Re: [PATCH 1/3] sysfs directory scaling: rbtree for dirent name lookups

From: Eric W. Biederman
Date: Tue Nov 03 2009 - 17:19:03 EST

Benjamin LaHaise <bcrl@xxxxxxxx> writes:

> On Tue, Nov 03, 2009 at 01:32:33PM -0800, Eric W. Biederman wrote:
>> Are your numbers from your application and are they real world?
>> In which case they are interesting, but it would be good if
>> we could also have microbenchmark numbers that just measure
>> the sysfs costs. If nothing else I am seeing a big startup
>> overhead that isn't being subtracted out that makes it hard
>> to see the real costs here.
> They're application based, so there's a bunch of other overhead included
> that won't show up on a microbenchmark. Each interface requires a round
> trip between 2 L2TP daemons, so there are lots of syscalls and other cache
> polluting effects that won't show up on a microbenchmark. One of the L2TP
> daemons is configured not to instantiate any kernel state -- running in
> this mode, it has very little overhead.
> The other thing to note is that the costs posted are how long it takes to
> add an additional 5,000 interfaces in the given range, not the total time
> to add say 35,000 interfaces (I didn't feel like waiting that long).

Ok. That makes a lot more sense. The times you posted ideally would be flat
but they go up from 12s to 60s.

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