On 05/14/2012 07:58 AM, ehrhardt@linux.vnet.ibm.com wrote:

From: Christian Ehrhardt<redacted>

Swap readahead works fine, but the I/O to disk is almost always done in page
size requests, despite the fact that readahead submits 1<<page-cluster pages
at a time.
On older kernels the old per device plugging behavior might have captured
this and merged the requests, but currently all comes down to much more I/Os
than required.

On a single device this might not be an issue, but as soon as a server runs
on shared san resources savin I/Os not only improves swapin throughput but
also provides a lower resource utilization.

Signed-off-by: Christian Ehrhardt<redacted>

Acked-by: Rik van Riel <redacted>

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