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Subject: Re: [PATCH v2 0/6] RFC: gup+dma: tracking dma-pinned pages
To:     Tom Talpey <tom@talpey.com>, <john.hubbard@gmail.com>,
        <linux-mm@kvack.org>
CC:     Andrew Morton <akpm@linux-foundation.org>,
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From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <7a68b7fc-ff9d-381e-2444-909c9c2f6679@nvidia.com>
Date:   Thu, 29 Nov 2018 17:39:06 -0800
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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.

Continuing on, then: running a before and after test, I don't see any significant 
difference in the fio results:

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:

$ 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%

---------------------------------------------------------
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,
-- 
John Hubbard
NVIDIA