Re: Performance versus FreeBSD 7.0

[Cyrus Massoumi <cyrusm@gmx.net>]

Nick Piggin wrote:
> 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@gmail.com>
>>> 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.

Thanks for pointing this out Nick.