[lkml]   [2007]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] nfs: fix congestion control
On Tue, 2007-01-16 at 17:27 -0500, Trond Myklebust wrote:
> On Tue, 2007-01-16 at 23:08 +0100, Peter Zijlstra wrote:
> > Subject: nfs: fix congestion control
> >
> > The current NFS client congestion logic is severely broken, it marks the
> > backing device congested during each nfs_writepages() call and implements
> > its own waitqueue.
> >
> > Replace this by a more regular congestion implementation that puts a cap
> > on the number of active writeback pages and uses the bdi congestion waitqueue.
> >
> > NFSv[34] commit pages are allowed to go unchecked as long as we are under
> > the dirty page limit and not in direct reclaim.

> What on earth is the point of adding congestion control to COMMIT?
> Strongly NACKed.

They are dirty pages, how are we getting rid of them when we reached the
dirty limit?

> Why 16MB of on-the-wire data? Why not 32, or 128, or ...

Andrew always promotes a fixed number for congestion control, I pulled
one from a dark place. I have no problem with a more dynamic solution.

> Solaris already allows you to send 2MB of write data in a single RPC
> request, and the RPC engine has for some time allowed you to tune the
> number of simultaneous RPC requests you have on the wire: Chuck has
> already shown that read/write performance is greatly improved by upping
> that value to 64 or more in the case of RPC over TCP. Why are we then
> suddenly telling people that they are limited to 8 simultaneous writes?

min(max RPC size * max concurrent RPC reqs, dirty threshold) then?

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-01-17 05:53    [W:0.087 / U:4.404 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site