmfl5v57uxj6w7w2odrx7cvhmoto7am2bl2yt@6l4salel4ko5>
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On Mon, Apr 08, 2024 at 08:29:14PM -0500, Justin Tobler wrote:
> On 24/04/08 02:17PM, Patrick Steinhardt wrote:
> > When seeking a reftable record in a block we need to position the
> > iterator _before_ the sought-after record so that the next call to
> > `block_iter_next()` would yield that record. To achieve this, the loop
> > that performs the linear needs to restore the previous position once it
>
> Did we mean to say "linear seek" here? Otherwise this looks good to me.
>
> -Justin
Oh, yes, of course. Thanks for reading this carefully!
Patrick
> > has found the record.
> >
> > This is done by advancing two `block_iter`s: one to check whether the
> > next record is our sought-after record, and one that we update after
> > every iteration. This of course involves quite a lot of copying and also
> > leads to needless memory allocations.
> >
> > Refactor the code to get rid of the `next` iterator and the copying this
> > involves. Instead, we can restore the previous offset such that the call
> > to `next` will return the correct record.
> >
> > Next to being simpler conceptually this also leads to a nice speedup.
> > The following benchmark parser 10k refs out of 100k existing refs via
> > `git-rev-list --no-walk`:
> >
> > Benchmark 1: rev-list: print many refs (HEAD~)
> > Time (mean ± σ): 170.2 ms ± 1.7 ms [User: 86.1 ms, System: 83.6 ms]
> > Range (min … max): 166.4 ms … 180.3 ms 500 runs
> >
> > Benchmark 2: rev-list: print many refs (HEAD~)
> > Time (mean ± σ): 161.6 ms ± 1.6 ms [User: 78.1 ms, System: 83.0 ms]
> > Range (min … max): 158.4 ms … 172.3 ms 500 runs
> >
> > Summary
> > rev-list: print many refs (HEAD) ran
> > 1.05 ± 0.01 times faster than rev-list: print many refs (HEAD~)
> >
> > Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ...
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next prev parent reply other threads:[~2024-04-09 3:19 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-27 6:36 [PATCH 0/9] reftable: optimize table and block iterators Patrick Steinhardt
2024-03-27 6:36 ` [PATCH 1/9] reftable/block: rename `block_reader_start()` Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 2/9] reftable/block: merge `block_iter_seek()` and `block_reader_seek()` Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 3/9] reftable/block: better grouping of functions Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 4/9] reftable/block: introduce `block_reader_release()` Patrick Steinhardt
2024-04-03 13:16 ` Karthik Nayak
2024-04-08 12:10 ` Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 5/9] reftable/block: move ownership of block reader into `struct table_iter` Patrick Steinhardt
2024-04-03 4:52 ` Justin Tobler
2024-04-03 13:10 ` Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 6/9] reftable/reader: iterate to next block in place Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 7/9] reftable/block: reuse uncompressed blocks Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 8/9] reftable/block: open-code call to `uncompress2()` Patrick Steinhardt
2024-03-27 6:37 ` [PATCH 9/9] reftable/block: reuse `zstream` state on inflation Patrick Steinhardt
2024-04-03 13:33 ` [PATCH 0/9] reftable: optimize table and block iterators Karthik Nayak
2024-04-08 12:16 ` [PATCH v2 00/10] " Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 01/10] reftable/block: rename `block_reader_start()` Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 02/10] reftable/block: merge `block_iter_seek()` and `block_reader_seek()` Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 03/10] reftable/block: better grouping of functions Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 04/10] reftable/block: introduce `block_reader_release()` Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 05/10] reftable/block: move ownership of block reader into `struct table_iter` Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 06/10] reftable/reader: iterate to next block in place Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 07/10] reftable/block: reuse uncompressed blocks Patrick Steinhardt
2024-04-08 12:16 ` [PATCH v2 08/10] reftable/block: open-code call to `uncompress2()` Patrick Steinhardt
2024-04-08 12:17 ` [PATCH v2 09/10] reftable/block: reuse `zstream` state on inflation Patrick Steinhardt
2024-04-10 10:15 ` Karthik Nayak
2024-04-08 12:17 ` [PATCH v2 10/10] reftable/block: avoid copying block iterators on seek Patrick Steinhardt
2024-04-09 1:29 ` Justin Tobler
2024-04-09 3:18 ` Patrick Steinhardt [this message]
2024-04-09 1:32 ` [PATCH v2 00/10] reftable: optimize table and block iterators Justin Tobler
2024-04-10 11:35 ` Karthik Nayak
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