[PATCH v2 04/11] memcg: disable softirq in lock_page_cgroup()
kamezawa.hiroyu at jp.fujitsu.com
Sun Oct 17 17:44:37 PDT 2010
On Fri, 15 Oct 2010 14:14:32 -0700
Greg Thelen <gthelen at google.com> wrote:
> If pages are being migrated from a memcg, then updates to that
> memcg's page statistics are protected by grabbing a bit spin lock
> using lock_page_cgroup(). In an upcoming commit memcg dirty page
> accounting will be updating memcg page accounting (specifically:
> num writeback pages) from softirq. Avoid a deadlocking nested
> spin lock attempt by disabling softirq on the local processor
> when grabbing the page_cgroup bit_spin_lock in lock_page_cgroup().
> This avoids the following deadlock:
> CPU 0 CPU 1
> start move
> lock_page_cgroup /* deadlock */
> By disabling softirq in lock_page_cgroup, nested calls are avoided.
> The softirq would be delayed until after inc_file_mapped enables
> softirq when calling unlock_page_cgroup().
> The normal, fast path, of memcg page stat updates typically
> does not need to call lock_page_cgroup(), so this change does
> not affect the performance of the common case page accounting.
> Signed-off-by: Andrea Righi <arighi at develer.com>
> Signed-off-by: Greg Thelen <gthelen at google.com>
I have a patch for this problem.
So, could you reorder patch as
I'll post an add-on patch."12"
move_charge performance improbement patches will be posted later.
More information about the Containers