lkml.org 
[lkml]   [2017]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] list_lru: Prefetch neighboring list entries before acquiring lock
On Wed 29-11-17 09:17:34, Waiman Long wrote:
> The list_lru_del() function removes the given item from the LRU list.
> The operation looks simple, but it involves writing into the cachelines
> of the two neighboring list entries in order to get the deletion done.
> That can take a while if the cachelines aren't there yet, thus
> prolonging the lock hold time.
>
> To reduce the lock hold time, the cachelines of the two neighboring
> list entries are now prefetched before acquiring the list_lru_node's
> lock.
>
> Using a multi-threaded test program that created a large number
> of dentries and then killed them, the execution time was reduced
> from 38.5s to 36.6s after applying the patch on a 2-socket 36-core
> 72-thread x86-64 system.
>
> Signed-off-by: Waiman Long <longman@redhat.com>

The patch still seems to be in the mmotm tree while it breaks
compilation. At least m32r defconfig complains with
mm/list_lru.c: In function 'list_lru_del':
mm/list_lru.c:141:2: error: implicit declaration of function 'prefetchw' [-Werror=implicit-function-declaration]
prefetchw(item->prev);

It also seems that there is no general agreement in the patch. Andrew,
do you plan to keep it?
--
Michal Hocko
SUSE Labs

\
 
 \ /
  Last update: 2017-12-05 15:50    [W:0.125 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site