Re: [PATCH 29/35] nfs: in-commit pages accounting and wait queue

Trond Myklebust
2010-12-13T21:15:56Z

On Mon, 2010-12-13 at 22:47 +0800, Wu Fengguang wrote:
> plain text document attachment (writeback-nfs-in-commit.patch)
> When doing 10+ concurrent dd's, I observed very bumpy commits submission
> (partly because the dd's are started at the same time, and hence reached
> 4MB to-commit pages at the same time). Basically we rely on the server
> to complete and return write/commit requests, and want both to progress
> smoothly and not consume too many pages. The write request wait queue is
> not enough as it's mainly network bounded. So add another commit request
> wait queue. Only async writes need to sleep on this queue.
>

I'm not understanding the above reasoning. Why should we serialise
commits at the per-filesystem level (and only for non-blocking flushes
at that)?

Cheers
Trond
--
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com