On 3/8/18 6:42 PM, Andrei Vagin wrote: > Direct I/O allows to not affect the write-back cache, this is > expected when a non-buffered mode is used. > > Async I/O allows to handle a few commands concurrently, so a target shows a > better perfomance: > > Mode: O_DSYNC Async: 1 > $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sda --runtime=20 --numjobs=2 > WRITE: bw=45.9MiB/s (48.1MB/s), 21.9MiB/s-23.0MiB/s (22.0MB/s-25.2MB/s), io=919MiB (963MB), run=20002-20020msec > > Mode: O_DSYNC Async: 0 > $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepth=64 --name=/dev/sdb --runtime=20 --numjobs=2 > WRITE: bw=1607KiB/s (1645kB/s), 802KiB/s-805KiB/s (821kB/s-824kB/s), io=31.8MiB (33.4MB), run=20280-20295msec > > Known issue: > > DIF (PI) emulation doesn't work when a target uses async I/O, because > DIF metadata is saved in a separate file, and it is another non-trivial > task how to synchronize writing in two files, so that a following read > operation always returns a consisten metadata for a specified block. > > Cc: "Nicholas A. Bellinger" <nab@xxxxxxxxxxxxxxx> > Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx> > --- > drivers/target/target_core_file.c | 124 ++++++++++++++++++++++++++++++++++++-- > drivers/target/target_core_file.h | 1 + > 2 files changed, 120 insertions(+), 5 deletions(-) > > Tested-by: Bryant G. Ly <bryantly@xxxxxxxxxxxxxxxxxx> Patch looks good to me - Thanks for the performance enhancement! Btw I have been running I/O tests with HTX against this patch for 24 hrs and have no problems. -Bryant
