On Fri, Aug 15, 2014 at 12:53 AM, Jens Axboe <axboe@xxxxxxxxx> wrote: > On 08/14/2014 09:50 AM, Ming Lei wrote: >> Hi, >> >> The 1st two patches introduce kernel AIO support, most of >> is borrowed from Dave's work last year, and thanks to ITER_BVEC, >> it is much simper to implement kernel AIO now. AIO model >> is quite suitable for implementing kernel stuff, and can >> help improve both throughput and CPU utilization. Lots of >> kernel components should benefit from it, such as: >> - loop driver, >> - all kinds of kernel I/O target driver(SCSI, USB storage >> or UAS, ...) >> - kernel socket users might benefit from it too if socket >> AIO is mature >> >> The following 6 patches convert current loop driver into blk-mq: >> - loop's scalability gets improved much >> - loop driver gets quite simplified, and the conversion can >> be throught as cleanup too >> >> The 9th patch uses kernel AIO with O_DIRECT to improve loop's >> performance in single job situation, and avoid double cache >> issue for loop driver too. >> >> With the change, loop block's performance can be doubled in my >> fio test(randread, single job, libaio). If more fio jobs are used, >> the throughput can be improved much more because of blk-mq. >> >> Given loop is used quite widely, especially in VM environment, >> also the change is quite small, hope it can be merged finally. > > Looks pretty damn good to me, even the kernel aio bits are nice and > simple. Do you have any numbers on loop performance before and after the > blk-mq conversion? Just curious. Your concern is right, previous I thought that mq conversion wouldn't improve throughput, but I did ignore workqueue's concurrency management, it turns out blk-mq conversion can improvment throughput close to 10 times in my test(loop over virtio-blk which is backed by one image on SSD). It is like POSIX style AIO after mq conversion thanks to workqueue, and I need to update the performance data in V2. Actually kernel AIO needn't such high concurrency. Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
