Re: Performance versus FreeBSD 7.0

[Nick Piggin]

On Tuesday 04 March 2008 06:02, Cyrus Massoumi wrote:
> Nick Piggin wrote:
> > On Saturday 01 March 2008 01:54, Diego Calleja wrote:
> >> El Fri, 29 Feb 2008 08:38:00 -0500, "Stephen Cuppett"
> >> <cuppett@xxxxxxxxx>
> >
> > escribió:
> >>> loads and 1500% at high loads. When compared with the best performing
> >>> Linux kernel (2.6.22 or 2.6.24) performance is 15% better. Results are
> >>
> >> There has been some performance problems with sysbench performance in
> >> linux which made it slower than freebsd, there were some patches to
> >> speed things up, not sure if they have been merged.
> >
> > There definitely were performance problems with threaded malloc/free
> > in the Linux kernel and glibc. Fixes have been merged in both packages,
> > and AFAIK the FreeBSD guys tested with those fixes in place.
> >
> > I think these were never really run into before in part due to MySQL's
> > unscalable heap design makes it not scale well on higher numbers of
> > CPUs anyway, and also made the malloc problems more pronounced (ie.
> > they added a bit to the contention of the single heap lock, which is
> > the big killer here).
>
> IIRC, going to fine-grained file locking gave them a huge boost in this
> particular benchmark (and maybe others).
> As I said on lwn.net Peter Zijlstra posted a patch to break the global
> file list lock about a year ago [1], but I don't think it was ever
> merged. Here [2] are some numbers for the patchset.
>
> [1] http://lkml.org/lkml/2007/1/28/29
> [2] http://lkml.org/lkml/2007/1/28/116

The mysql workload is not constrained by this lock. The important
part (where freebsd saw their gain) is probably fd lookups, which
are lockless in Linux for a long time.

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