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SubjectRe: A Plumber’s Wish List for Linux
On Fri, Oct 14, 2011 at 8:38 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
>
> Well, wouldn't it be better to pull that complexity to userspace?
> After all, moving tasks from a cgroup to another is not a performance
> critical operation so that probably doesn't need to be all handled by
> the kernel.

I'd always assumed that too, but apparently on very many (possibly the
majority of?) Linux systems, it actually is performance-critical.

Specifically, Android bounces tasks in and out of a "foreground
low-latency" cpu cgroup at a fairly high rate, and has found the
performance hit from the locking to be a problem on multi-core phones.
Hence Colin Cross' patches for avoid calls to synchronize_rcu() in the
attach path.

Paul


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