Re: 2.6.6-rc{1,2} bad VM/NFS interaction in case of dirty page writeback

Christoph Hellwig
2004-04-28T05:29:59Z

On Tue, Apr 27, 2004 at 11:36:47AM -0400, Trond Myklebust wrote:
> writepage() only deals with one page at a time, so it will work fine for
> doing stage 1.
> If you also try force it to do stage 2, then you will end up with chunks
> of size <= PAGE_CACHE_SIZE because there will only be 1 page on the NFS
> private list of dirty pages. In practice this again means that you
> usually have to send 8 times as many RPC requests to the server in order
> to process the same amount of data.

There's nothing speaking against probing for more dirty pages before and
after the one ->writepage wants to write out and send the big request
out. XFS does this to avoid creating small extents when converting from
delayed allocated space to real extents.