Re: [PATCH 1/3] sysfs directory scaling: rbtree for dirent namelookups
From: Greg KH
Date: Tue Nov 03 2009 - 11:10:39 EST
On Tue, Nov 03, 2009 at 07:14:33AM +0100, Eric Dumazet wrote:
> Greg KH a ?crit :
> > On Sun, Nov 01, 2009 at 11:31:30AM -0500, Benjamin LaHaise wrote:
> >> Use an rbtree in sysfs_dirent to speed up file lookup times
> >> Systems with large numbers (tens of thousands and more) of network
> >> interfaces stress the sysfs code in ways that make the linear search for
> >> a name match take far too long. Avoid this by using an rbtree.
> > What kind of speedups are you seeing here? And do these changes cause a
> > memory increase due to the structure changes which outweigh the
> > speedups?
> > What kind of test are you doing to reproduce this?
> Its curious because in my tests the biggest problems come from
> kernel/sysctl.c (__register_sysctl_paths) consuming 80% of cpu
> in following attempt to create 20.000 devices
> (disable hotplug before trying this, and ipv6 too !)
> modprobe dummy numdummies=20000
> I believe we should address __register_sysctl_paths() scalability
> problems too.
But registering 20000 devices is a far different problem from using
those 20000 devices :)
I think the "use the device" path should be the one we care the most
about fixing up, as that is much more common than the register path for
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