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SubjectRe: [PATCH] Prevent large file writeback starvation
On Mon, Feb 06, 2006 at 03:14:35PM -0800, Andrew Morton wrote:
>
> So to fix both these problems we need to be smarter about terminating the
> wb_kupdate() loop. Something like "loop until no expired inodes have been
> written".
>
> Wildly untested patch:

> wbc.nr_to_write = MAX_WRITEBACK_PAGES;
> + wbc.wrote_expired_inode = 0;
> writeback_inodes(&wbc);
> - if (wbc.nr_to_write > 0) {
> + if (wbc.wrote_expired_inode == 0) {
> if (wbc.encountered_congestion)
> blk_congestion_wait(WRITE, HZ/10);
> else

FWIW, Theres a problem with the logic here - if we've encountered congestion,
we want to wait even if we wrote back expired inodes. Should it be:

if (!wbc.wrote_expired_inode && !wbc.encountered_congestion)
break; /* All the old data is written */
if (wbc.encountered_congestion)
blk_congestion_wait(WRITE, HZ/10);

Cheers,

Dave.
--
Dave Chinner
R&D Software Enginner
SGI Australian Software Group
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