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

[Tom Talpey]

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:
> [...]
> > > > What I'd really like to see is to go back to the original fio parameters
> > > > (1 thread, 64 iodepth) and try to get a result that gets at least close
> > > > to the speced 200K IOPS of the NVMe device. There seems to be something
> > > > wrong with yours, currently.
> > >
> > > I'll dig into what has gone wrong with the test. I see fio putting data files
> > > in the right place, so the obvious "using the wrong drive" is (probably)
> > > not it. Even though it really feels like that sort of thing. We'll see.
> > >
> > > > Then of course, the result with the patched get_user_pages, and
> > > > compare whichever of IOPS or CPU% changes, and how much.
> > > >
> > > > If these are within a few percent, I agree it's good to go. If it's
> > > > roughly 25% like the result just above, that's a rocky road.
> > > >
> > > > I can try this after the holiday on some basic hardware and might
> > > > be able to scrounge up better. Can you post that github link?
> > >
> > > Here:
> > >
> > >  ÂÂÂ git@xxxxxxxxxx:johnhubbard/linux (branch: gup_dma_testing)
> >
> > 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.

Tom.

> > Say, that branch reports it has not had a commit since June 30. Is that
> > the right one? What about gup_dma_for_lpc_2018?
>
> That's the right branch, but the AuthorDate for the head commit (only) somehow
> got stuck in the past. I just now amended that patch with a new date and pushed
> it, so the head commit now shows Nov 27:
>
>     https://github.com/johnhubbard/linux/commits/gup_dma_testing
>
>
> The actual code is the same, though. (It is still based on Nov 19th's f2ce1065e767
> commit.)
>
>
> thanks,