It would be useful to post some details about your test hardware (eg. HDD vs. SSD, CPU cores+speed, RAM), so that it is possible to make a good comparison of someone sees different results. Cheers, Andreas > On Jul 25, 2019, at 19:12, Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> wrote: > > > >> On 19/7/26 05:20, Andreas Dilger wrote: >> >>> On Jul 23, 2019, at 5:17 AM, Joseph Qi <jiangqi903@xxxxxxxxx> wrote: >>> >>> Hi Ted & Jan, >>> Could you please give your valuable comments? >> >> It seems like the original patches should be reverted? There is no data > > From my test result, yes. > I've also tested libaio with iodepth 16, it behaves the same. Here is the test > data for libaio 4k randrw: > > ------------------------------------------------------------------------------------------- > w/ parallel dio reads | READ 78313KB/s, 19578, 1698.70us | WRITE 78313KB/s, 19578, 4837.60us > ------------------------------------------------------------------------------------------- > w/o parallel dio reads| READ 387774KB/s, 96943, 1009.73us | WRITE 387656KB/s，96914, 308.87us > ------------------------------------------------------------------------------------------- > > Since this commit went into upstream long time ago，to be precise, Linux > 4.9, I wonder if someone else has also observed this regression, or > anything I missed? > > Thanks, > Joseph > >> in the original commit message that indicates there is an actual performance >> improvement from that patch, but there is data here showing it hurts both >> read and write performance quite significantly. >>> Cheers, Andreas >> >>>> On 19/7/19 17:22, Joseph Qi wrote: >>>> Hi Ted & Jan, >>>> I've observed an significant performance regression with the following >>>> commit in my Intel P3600 NVMe SSD. >>>> 16c54688592c ext4: Allow parallel DIO reads >>>> >>>> From my initial investigation, it may be because of the >>>> inode_lock_shared (down_read) consumes more than inode_lock (down_write) >>>> in mixed random read write workload. >>>> >>>> Here is my test result. >>>> >>>> ioengine=psync >>>> direct=1 >>>> rw=randrw >>>> iodepth=1 >>>> numjobs=8 >>>> size=20G >>>> runtime=600 >>>> >>>> w/ parallel dio reads : kernel 5.2.0 >>>> w/o parallel dio reads: kernel 5.2.0, then revert the following commits: >>>> 1d39834fba99 ext4: remove EXT4_STATE_DIOREAD_LOCK flag (related) >>>> e5465795cac4 ext4: fix off-by-one error when writing back pages before dio read (related) >>>> 16c54688592c ext4: Allow parallel DIO reads >>>> >>>> bs=4k: >>>> ------------------------------------------------------------------------------------------- >>>> w/ parallel dio reads | READ 30898KB/s, 7724, 555.00us | WRITE 30875KB/s, 7718, 479.70us >>>> ------------------------------------------------------------------------------------------- >>>> w/o parallel dio reads| READ 117915KB/s, 29478, 248.18us | WRITE 117854KB/s，29463, 21.91us >>>> ------------------------------------------------------------------------------------------- >>>> >>>> bs=16k: >>>> ------------------------------------------------------------------------------------------- >>>> w/ parallel dio reads | READ 58961KB/s, 3685, 835.28us | WRITE 58877KB/s, 3679, 1335.98us >>>> ------------------------------------------------------------------------------------------- >>>> w/o parallel dio reads| READ 218409KB/s, 13650, 554.46us | WRITE 218257KB/s，13641, 29.22us >>>> ------------------------------------------------------------------------------------------- >>>> >>>> bs=64k: >>>> ------------------------------------------------------------------------------------------- >>>> w/ parallel dio reads | READ 119396KB/s, 1865, 1759.38us | WRITE 119159KB/s, 1861, 2532.26us >>>> ------------------------------------------------------------------------------------------- >>>> w/o parallel dio reads| READ 422815KB/s, 6606, 1146.05us | WRITE 421619KB/s, 6587, 60.72us >>>> ------------------------------------------------------------------------------------------- >>>> >>>> bs=512k: >>>> ------------------------------------------------------------------------------------------- >>>> w/ parallel dio reads | READ 392973KB/s, 767, 5046.35us | WRITE 393165KB/s, 767, 5359.86us >>>> ------------------------------------------------------------------------------------------- >>>> w/o parallel dio reads| READ 590266KB/s, 1152, 4312.01us | WRITE 590554KB/s, 1153, 2606.82us >>>> ------------------------------------------------------------------------------------------- >>>> >>>> bs=1M: >>>> ------------------------------------------------------------------------------------------- >>>> w/ parallel dio reads | READ 487779KB/s, 476, 8058.55us | WRITE 485592KB/s, 474, 8630.51us >>>> ------------------------------------------------------------------------------------------- >>>> w/o parallel dio reads| READ 593927KB/s, 580, 7623.63us | WRITE 591265KB/s, 577, 6163.42us >>>> ------------------------------------------------------------------------------------------- >>>> >>>> Thanks, >>>> Joseph >>>> >> >> >> Cheers, Andreas >> >> >> >> >>
