Re: [GIT PULL] adaptive spinning mutexes

[Bill Davidsen]

Chris Mason wrote:
> On Thu, 2009-01-15 at 10:16 -0800, Linus Torvalds wrote:
> > On Thu, 15 Jan 2009, Ingo Molnar wrote:
> > > btw., i think spin-mutexes have a design advantage here: in a lot of code 
> > > areas it's quite difficult to use spinlocks - cannot allocate memory, 
> > > cannot call any code that can sporadically block (but does not _normally_ 
> > > block), etc.
> > >
> > > With mutexes those atomicity constraints go away - and the performance 
> > > profile should now be quite close to that of spinlocks as well.
> > Umm. Except if you wrote the code nicely and used spinlocks, you wouldn't 
> > hold the lock over all those unnecessary and complex operations.
>
> While this is true, there are examples of places we should expect
> speedups for this today.
>
> Concurrent file creation/deletion in a single dir will often find things
> hot in cache and not have to block anywhere (mail spools).
And although not as common, NNTP servers using file per article storage.

> Concurrent O_DIRECT aio writes to the same file, where i_mutex is
> dropped early on.
>
> pipes should see a huge improvement.
I'd like to see that. Didn't realize how slow pipes really are.

> I'll kick off some runs of my three benchmarks on ext3 for comparison.
> If there are things less synthetic people would like to see, please let
> me know.
>
> -chris
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


--
Bill Davidsen <davidsen@xxxxxxx>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/