Re: [patch 00/10] [RFC] SLUB patches for more functionality, performance and maintenance

[Martin Bligh <mbligh@mbligh.org>]

Christoph Lameter wrote:
> On Mon, 9 Jul 2007, Martin Bligh wrote:
> 
>> Those numbers came from Mathieu Desnoyers (LTTng) if you
>> want more details.
> 
> Okay the source for these numbers is in his paper for the OLS 2006: Volume 
> 1 page 208-209? I do not see the exact number that you referred to there.

Nope, he was a direct co-author on the paper, was
working here, and measured it.

> He seems to be comparing spinlock acquire / release vs. cmpxchg. So I 
> guess you got your material from somewhere else?
> 
> Also the cmpxchg used there is the lockless variant. cmpxchg 29 cycles w/o 
> lock prefix and 112 with lock prefix.
> 
> I see you reference another paper by Desnoyers: 
> http://tree.celinuxforum.org/CelfPubWiki/ELC2006Presentations?action=AttachFile&do=get&target=celf2006-desnoyers.pdf
> 
> I do not see anything relevant there. Where did those numbers come from?
> 
> The lockless cmpxchg is certainly an interesting idea. Certain for some 
> platforms I could disable preempt and then do a lockless cmpxchg.

Matheiu, can you give some more details? Obviously the exact numbers
will vary by archicture, machine size, etc, but it's a good point
for discussion.

M.