[LU-4198] Improve IO performance when using DIRECT IO using libaio

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.14.0
• Affects Version/s: Lustre 2.4.1
• Labels: clio
• Environment: Seen in two environments. AWS cloud (Robert R.) and a dual-OSS setup (3 SSD per OST) over 2x10 GbE.
• Severity: 3
• Assignee: Zhenyu Xu
• Reporter: Brett Lee (Inactive)

Description

Attached to this Jira are some numbers from the direct IO tests. Write operations only.

It was noticed that setting RPCs in flight to 256 in these tests gives poorer performance. max rpc here is set to 32.

• A sample FIO output:

  fio.4k.write.1.23499: (g=0): rw=write, bs=4K-4K/4K-4K/4K-4K, ioengine=sync, iodepth=1
  fio-2.1.2
  Starting 1 process
  fio.4k.write.1.23499: Laying out IO file(s) (1 file(s) / 10MB)
  
  fio.4k.write.1.23499: (groupid=0, jobs=1): err= 0: pid=10709: Fri Nov  1 11:47:29 2013
    write: io=10240KB, bw=2619.7KB/s, iops=654, runt=  3909msec
      clat (usec): min=579, max=5283, avg=1520.43, stdev=1216.20
       lat (usec): min=580, max=5299, avg=1521.37, stdev=1216.22
      clat percentiles (usec):
       |  1.00th=[  604],  5.00th=[  652], 10.00th=[  668], 20.00th=[  708],
       | 30.00th=[  732], 40.00th=[  756], 50.00th=[  796], 60.00th=[  844],
       | 70.00th=[ 1320], 80.00th=[ 3440], 90.00th=[ 3568], 95.00th=[ 3632],
       | 99.00th=[ 3824], 99.50th=[ 5024], 99.90th=[ 5216], 99.95th=[ 5280],
       | 99.99th=[ 5280]
      bw (KB  /s): min= 1224, max= 4366, per=97.64%, avg=2557.14, stdev=1375.64
      lat (usec) : 750=37.50%, 1000=30.12%
      lat (msec) : 2=5.00%, 4=26.76%, 10=0.62%
    cpu          : usr=0.92%, sys=8.70%, ctx=2562, majf=0, minf=25
    IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
       submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
       complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
       issued    : total=r=0/w=2560/d=0, short=r=0/w=0/d=0
  
  Run status group 0 (all jobs):
    WRITE: io=10240KB, aggrb=2619KB/s, minb=2619KB/s, maxb=2619KB/s, mint=3909msec, maxt=3909msec
  

Issue Links

• is duplicated by: LU-13786 Take server-side locks for direct i/o
• is related to: LU-13900 don't call aio_complete() in lustre upon errors
• is related to: LU-247 Lustre client slow performance on BG/P IONs: unaligned DIRECT_IO
• is related to: LU-13697 short io for AIO
• is related to: LU-9409 Lustre small IO write performance improvement
• is related to: LU-10278 lfs migrate: make use of direct i/o optional
• is related to: LU-13801 Enable io_uring interface for Lustre client
• is related to: LU-12687 Fast ENOSPC on direct I/O
• is related to: LU-13798 Improve direct i/o performance with multiple stripes: Submit all stripes of a DIO and then wait

Comments

[Jinshan Xiong (Inactive)]

This work is still useful so probably we should keep this ticket open.

[Patrick Farrell (Inactive)]

Jinshan,

Attached patch is a suggestion for fixing the need for size glimpsing for dio reads. Not 100% sure it's safe, but some local testing suggests it's OK. (Diff was a little big to drop in gerrit)

[Patrick Farrell (Inactive)]

LU-247 is pretty old and probably no one has time to update it... But it could be very useful (with this) for improving < page size write performance.

[Patrick Farrell (Inactive)]

Patch is still in flight. (Hope this is OK.)

[Robert Read]

[Jinshan Xiong (Inactive)]

Let's reopen this ticket after we have a more convincible solution for this issue.

[Andreas Dilger]

Patches in Gerrit for this issue:
http://review.whamcloud.com/8201
http://review.whamcloud.com/8612

[Richard Henwood (Inactive)]

This ticket isn't directly related to CLIO Simplification work. The ticket relationships on Jira have been updated to reflect this.

[Richard Henwood (Inactive)]

Jinshan, please update this ticket description to include the reason that this ticket is a dependency for LU-3259.

[Brett Lee (Inactive)]

Jinshan - an OST failed on me (each OST is one SATA-II or III disk) and have no other suitable disks. Have ordered a pair of WD 10K RPM Velociraptors (200 MB/s) that will support queue depth up to 32 (NCQ). On hold till then.

[Brett Lee (Inactive)]

Better? I thought those results were pretty good already. Will give it a try.