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List:       git
Subject:    Re: hosting git on a nfs
From:       "Kyle Moffett" <kyle () moffetthome ! net>
Date:       2008-11-14 14:31:09
Message-ID: f73f7ab80811140631h44f0c712h5656cd6664d91380 () mail ! gmail ! com
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On Thu, Nov 13, 2008 at 8:15 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>  - It would be really cool to find some way to automatically notice when
>   the tree is hot-cached and we might as well just be linear. I don't
>   know exactly what it might be, but one of the nice things is that the
>   preloading is _entirely_ optimistic, and we could just stop it in the
>   middle if we notice that there's no upside.

Perhaps, rather... notice when the tree is *cold*-cached.  At that
point you're already in a pseudo-slowpath and starting several threads
won't be noticeable at all compared to the time savings.  You could
probably very easily do that by keeping track of the time as you start
with the normal single-threaded scan of directory entries.  If the
entries are all equally slow/fast, there most likely won't be any
benefit at all to spawning extra threads.  You might use some cutoff
on number of entries to test before you assume everything is hot and
stop worrying about the time.  If there's a lot of variability in the
first few thousand then it means some caches are cold and spawning
extra threads will probably help.

Cheers,
Kyle Moffett
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