On Wed, Dec 11, 2019 at 5:11 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>
> 15K is likely too slow to really show an issue, I'm afraid. The 970
> is no slouch, but your crypt setup will likely hamper it a lot. You
> don't have a non-encrypted partition on it?
No. I normally don't need all that much disk, so I've never upgraded
my ssd from the 512G size.
Which means that it's actually half full or so, and I never felt like
"I should keep an unencrypted partition for IO testing", since I don't
generally _do_ any IO testing.
I can get my load up with "numjobs=8" and get my iops up to the 100k
range, though.
But kswapd doesn't much seem to care, the CPU percentage actually does
_down_ to 0.39% when I try that. Probably simply because now my CPU's
are busy, so they are running at 4.7Ghz instead of the 800Mhz "mostly
idle" state ...
I guess I should be happy. It does mean that the situation you see
isn't exactly the normal case. I understand why you want to do the
non-cached case, but the case I think it the worrisome one is the
regular buffered one, so that's what I'm testing (not even trying the
noaccess patches).
So from your report I went "uhhuh, that sounds like a bug". And it
appears that it largely isn't - you're seeing it because of pushing
the IO subsystem by another order of magnitude (and then I agree that
"under those kinds of IO loads, caching just won't help")
Linus
