Re: [Patch 1/3] prefetch the mmap_sem in the fault path

On Thursday 23 February 2006 06:39, Arjan van de Ven wrote:
> On Thu, 2006-02-23 at 07:29 -0500, Jes Sorensen wrote:
> > >>>>> "Arjan" == Arjan van de Ven <[email protected]> writes:
> >
> > Arjan> In a micro-benchmark that stresses the pagefault path, the
> > Arjan> down_read_trylock on the mmap_sem showed up quite high on the
> > Arjan> profile. Turns out this lock is bouncing between cpus quite a
> > Arjan> bit and thus is cache-cold a lot. This patch prefetches the
> > Arjan> lock (for write) as early as possible (and before some other
> > Arjan> somewhat expensive operations). With this patch, the
> > Arjan> down_read_trylock basically fell out of the top of profile.
> >
> > Out of curiousity, how big was the box used for testing? It might be
> > worth investigating if anything can be done to reduce the number of
> > times that lock is taken in the first place.
> >
> > After all, what's a pain on a 4-way tends to be an utter nightmare on
> > a 16-way ;(
>
> most of it was done on a 2 way, but some tests were done on a 4-way.
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Could you share your microbenchmark with us (or point to the source) and we 
can give this a try on larger systems?   

Thanks,
-- 
Ray Bryant
AMD Performance Labs                   Austin, Tx
512-602-0038 (o)                 512-507-7807 (c)

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

---

• References:
  • Re: [Patch 1/3] prefetch the mmap_sem in the fault path
    • From: Jes Sorensen <[email protected]>
  • Re: [Patch 1/3] prefetch the mmap_sem in the fault path
    • From: Arjan van de Ven <[email protected]>

• Prev by Date: [PATCH 12/23] proc: Rewrite the proc dentry flush on exit optimization.
• Next by Date: [PATCH 13/23] proc: Close the race of a process dying durning lookup.
• Previous by thread: Re: [Patch 1/3] prefetch the mmap_sem in the fault path
• Next by thread: Re: [Patch 1/3] prefetch the mmap_sem in the fault path
• Index(es):
  • Date
  • Thread

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]