[lkml]   [2015]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC][PATCH 0/5] Optimize percpu-rwsem
On Tue, May 26, 2015 at 02:57:53PM -0700, Linus Torvalds wrote:

> Because that is another example of a complete failure of a locking
> primitive that was just too specialized to be worth it.

<notices stale include in fs/file_table.c and removes it>

FWIW, I hadn't really looked into stop_machine uses, but fs/locks.c one
is really not all that great - there we have a large trashcan of a list
(every file_lock on the system) and the only use of that list is /proc/locks
output generation. Sure, additions take this CPU's spinlock. And removals
take pretty much a random one - losing the timeslice and regaining it on
a different CPU is quite likely with the uses there.

Why do we need a global lock there, anyway? Why not hold only one for
the chain currently being traversed? Sure, we'll need to get and drop
them in ->next() that way; so what?

 \ /
  Last update: 2015-06-05 04:01    [W:0.482 / U:11.652 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site