On 12/14/12 17:44, scameron@xxxxxxxxxxxxxxxxxx wrote:
I expect the flash devices re-order requests as well, simply because to feed requests to the things at a sufficient rate, you have to pump requests into them concurrently on multiple hardware queues -- a single cpu jamming requests into them as fast as it can is still not fast enough to keep them busy. Consequently, they *can't* care about ordering, as the relative order requests on different hardware queues are submitted into them is not even really controlled, so the OS *can't* count on concurrent requests not to be essentially "re-ordered", just because of the nature of the way requests get into the device.
Why should a flash device have to reorder write requests ? These devices typically use a log-structured file system internally.
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