linux-kernel - RE: [PATCH 1/3] slub: set a criteria for slub node partial adding

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Date:	Wed, 14 Dec 2011 14:56:52 +0800
From:	"Alex,Shi" <alex.shi@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	"penberg@...nel.org" <penberg@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: RE: [PATCH 1/3] slub: set a criteria for slub node partial adding


> > Thanks for the data. Real netperf is hard to give enough press on SLUB.
> > but as I mentioned before, I also didn't find real performance change on
> > my loopback netperf testing. 
> > 
> > I retested hackbench again. about 1% performance increase still exists
> > on my 2 sockets SNB/WSM and 4 sockets NHM.  and no performance drop for
> > other machines. 
> > 
> > Christoph, what's comments you like to offer for the results or for this
> > code change? 
> 
> I believe far more aggressive mechanism is needed to help these
> workloads.
> 
> Please note that the COLD/HOT page concept is not very well used in
> kernel, because its not really obvious that some decisions are always
> good (or maybe this is not well known)

Hope Christoph know everything of SLUB. :) 
> 
> We should try to batch things a bit, instead of doing a very small unit
> of work in slow path.
> 
> We now have a very fast fastpath, but inefficient slow path.
> 
> SLAB has a litle cache per cpu, we could add one to SLUB for freed
> objects, not belonging to current slab. This could avoid all these
> activate/deactivate overhead.

Maybe worth to try or maybe Christoph had studied this? 


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