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From: Chris Torek <>
To: Junio C Hamano <>
Cc: Neeraj Singh <>,
	Jeff Hostetler <>,
	Git List <>,
	"Neeraj K. Singh" <>
Subject: Re: [PATCH] read-cache: make the index write buffer size 128K
Date: Wed, 24 Feb 2021 22:58:36 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <xmqqmtvswvp7.fsf@gitster.g>

> Neeraj Singh <> writes:
> > I collected data from an experiment with different buffer sizes on Windows on my
> > 3.6Ghz Xeon W-2133 machine:
> >
> >
> > The timing is pretty much in the noise after we pass 32K.  So I think
> > 8K is too small, but
> > given the flatness of the curve we can feel good about any value above
> > 32K from a performance
> > perspective.  I still think 128K is a decent number that won't likely
> > need to be changed for
> > some time.

Linux/BSD/etc `stat` system calls report st_blksize values to tell
user code the optimal size for read and write calls.  Does Windows
have one?  (It's not POSIX but is XSI.)

(How *well* the OS reports `st_blksize` is another question
entirely, but at least if the report says, say, 128k, and that's
wrong, that's no longer Git's fault. :-) )

On Wed, Feb 24, 2021 at 10:46 PM Junio C Hamano <> wrote:
> Thanks for a supporting graph.
> I can very well imagine that it would have been tempting to instead
> say "after we pass 128k" while explaining exactly the same graph,
> and doing so would have given a more coherent argument to support
> the choice of 128k the patch made.  You knew that a "then perhaps we
> can reclaim 96k by sizing the buffer down a bit?" would become a
> reasonable response, but you still chose to be honest, which I kinda
> like ;-)

128K is correct for ZFS; 64K is typically correct for UFS2; 8K is
the old UFS1 size.  Anything under that has been too small for
a long time. :-)


  reply	other threads:[~2021-02-25  7:00 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-18  2:48 [PATCH] read-cache: make the index write buffer size 128K Neeraj K. Singh via GitGitGadget
2021-02-19 19:12 ` Jeff Hostetler
2021-02-20  3:28   ` Junio C Hamano
2021-02-20  7:56     ` Neeraj Singh
2021-02-21 12:51       ` Junio C Hamano
2021-02-24 20:56         ` Neeraj Singh
2021-02-25  5:41           ` Junio C Hamano
2021-02-25  6:58             ` Chris Torek [this message]
2021-02-25  7:16               ` Junio C Hamano
2021-02-25  7:36                 ` Neeraj Singh
2021-02-25  7:57                   ` Chris Torek

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