Re: [PATCH 1/3] slub: set a criteria for slub node partial adding

["Alex,Shi" <alex.shi@intel.com>]

On Fri, 2011-12-02 at 19:36 +0800, Eric Dumazet wrote:
> Le vendredi 02 dA(C)cembre 2011 A  16:23 +0800, Alex Shi a A(C)crit :
> > From: Alex Shi <alexs@intel.com>
> > 
> > Times performance regression were due to slub add to node partial head
> > or tail. That inspired me to do tunning on the node partial adding, to
> > set a criteria for head or tail position selection when do partial
> > adding.
> > My experiment show, when used objects is less than 1/4 total objects
> > of slub performance will get about 1.5% improvement on netperf loopback
> > testing with 2048 clients, wherever on our 4 or 2 sockets platforms,
> > includes sandbridge or core2.
> > 
> > Signed-off-by: Alex Shi <alex.shi@intel.com>
> > ---
> >  mm/slub.c |   18 ++++++++----------
> >  1 files changed, 8 insertions(+), 10 deletions(-)
> > 
> 
> netperf (loopback or ethernet) is a known stress test for slub, and your
> patch removes code that might hurt netperf, but benefit real workload.
> 
> Have you tried instead this far less intrusive solution ?
> 
> if (tail == DEACTIVATE_TO_TAIL ||
>     page->inuse > page->objects / 4)
>          list_add_tail(&page->lru, &n->partial);
> else
>          list_add(&page->lru, &n->partial);

For loopback netperf, it has no clear performance change on all
platforms. 
For hackbench testing, it has a bit worse on 2P NHM 0.5~1%, but it is
helpful to increase about 2% on 4P(8cores * 2SMT) NHM machine. 

I was thought no much cache effect on hot or cold after per cpu partial
adding. but seems for hackbench, node partial still has much effect. 


> 
> 
> 


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