From: Jeff King <peff@peff.net>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: Junio C Hamano <gitster@pobox.com>,
Kim Gybels <kgybels@infogroep.be>,
Johannes Schindelin <johannes.schindelin@gmx.de>,
git@vger.kernel.org
Subject: Re: [PATCH 4/6] packed_ref_iterator_begin(): make optimization more general
Date: Wed, 24 Jan 2018 15:32:58 -0500 [thread overview]
Message-ID: <20180124203258.GB7773@sigill.intra.peff.net> (raw)
In-Reply-To: <bf6c0c67430b936738f5e8891b82022d0127acb0.1516791909.git.mhagger@alum.mit.edu>
On Wed, Jan 24, 2018 at 12:14:14PM +0100, Michael Haggerty wrote:
> We can return an empty iterator not only if the `packed-refs` file is
> missing, but also if it is empty or if there are no references whose
> names succeed `prefix`. Optimize away those cases as well by moving
> the call to `find_reference_location()` higher in the function and
> checking whether the determined start position is the same as
> `snapshot->eof`. (This is possible now because the previous commit
> made `find_reference_location()` robust against empty snapshots.)
Makes sense.
> @@ -937,11 +942,6 @@ static struct ref_iterator *packed_ref_iterator_begin(
> iter->snapshot = snapshot;
> acquire_snapshot(snapshot);
>
> - if (prefix && *prefix)
> - start = find_reference_location(snapshot, prefix, 0);
> - else
> - start = snapshot->start;
> -
I did a double-take here that we are now looking at the snapshot without
calling acquire_snapshot(). But that function is just about taking a
refcount on it. The actual acquisition of data happens in
get_snapshot().
-Peff
next prev parent reply other threads:[~2018-01-24 20:33 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-13 16:11 [PATCH] packed_ref_cache: don't use mmap() for small files Kim Gybels
2018-01-13 18:56 ` Johannes Schindelin
2018-01-14 19:14 ` [PATCH v2] " Kim Gybels
2018-01-15 12:17 ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Michael Haggerty
2018-01-15 12:17 ` [PATCH 1/3] SQUASH? Mention that `snapshot::buf` can be NULL for empty files Michael Haggerty
2018-01-15 12:17 ` [PATCH 2/3] create_snapshot(): exit early if the file was empty Michael Haggerty
2018-01-15 12:17 ` [PATCH 3/3] find_reference_location(): don't invoke if `snapshot->buf` is NULL Michael Haggerty
2018-01-17 20:23 ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Johannes Schindelin
2018-01-17 21:52 ` Junio C Hamano
2018-01-15 21:15 ` [PATCH] packed_ref_cache: don't use mmap() for small files Jeff King
2018-01-15 23:37 ` Kim Gybels
2018-01-15 23:52 ` Jeff King
2018-01-16 19:38 ` [PATCH v3] " Kim Gybels
2018-01-17 22:09 ` Jeff King
2018-01-21 4:41 ` Michael Haggerty
2018-01-22 19:31 ` Junio C Hamano
2018-01-24 11:05 ` Michael Haggerty
2018-01-24 11:14 ` [PATCH 0/6] Yet another approach to handling empty snapshots Michael Haggerty
2018-01-24 11:14 ` [PATCH 1/6] struct snapshot: store `start` rather than `header_len` Michael Haggerty
2018-01-24 20:36 ` Jeff King
2018-01-24 11:14 ` [PATCH 2/6] create_snapshot(): use `xmemdupz()` rather than a strbuf Michael Haggerty
2018-01-24 11:14 ` [PATCH 3/6] find_reference_location(): make function safe for empty snapshots Michael Haggerty
2018-01-24 20:27 ` Jeff King
2018-01-24 21:11 ` Junio C Hamano
2018-01-24 21:34 ` Jeff King
2018-01-24 11:14 ` [PATCH 4/6] packed_ref_iterator_begin(): make optimization more general Michael Haggerty
2018-01-24 20:32 ` Jeff King [this message]
2018-01-24 11:14 ` [PATCH 5/6] load_contents(): don't try to mmap an empty file Michael Haggerty
2018-01-24 11:14 ` [PATCH 6/6] packed_ref_cache: don't use mmap() for small files Michael Haggerty
2018-01-24 20:38 ` [PATCH 0/6] Yet another approach to handling empty snapshots Jeff King
2018-01-24 20:54 ` Junio C Hamano
2018-02-15 16:54 ` Johannes Schindelin
2018-01-24 18:05 ` [PATCH v3] packed_ref_cache: don't use mmap() for small files Junio C Hamano
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