Re: apparmor: global buffers spin lock may get contended

[John Johansen]

On 10/30/22 20:52, Sergey Senozhatsky wrote:
> On (22/10/28 02:34), John Johansen wrote:
> >  From d026988196fdbda7234fb87bc3e4aea22edcbaf9 Mon Sep 17 00:00:00 2001
> > From: John Johansen <john.johansen@xxxxxxxxxxxxx>
> > Date: Tue, 25 Oct 2022 01:18:41 -0700
> > Subject: [PATCH] apparmor: cache buffers on percpu list if there is lock
> >   contention
> >
> > On a heavily loaded machine there can be lock contention on the
> > global buffers lock. Add a percpu list to cache buffers on when
> > lock contention is encountered.
> >
> > When allocating buffers attempt to use cached buffers first,
> > before taking the global buffers lock. When freeing buffers
> > try to put them back to the global list but if contention is
> > encountered, put the buffer on the percpu list.
> >
> > The length of time a buffer is held on the percpu list is dynamically
> > adjusted based on lock contention.  The amount of hold time is rapidly
> > increased and slow ramped down.
> >
> > Signed-off-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
>
> Reported-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>

yep, thanks for catching that