Hi Guys, On Fri, May 29, 2015 at 2:35 PM, Ming Lei <ming....@canonical.com> wrote: > Hi Guys, > > There are about 3 advantages to use direct I/O and AIO on > read/write loop's backing file: > > 1) double cache can be avoided, then memory usage gets > decreased a lot > > 2) not like user space direct I/O, there isn't cost of > pinning pages > > 3) avoid context switch for obtaining good throughput > - in buffered file read, random I/O throughput is often obtained > only if they are submitted concurrently from lots of tasks; but for > sequential I/O, most of times they can be hit from page cache, so > concurrent submissions often introduce unnecessary context switch > and can't improve throughput much. There was such discussion[1] > to use non-blocking I/O to improve the problem for application. > - with direct I/O and AIO, concurrent submissions can be > avoided and random read throughput can't be affected meantime > > So this patchset trys to improve loop via AIO, and about 45% memory > usage can be decreased, see detailed data in commit log of patch4, > also IO throughput isn't affected too. > > V4: > - add detailed commit log for 'use kthread_work' > - allow userspace(sysfs, losetup) to decide if dio/aio is > used as suggested by Christoph and Dave Chinner > - only use dio if the backing block device's min io size > is 512 as pointed by Dave Chinner & Christoph
Gentle ping, :-) > > V3: > - based on Al's iov_iter work and Christoph's kiocb changes > - use kthread_work > - introduce IOCB_DONT_DIRTY_PAGE flag > - set QUEUE_FLAG_NOMERGES for loop's request queue > V2: > - remove 'extra' parameter to aio_kernel_alloc() > - try to avoid memory allcation inside queue req callback > - introduce 'use_mq' sysfs file for enabling kernel aio or disabling > it > V1: > - link: > http://marc.info/?t=140803157700004&r=1&w=2 > - improve failure path in aio_kernel_submit() > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
