Re: [PATCH v2 0/6] RFC: gup+dma: tracking dma-pinned pages

[John Hubbard <jhubbard@nvidia.com>]

On 11/29/18 6:18 PM, Tom Talpey wrote:
> On 11/29/2018 8:39 PM, John Hubbard wrote:
>> On 11/28/18 5:59 AM, Tom Talpey wrote:
>>> On 11/27/2018 9:52 PM, John Hubbard wrote:
>>>> On 11/27/18 5:21 PM, Tom Talpey wrote:
>>>>> On 11/21/2018 5:06 PM, John Hubbard wrote:
>>>>>> On 11/21/18 8:49 AM, Tom Talpey wrote:
>>>>>>> On 11/21/2018 1:09 AM, John Hubbard wrote:
>>>>>>>> On 11/19/18 10:57 AM, Tom Talpey wrote:
>>>> [...]
>>>>> I'm super-limited here this week hardware-wise and have not been able
>>>>> to try testing with the patched kernel.
>>>>>
>>>>> I was able to compare my earlier quick test with a Bionic 4.15 kernel
>>>>> (400K IOPS) against a similar 4.20rc3 kernel, and the rate dropped to
>>>>> ~_375K_ IOPS. Which I found perhaps troubling. But it was only a quick
>>>>> test, and without your change.
>>>>>
>>>>
>>>> So just to double check (again): you are running fio with these parameters,
>>>> right?
>>>>
>>>> [reader]
>>>> direct=1
>>>> ioengine=libaio
>>>> blocksize=4096
>>>> size=1g
>>>> numjobs=1
>>>> rw=read
>>>> iodepth=64
>>>
>>> Correct, I copy/pasted these directly. I also ran with size=10g because
>>> the 1g provides a really small sample set.
>>>
>>> There was one other difference, your results indicated fio 3.3 was used.
>>> My Bionic install has fio 3.1. I don't find that relevant because our
>>> goal is to compare before/after, which I haven't done yet.
>>>
>>
>> OK, the 50 MB/s was due to my particular .config. I had some expensive debug options
>> set in mm, fs and locking subsystems. Turning those off, I'm back up to the rated
>> speed of the Samsung NVMe device, so now we should have a clearer picture of the
>> performance that real users will see.
> 
> Oh, good! I'm especially glad because I was having a heck of a time
> reconfiguring the one machine I have available for this.
> 
>> Continuing on, then: running a before and after test, I don't see any significant
>> difference in the fio results:
> 
> Excerpting from below:
> 
>> Baseline 4.20.0-rc3 (commit f2ce1065e767), as before:
>>     read: IOPS=193k, BW=753MiB/s (790MB/s)(1024MiB/1360msec)
>>    cpu          : usr=16.26%, sys=48.05%, ctx=251258, majf=0, minf=73
> 
> vs
> 
>> With patches applied:
>>     read: IOPS=193k, BW=753MiB/s (790MB/s)(1024MiB/1360msec)
>>    cpu          : usr=16.26%, sys=48.05%, ctx=251258, majf=0, minf=73
> 
> Perfect results, not CPU limited, and full IOPS.
> 
> Curiously identical, so I trust you've checked that you measured
> both targets, but if so, I say it's good.
> 

Argh, copy-paste error in the email. The real "before" is ever so slightly
better, at 194K IOPS and 759 MB/s:

