From: Jeff King <peff@peff.net>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 1/2] compat: move unaligned helpers to bswap.h
Date: Thu, 23 Jan 2014 14:44:01 -0500 [thread overview]
Message-ID: <20140123194401.GA31412@sigill.intra.peff.net> (raw)
In-Reply-To: <20140123194118.GT18964@google.com>
On Thu, Jan 23, 2014 at 11:41:18AM -0800, Jonathan Nieder wrote:
> Jeff King wrote:
>
> > Commit d60c49c (read-cache.c: allow unaligned mapping of the
> > index file, 2012-04-03) introduced helpers to access
> > unaligned data. Let's factor them out to make them more
> > widely available.
> >
> > While we're at it, we'll give the helpers more readable
> > names, add a helper for the "ntohll" form, and add the
> > appropriate Makefile knob.
>
> Weird. Why wasn't git broken on the relevant platforms before (given
> that no one has been setting NEEDS_ALIGNED_ACCESS for them)?
Because most of our data structures support aligned access. Thomas
mentioned this as a potential issue earlier, and I said in a re-roll
cover letter:
I did not include the NEEDS_ALIGNED_ACCESS patch. I note that we do
not even have a Makefile knob for this, and the code in read-cache.c
has probably never actually been used. Are there real systems that
have a problem? The read-cache code was in support of the index v4
experiment, which did away with the 8-byte padding. So it could be
that we simply don't see it, because everything is currently aligned.
I think it was a bug waiting to surface if index v4 ever got wide use.
-Peff
next prev parent reply other threads:[~2014-01-23 19:44 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-21 13:56 [PATCH v4 0/22] pack bitmaps Jeff King
2013-12-21 13:59 ` [PATCH v4 01/23] sha1write: make buffer const-correct Jeff King
2013-12-22 9:06 ` Christian Couder
2013-12-21 13:59 ` [PATCH v4 02/23] revindex: Export new APIs Jeff King
2013-12-21 13:59 ` [PATCH v4 03/23] pack-objects: Refactor the packing list Jeff King
2013-12-21 13:59 ` [PATCH v4 04/23] pack-objects: factor out name_hash Jeff King
2013-12-21 13:59 ` [PATCH v4 05/23] revision: allow setting custom limiter function Jeff King
2013-12-21 13:59 ` [PATCH v4 06/23] sha1_file: export `git_open_noatime` Jeff King
2013-12-21 13:59 ` [PATCH v4 07/23] compat: add endianness helpers Jeff King
2013-12-21 13:59 ` [PATCH v4 08/23] ewah: compressed bitmap implementation Jeff King
2014-01-23 2:05 ` Jonathan Nieder
2014-01-23 18:33 ` Jeff King
2014-01-23 18:35 ` [PATCH 1/2] compat: move unaligned helpers to bswap.h Jeff King
2014-01-23 19:41 ` Jonathan Nieder
2014-01-23 19:44 ` Jeff King [this message]
2014-01-23 19:56 ` Jonathan Nieder
2014-01-23 20:04 ` Jeff King
2014-01-23 20:08 ` Jonathan Nieder
2014-01-23 20:09 ` Jeff King
2014-01-23 18:35 ` [PATCH 2/2] ewah: support platforms that require aligned reads Jeff King
2014-01-23 19:52 ` [PATCH v4 08/23] ewah: compressed bitmap implementation Jonathan Nieder
2014-01-23 20:03 ` Jeff King
2014-01-23 20:12 ` Jonathan Nieder
2014-01-23 20:13 ` Jeff King
2014-01-23 20:23 ` Jonathan Nieder
2014-01-23 20:29 ` Jeff King
2014-01-23 20:38 ` Jeff King
2014-01-23 20:14 ` Shawn Pearce
2014-01-23 20:26 ` Jeff King
2014-01-23 21:53 ` brian m. carlson
2014-01-23 22:07 ` Jeff King
2014-01-23 22:17 ` Jonathan Nieder
2014-01-23 22:26 ` Jeff King
2014-01-23 22:33 ` Jonathan Nieder
2014-01-23 20:18 ` Jonathan Nieder
2014-01-23 21:20 ` [PATCH v2 0/3] unaligned reads from .bitmap files Jeff King
2014-01-23 21:23 ` [PATCH 1/3] block-sha1: factor out get_be and put_be wrappers Jeff King
2014-01-23 23:19 ` Jonathan Nieder
2014-01-23 21:26 ` [PATCH 2/3] read-cache: use get_be32 instead of hand-rolled ntoh_l Jeff King
2014-01-23 23:34 ` Jonathan Nieder
2014-01-24 2:22 ` Jeff King
2014-01-23 21:27 ` [PATCH 3/3] ewah: support platforms that require aligned reads Jeff King
2014-01-23 23:44 ` Jonathan Nieder
2014-01-23 23:49 ` Vicent Martí
2014-01-24 0:15 ` Jonathan Nieder
2014-01-23 23:17 ` [PATCH v2 0/3] unaligned reads from .bitmap files Jonathan Nieder
2013-12-21 13:59 ` [PATCH v4 09/23] documentation: add documentation for the bitmap format Jeff King
2013-12-21 14:00 ` [PATCH v4 10/23] pack-bitmap: add support for bitmap indexes Jeff King
2013-12-21 14:00 ` [PATCH v4 11/23] pack-objects: split add_object_entry Jeff King
2013-12-21 14:00 ` [PATCH v4 12/23] pack-objects: use bitmaps when packing objects Jeff King
2013-12-21 14:00 ` [PATCH v4 13/23] rev-list: add bitmap mode to speed up object lists Jeff King
2013-12-21 14:00 ` [PATCH v4 14/23] pack-objects: implement bitmap writing Jeff King
2013-12-21 14:00 ` [PATCH v4 15/23] repack: stop using magic number for ARRAY_SIZE(exts) Jeff King
2013-12-21 14:00 ` [PATCH v4 16/23] repack: turn exts array into array-of-struct Jeff King
2013-12-21 14:00 ` [PATCH v4 17/23] repack: handle optional files created by pack-objects Jeff King
2013-12-21 14:00 ` [PATCH v4 18/23] repack: consider bitmaps when performing repacks Jeff King
2013-12-21 14:00 ` [PATCH v4 19/23] count-objects: recognize .bitmap in garbage-checking Jeff King
2013-12-21 14:00 ` [PATCH v4 20/23] t: add basic bitmap functionality tests Jeff King
2013-12-21 14:00 ` [PATCH v4 21/23] t/perf: add tests for pack bitmaps Jeff King
2013-12-21 14:00 ` [PATCH v4 22/23] pack-bitmap: implement optional name_hash cache Jeff King
2013-12-21 14:00 ` [PATCH v4 23/23] compat/mingw.h: Fix the MinGW and msvc builds Jeff King
2013-12-25 22:08 ` Erik Faye-Lund
2013-12-28 10:00 ` Jeff King
2013-12-28 10:06 ` Vicent Martí
2013-12-28 15:58 ` Ramsay Jones
2013-12-21 14:03 ` [PATCH v4 0/22] pack bitmaps Jeff King
2013-12-21 14:05 ` Jeff King
2013-12-21 18:34 ` Thomas Rast
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