lkml.org 
[lkml]   [2006]   [Feb]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 0/6] lightweight robust futexes: -V3 - Why in userspace?
On Thu, 16 Feb 2006, Arjan van de Ven wrote:

> On Thu, 2006-02-16 at 20:06 +0100, Esben Nielsen wrote:
> > I just jump into a thread somewhere to ask my question :-)
> >
> > Why does the list have to be in userspace?
>
> because it's faster ;)
>
>
Faster???
As I see it, extra manipulations have to be done even in the non-congested
case: Every time the lock is taken the locking thread has to add the lock
to a the list, and reversely remove the lock from the list. I.e.
instructions are _added_ to the fast path where you stay purely in
userspace.

I am ofcourse comparing to a solution where you do a syscall on everytime
you do a lock. What I am asking about is whethere it wouldn't be
enough to maintain the list at the FUTEX_WAIT/FUTEX_WAKE operation - i.e.
the slow path where you have to go into the kernel.

Esben


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-02-16 21:07    [W:0.106 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site