Jens Axboe [off-list ref] wrote:

quoted

 Why you do see a difference is that when ->max_queued isn't valid, you
 end up block a lot more in get_request_wait() because cfq_may_queue will
 disallow you to queue a lot more than with the patch. Since other io
 schedulers don't have these sort of checks, they behave like CFQ does
 with the bug in blk_init_queue() fixed.

On Sun, Aug 29, 2004 at 01:59:17PM -0700, Andrew Morton wrote:

The changlog wasn't that detailed ;)
But yes, it's the large nr_requests which is tripping up swapout.  I'm
assuming that when a process exits with its anonymous memory still under
swap I/O we're forgetting to actually free the pages when the I/O
completes.  So we end up with a ton of zero-ref swapcache pages on the LRU.
I assume.   Something odd's happening, that's for sure.

Maybe we need to be checking for this in end_swap_bio_write() or
rotate_reclaimable_page()?


-- wli
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