lkml.org 
[lkml]   [2008]   [May]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: POHMELFS high performance network filesystem. Transactions, failover, performance.
On Wed, 14 May 2008 06:41:53 -0700 (PDT) Sage Weil <sage@newdream.net> wrote:

> > On Wed, May 14, 2008 at 11:40:28AM +0400, Evgeniy Polyakov (johnpol@2ka.mipt.ru) wrote:
> > > > If any thread takes more than one kmap() at a time, it is deadlockable.
> > > > Because there is a finite pool of kmaps. Everyone can end up holding
> > > > one or more kmaps, then waiting for someone else to release one.
> > >
> > > It never takes the whole LAST_PKMAP maps. So the same can be applied to
> > > any user who kmaps at least one page - while user waits for free slot,
> > > it can be reused by someone else and so on.
> >
> > Actually CIFS uses the same logic: maps multiple pages in wrteback path
> > and release them after received reply.
>
> Yes. Only a pagevec at a time, though... apparently 14 is a small enough
> number not to bite too many people in practice?
>

In practice you need a large number of threads performing writeout to
trigger this. iirc that's how it was demonstrated back in the 2.4
days. Say, thousands of processes/threads doing write+fsync to
separate files.



\
 
 \ /
  Last update: 2008-05-14 20:13    [W:0.071 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site