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List:       fuse-devel
Subject:    Re: [fuse-devel] stat performance on multicore systems: measurements
From:       Anand Avati <anand.avati () gmail ! com>
Date:       2012-08-03 21:38:18
Message-ID: CAFboF2wu27+cb9_CMj6CUEp+rjcXWdZ8H1fX2znbDz9SmhTdvA () mail ! gmail ! com
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On Fri, Aug 3, 2012 at 11:19 AM, Stefan Westerfeld <stefan@space.twc.de>wrote:

>    Hi!
>
> On Wed, Aug 01, 2012 at 09:19:29PM +0200, Miklos Szeredi wrote:
> > On Wed, Aug 1, 2012 at 6:41 PM, Stefan Westerfeld <stefan@space.twc.de>
> wrote:
> > > Your patch doesn't compile here:
> > >
> > > Linux ubuntu 3.2.21 #2 SMP Fri Jul 27 12:56:14 CEST 2012 x86_64 x86_64
> x86_64 GNU/Linux
> > >
> > > root@ubuntu:/usr/src/linux-source-3.2.0/linux-source-3.2.0# LANG=C
> make
> > > [...]
> > >   CC [M]  fs/fuse/dev.o
> > > fs/fuse/dev.c: In function 'queue_request':
> > > fs/fuse/dev.c:271:3: error: too many arguments to function
> '__wake_up_locked'
> > > include/linux/wait.h:160:6: note: declared here
> > >
> >
> > Please remove the last argument of __wake_up_locked() and try that.
>
> Well, it compiles, but I still don't see any performance improvement with
> the
> patch applied.



I think we really need multiple request queues (as many number of CPUs)
which are processed by multiple user-space fuse threads which bind
themselves to one CPU each and syscalls add their request to the queue
belonging to the CPU they are happening in -- all of this working without
any cross-cpu shared data. We could optionally have some starvation
avoidance by making another CPU's fuse thread pick this CPU's requests if
it is too idle and this CPU has too many requests, but it need not be an
initial feature. If all this really improves performance to the same extent
(and hence corroborates the theory), the extra complexity would be well
worth it.

Thanks,
Avati
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