lkml.org 
[lkml]   [2016]   [Oct]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] mm: vmalloc: Replace purge_lock spinlock with atomic refcount
On Sat, 15 Oct 2016 03:42:42 -0700
Joel Fernandes <joelaf@google.com> wrote:

> The purge_lock spinlock causes high latencies with non RT kernel. This has been
> reported multiple times on lkml [1] [2] and affects applications like audio.
>
> In this patch, I replace the spinlock with an atomic refcount so that
> preemption is kept turned on during purge. This Ok to do since [3] builds the
> lazy free list in advance and atomically retrieves the list so any instance of
> purge will have its own list it is purging. Since the individual vmap area
> frees are themselves protected by a lock, this is Ok.

This is a good idea, and good results, but that's not what the spinlock was
for -- it was for enforcing the sync semantics.

Going this route, you'll have to audit callers to expect changed behavior
and change documentation of sync parameter.

I suspect a better approach would be to instead use a mutex for this, and
require that all sync=1 callers be able to sleep. I would say that most
probably already can.

Thanks,
Nick

\
 
 \ /
  Last update: 2016-10-17 06:00    [W:0.053 / U:1.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site