lkml.org 
[lkml]   [2013]   [Sep]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 0/2 v2] dcache: get/release read lock in read_seqbegin_or_lock() & friend
From
On Thu, Sep 12, 2013 at 9:38 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Thu, Sep 12, 2013 at 7:55 AM, Waiman Long <Waiman.Long@hp.com> wrote:
>> Change log
>> ----------
>> v1->v2:
>> - Rename the new seqlock primitives to read_seqexcl_lock* and
>> read_seqexcl_unlock*.
>
> Applied.

Btw, when I tried to benchmark this, I failed miserably.

Why?

If you do a threaded benchmark of "getcwd()", you end up spending all
your time in a spinlock anyway: get_fs_root_and_pwd() takes the
fs->lock to get the root/pwd.

Now, AIM7 probably uses processes, not threads, so you don't see this,
and maybe I shouldn't care. But looking at it, it annoys me
enormously, because the whole get_fs_root_and_pwd() is just stupid.

Putting it all under the RCU lock and then changing it to use
get_fs_root_and_pwd_rcu() that just uses the fs->seq sequence
read-lock looks absolutely trivial.

Linus


\
 
 \ /
  Last update: 2013-09-12 20:01    [W:0.085 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site