lkml.org 
[lkml]   [2018]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/2] rcu: Transform kfree_rcu() into kvfree_rcu()
On Wed, Feb 07, 2018 at 05:45:13PM +0100, Jesper Dangaard Brouer wrote:
> On Wed, 7 Feb 2018 08:57:00 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> > To me kvfree() is a special case and should not be used by RCU as a
> > generic function. That would make RCU and MM much more coupled than
> > necessary.
>
> For the record, I fully agree with Steve here.
>
> And being a performance "fanatic" I don't like to have the extra branch
> (and compares) in the free code path... but it's a MM-decision (and
> sometimes you should not listen to "fanatics" ;-))

While free_rcu() is not withut its performance requirements, I think it's
currently dominated by cache misses and not by branches. By the time RCU
gets to run callbacks, memory is certainly L1/L2 cache-cold and probably
L3 cache-cold. Also calling the callback functions is utterly impossible
for the branch predictor.

\
 
 \ /
  Last update: 2018-02-07 19:11    [W:0.080 / U:29.912 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site