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Re: [PATCH v2] read_index_from(): Skip verification of the cache entry order to speed index loading

From
AVAlex Vandiver <alexmv@dropbox.com>
Date
Oct 31, 2017, 00:33 UTC
Message-ID
<alpine.DEB.2.10.1710301727160.10801@alexmv-linux>
In-Reply-To
<20171030180334.ddursnmj5wqgimqu@sigill.intra.peff.net>
On Mon, 30 Oct 2017, Jeff King wrote:
Show 6 quoted lines
> On Mon, Oct 30, 2017 at 08:48:48AM -0400, Ben Peart wrote:
> 
> > Any updates or thoughts on this one?  While the patch has become quite
> > trivial, it does results in a savings of 5%-15% in index load time.
> 
> I like the general direction of avoiding the check during each read.
Same -- the savings here are well worth it, IMHO.
Show 9 quoted lines
> > I thought the compromise of having this test only run when DEBUG is defined
> > should limit it to developer builds (hopefully everyone developing on git is
> > running DEBUG builds :)).  Since the test is trying to detect buggy code
> > when writing the index, I thought that was the right time to test/catch any
> > issues.
> 
> I certainly don't build with DEBUG. It traditionally hasn't done
> anything useful. But I'm also not convinced that this is a likely way to
> find bugs in the first place, so I'm OK missing out on it.

I also don't compile with DEBUG -- there's no documentation that mentions it, and I don't think I'd considered going poking for what was `#ifdef`d. I think it'd be reasonable to provide some configure-time setting that adds `CFLAGS="-ggdb3 -O0 -DDEBUG"` or similar, but that seems possibly moot for this particular change (see below).

> But what we probably _do_ need is to make sure that "git fsck" would
> detect such an out-of-order index. So that developers and users alike
> can diagnose suspected problems.
Agree -- that seems like a better home for this logic.
> > I am working on other, more substantial savings for index load times
> > (stay tuned) but this seemed like a small simple way to help speed
> > things up.
I'm interested to hear more about what direction you're looking in here.
 - Alex
Previous: Jeff KingNext: Ben Peart
Message 13 of 18 in “read_index_from(): Skip verification of the cache entry order to speed index loading”
  1. read_index_from(): Skip verification of the cache entry order to speed index loadingBen Peart, Oct 18, 2017
  2. Junio C HamanoOct 19, 2017
  3. Ben PeartOct 19, 2017
  4. Jeff KingOct 19, 2017
  5. Junio C HamanoOct 20, 2017
  6. Stefan BellerOct 19, 2017
  7. Johannes SchindelinOct 20, 2017
  8. Stefan BellerOct 20, 2017
  9. Junio C HamanoOct 21, 2017
  10. read_index_from(): Skip verification of the cache entry order to speed index loadingBen Peart, Oct 24, 2017
  11. Ben PeartOct 30, 2017
  12. Jeff KingOct 30, 2017
  13. Alex VandiverOct 31, 2017
  14. Ben PeartOct 31, 2017
  15. Jeff KingOct 31, 2017
  16. Junio C HamanoNov 1, 2017
  17. Junio C HamanoOct 31, 2017
  18. Ben PeartOct 31, 2017

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