Bob Friesenhahn <bfrie...@simple.dallas.tx.us> wrote:
> On Tue, 7 Jul 2009, Joerg Schilling wrote:
> >
> > posix_fadvise seems to be _very_ new for Solaris and even though I am
> > frequently reading/writing the POSIX standards mailing list, I was not
> > aware of
> > it.
> >
> > From my tests with star, I cannot see a significant performance increase
> > but it
> > may have a 3% effect........
>
> Based on the prior discussions of using mmap() with ZFS and the way
> ZFS likes to work, my guess is that POSIX_FADV_NOREUSE does nothing at
> all and POSIX_FADV_DONTNEED probably does not work either. These are
> pretty straightforward to implement with UFS since UFS benefits from
> the existing working madvise() functionality.
I did run my tests on UFS...
> ZFS seems to want to cache all read data in the ARC, period.
And this is definitely a conceptional mistake as there are applications like
star that like to benefit from read ahead but that don't like to trash caches.
Jörg
--
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