Re: A Plumber’s Wish List for Linux

[Paul Menage]

On Fri, Oct 14, 2011 at 8:38 AM, Frederic Weisbecker <fweisbec@xxxxxxxxx> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/