order of I/O
Posted Apr 16, 2004 22:53 UTC (Fri) by giraffedata
Parent article: VM changes in 2.6.6
As a result of the changes, the order in which dirty pages are written to disk has changed; writing always happens in file-offset order now.
I find that hard to believe. The order in which pages are written to disk is controlled by the block layer/device driver, and tends to be disk address order. I presume this means to say the order in which the I/Os to write dirty pages to disk are requested of the block layer always happens in file-offset order (as opposed to order in which they became dirty) now. It's hard to see how that makes a big difference in performance, considering I/Os to clean all the dirty pages are requested at about the same time.
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