Re: [PATCH] fs/proc: Move kfree outside pde_unload_lock

[Nathan Zimmer]

On 08/24/2012 09:58 AM, Eric Dumazet wrote:
> Le vendredi 24 aoÃt 2012 Ã 09:48 -0500, Nathan Zimmer a Ãcrit :
> > On Wed, Aug 22, 2012 at 11:42:58PM +0200, Eric Dumazet wrote:
> > > On Wed, 2012-08-22 at 20:28 +0200, Eric Dumazet wrote:
> > >
> > > > Thats interesting, but if you really want this to fly, one RCU
> > > > conversion would be much better ;)
> > > >
> > > > pde_users would be an atomic_t and you would avoid the spinlock
> > > > contention.
> > > Here is what I had in mind, I would be interested to know how it helps a 512 core machine ;)
> > Here are the results and they look great.
> >
> > cpuinfo	baseline	moved kfree	Rcu
> > tasks	read-sec	read-sec	read-sec
> > 1	0.0141		0.0141		0.0141
> > 2	0.0140		0.0140		0.0142
> > 4	0.0140		0.0141		0.0141
> > 8	0.0145		0.0145		0.0140
> > 16	0.0553		0.0548		0.0168
> > 32	0.1688		0.1622		0.0549
> > 64	0.5017		0.3856		0.1690
> > 128	1.7005		0.9710		0.5038
> > 256	5.2513		2.6519		2.0804
> > 512	8.0529		6.2976		3.0162
> Indeed...
>
> Could you explicit the test you are actually doing ?
>
> Thanks


It is a dead simple test.
The test starts by forking off X number of tasks
assigning each their own cpu.
Each task then allocs a bit of memory.
All tasks wait on a memory cell for the go order.
We measure the read time starting here.
Once the go order is given they all read a chunk of the selected proc file.
I was using /proc/cpuinfo to test.
Once everyone has finished we take the end read time.




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