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由 Michael Lyle 提交于
Writeback keys are presently iterated and dispatched for writeback in order of the logical block address on the backing device. Multiple may be, in parallel, read from the cache device and then written back (especially when there are contiguous I/O). However-- there was no guarantee with the existing code that the writes would be issued in LBA order, as the reads from the cache device are often re-ordered. In turn, when writing back quickly, the backing disk often has to seek backwards-- this slows writeback and increases utilization. This patch introduces an ordering mechanism that guarantees that the original order of issue is maintained for the write portion of the I/O. Performance for writeback is significantly improved when there are multiple contiguous keys or high writeback rates. Signed-off-by: NMichael Lyle <mlyle@lyle.org> Reviewed-by: NTang Junhui <tang.junhui@zte.com.cn> Tested-by: NTang Junhui <tang.junhui@zte.com.cn> Signed-off-by: NJens Axboe <axboe@kernel.dk>
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