On Thu, Jul 16, 2015 at 11:37 AM, 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. > > V7: > - only 4/6 and 5/6 updated > - update direct io after lo->offset is changed(4/6) > - fix updating LO_FLAGS_DIRECT_IO in __loop_update_dio()(4/6) > - introduce ioctl cmd of LOOP_SET_DIRECT_IO(5/6) for case of > 'mount -o loop' > - losetup git tree: > > http://kernel.ubuntu.com/git/ming/util-linux.git/log/?h=loop-dio-v7 > - how to set direct io > losetup --direct-io 1 /dev/loopN > - how to clear direct io > losetup --direct-io 0 /dev/loopN > - how to show if direct io is used for accessing backing file > losetup -l > V6: > - only patch 4 and patch 5 get updated > - check lo->lo_offset to decide if direct IO can be supported(4/5) > - introduce one flag for userspace(losetup) to keep updated > if using direct I/O to access backing file(4/5) > - implement patches for util-linux(losetup) so that losetup can > enable direct I/O feature:(4/5) > > http://kernel.ubuntu.com/git/ming/util-linux.git/log/?h=losetup-dio > > - remove the direct IO control interface from sysfs(4/5) > - handle partial read in case of direct read (5/5) > - add more comments for direct IO (5/5) > V5: > - don't introduce IOCB_DONT_DIRTY_PAGE and bypass dirtying > for ITER_KVEC and ITER_BVEC direct IO(read), as required by > Christoph > > 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 > 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() > > drivers/block/loop.c | 263 > ++++++++++++++++++++++++++++++++++++---------- > drivers/block/loop.h | 13 +-- > fs/direct-io.c | 9 +- > include/uapi/linux/loop.h | 2 + > 4 files changed, 221 insertions(+), 66 deletions(-)
Hi Guys, Gentle ping. thanks, -- 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/
