K 10
svn:author
V 5
markj
K 8
svn:date
V 27
2016-03-14T22:26:06.272418Z
K 7
svn:log
V 855
Decrement maxscan by the number of clustered pages.

This helps ensure that pages in the laundry queue are not examined more
than once during a scan. However, because pages are not removed from the
queue until they have been laundered (i.e., the pageout I/O completes), this
could cause the scan to stop before it has reached the end of the queue.
Thus, dequeue all clustered pages before passing them to the pager. This
moves some work out of the completion handler, which is usually invoked
asynchronously. In a benchmark where multiple threads sequentially write
to MAP_NOSYNC-mapped files, this change has no significant effect on
runtime but reduces contention on the laundry queue lock (as measured with
lockstat -e 0). Note however that this represents only a very small
fraction of the total lock contention in the benchmark.

Discussed with:	alc

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