Re: [patch] mm: vmap area cache

[Nick Piggin <npiggin@suse.de>]

On Mon, Jun 28, 2010 at 09:37:42AM +0100, Steven Whitehouse wrote:
> Hi,
> 
> On Sat, 2010-06-26 at 18:31 +1000, Nick Piggin wrote:
> > On Fri, Jun 25, 2010 at 02:00:17PM +0100, Steven Whitehouse wrote:
> > > Hi,
> > > 
> > > Barry Marson has now tested your patch and it seems to work just fine.
> > > Sorry for the delay,
> > > 
> > > Steve.
> > 
> > Hi Steve,
> > 
> > Thanks for that, do you mean that it has solved thee regression?
> > 
> > Thanks,
> > Nick
> > 
> 
> Yes, thats what I have heard from Barry. He said that it was pretty
> close to the expected performance but did not give any figures. The fact
> that his test actually completes shows that most of the problem has been
> solved,

Thanks, so I think it's good to go.

It is interesting that it is just "close" to expected performance.
The lazy vunmap patch is preventing a global IPI and TLB flush on
all CPUs for every vfree() (amortizing it down to basically nothing
if you are doing just small vmaps).

Unless you are testing on a UP machine, I would have expected
improved performance if you are doing a lot of vmalloc/vfree activity.
It could be that the search is still taking some time, and is
outweighing the gains.

We have a few options for being cleverer, so if you're ever interested
to get more detailed results and find a bit more performance here,
let me know.

And thanks for all the reporting and testing so far.

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