On 12/11/19 6:08 PM, Linus Torvalds wrote: > On Wed, Dec 11, 2019 at 3:41 PM Jens Axboe <axboe@xxxxxxxxx> wrote: >> >> Here's what I did to reproduce: > > Gaah. I have a fairly fast ssd (but it's "consumer fast" - Samsung 970 > Pro - I'm assuming yours is a different class), but I encrypt my disk, > so I only get about 15k iops and I see kcyrptd in my profiles, not > kswapd. > > I didn't even try to worry about RWF_UNCACHED or RWF_NOACCESS, since I > wanted to see the problem. But I think that with my setup, I can't > really see it just due to my IO being slow ;( > > I do see xas_create and kswapd0, but it's 0.42%. I'm assuming it's the > very first signs of this problem, but it's certainly not all that > noticeable. 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? I always set aside a decently sized empty partition on my laptop to be able to run these kinds of things without having to resort to a test box. Latency is where it's down the most, you'll likely do better with more threads to get the IOPS up. -- Jens Axboe