 $ fio ./experimental-fio.conf
reader: (g=0): rw=read, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=64
fio-3.3
Starting 1 process
Jobs: 1 (f=1)
reader: (groupid=0, jobs=1): err= 0: pid=1715: Thu Nov 29 17:07:09 2018
   read: IOPS=194k, BW=759MiB/s (795MB/s)(1024MiB/1350msec)
    slat (nsec): min=1245, max=2812.7k, avg=1538.03, stdev=5519.61
    clat (usec): min=148, max=755, avg=326.85, stdev=18.13
     lat (usec): min=150, max=3483, avg=328.41, stdev=19.53
    clat percentiles (usec):
     |  1.00th=[  322],  5.00th=[  326], 10.00th=[  326], 20.00th=[  326],
     | 30.00th=[  326], 40.00th=[  326], 50.00th=[  326], 60.00th=[  326],
     | 70.00th=[  326], 80.00th=[  326], 90.00th=[  326], 95.00th=[  326],
     | 99.00th=[  355], 99.50th=[  537], 99.90th=[  553], 99.95th=[  553],
     | 99.99th=[  619]
   bw (  KiB/s): min=767816, max=783096, per=99.84%, avg=775456.00, stdev=10804.59, samples=2
   iops        : min=191954, max=195774, avg=193864.00, stdev=2701.15, samples=2
  lat (usec)   : 250=0.09%, 500=99.30%, 750=0.61%, 1000=0.01%
  cpu          : usr=18.24%, sys=44.77%, ctx=251527, majf=0, minf=73
  IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
     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=0.1%, >=64=0.0%
     issued rwts: total=262144,0,0,0 short=0,0,0,0 dropped=0,0,0,0
     latency   : target=0, window=0, percentile=100.00%, depth=64

Run status group 0 (all jobs):
   READ: bw=759MiB/s (795MB/s), 759MiB/s-759MiB/s (795MB/s-795MB/s), io=1024MiB (1074MB), run=1350-1350msec

Disk stats (read/write):
  nvme0n1: ios=222853/0, merge=0/0, ticks=71410/0, in_queue=71935, util=100.00%

thanks,
-- 
John Hubbard
NVIDIA
> 
>>
>> fio.conf:
>>
>> [reader]
>> direct=1
>> ioengine=libaio
>> blocksize=4096
>> size=1g
>> numjobs=1
>> rw=read
>> iodepth=64
>>
>> ---------------------------------------------------------
>> Baseline 4.20.0-rc3 (commit f2ce1065e767), as before:
>>
[deleted with prejudice. See the correction above, instead] --jhubbard
>>
>> ---------------------------------------------------------
>> With patches applied:
>>
>> <redforge> fast_256GB $ fio ./experimental-fio.conf
>> reader: (g=0): rw=read, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=64
>> fio-3.3
>> Starting 1 process
>> Jobs: 1 (f=1)
>> reader: (groupid=0, jobs=1): err= 0: pid=1738: Thu Nov 29 17:20:07 2018
>>     read: IOPS=193k, BW=753MiB/s (790MB/s)(1024MiB/1360msec)
>>      slat (nsec): min=1381, max=46469, avg=1649.48, stdev=594.46
>>      clat (usec): min=162, max=12247, avg=330.00, stdev=185.55
>>       lat (usec): min=165, max=12253, avg=331.68, stdev=185.69
>>      clat percentiles (usec):
>>       |  1.00th=[  322],  5.00th=[  326], 10.00th=[  326], 20.00th=[  326],
>>       | 30.00th=[  326], 40.00th=[  326], 50.00th=[  326], 60.00th=[  326],
>>       | 70.00th=[  326], 80.00th=[  326], 90.00th=[  326], 95.00th=[  326],
>>       | 99.00th=[  379], 99.50th=[  594], 99.90th=[  603], 99.95th=[  611],
>>       | 99.99th=[12125]
>>     bw (  KiB/s): min=751640, max=782912, per=99.52%, avg=767276.00, stdev=22112.64, samples=2
>>     iops        : min=187910, max=195728, avg=191819.00, stdev=5528.16, samples=2
>>    lat (usec)   : 250=0.08%, 500=99.30%, 750=0.59%
>>    lat (msec)   : 20=0.02%
>>    cpu          : usr=16.26%, sys=48.05%, ctx=251258, majf=0, minf=73
>>    IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0%
>>       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=0.1%, >=64=0.0%
>>       issued rwts: total=262144,0,0,0 short=0,0,0,0 dropped=0,0,0,0
>>       latency   : target=0, window=0, percentile=100.00%, depth=64
>>
>> Run status group 0 (all jobs):
>>     READ: bw=753MiB/s (790MB/s), 753MiB/s-753MiB/s (790MB/s-790MB/s), io=1024MiB (1074MB), run=1360-1360msec
>>
>> Disk stats (read/write):
>>    nvme0n1: ios=220798/0, merge=0/0, ticks=71481/0, in_queue=71966, util=100.00%
>>
>>
>> thanks,
>>
>