On Wed, 7 Jan 2009, Chris Mason wrote:
>
> So far I haven't found any btrfs benchmarks where this is slower than
> mutexes without any spinning. But, it isn't quite as fast as the btrfs
> spin.
Quite frankly, from our history with ext3 and other filesystems, using a
mutex in the filesystem is generally the wrong thing to do anyway.
Are you sure you can't just use a spinlock, and just release it over IO?
The "have to do IO or extend the btree" case is usually pretty damn clear.
Because it really sounds like you're lock-limited, and you should just try
to clean it up. A pure "just spinlock" in the hotpath is always going to
be better.
Linus
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