On 08/27/2012 12:00 AM, Shaohua Li wrote:
The swapin readahead does a blind readahead regardless if the swapin is sequential. This is ok for harddisk and random read, because read big size has no penality in harddisk, and if the readahead pages are garbage, they can be reclaimed fastly. But for SSD, big size read is more expensive than small size read. If readahead pages are garbage, such readahead only has overhead. This patch addes a simple random read detection like what file mmap readahead does. If random read is detected, swapin readahead will be skipped. This improves a lot for a swap workload with random IO in a fast SSD. I run anonymous mmap write micro benchmark, which will triger swapin/swapout. runtime changes with path randwrite harddisk -38.7% seqwrite harddisk -1.1% randwrite SSD -46.9% seqwrite SSD +0.3% For both harddisk and SSD, the randwrite swap workload run time is reduced significant. sequential write swap workload hasn't chanage.
Very nice results!
Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx> -- All rights reversed -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>