Re: Low TCP throughput due to vmpressure with swap enabled

On Tue, Nov 22, 2022 at 12:05 PM Ivan Babrou [off-list ref] wrote:

On Tue, Nov 22, 2022 at 10:59 AM Yu Zhao [off-list ref] wrote:

quoted

On Mon, Nov 21, 2022 at 5:53 PM Ivan Babrou [off-list ref] wrote:

quoted

Hello,

We have observed a negative TCP throughput behavior from the following commit:

* 8e8ae645249b mm: memcontrol: hook up vmpressure to socket pressure

It landed back in 2016 in v4.5, so it's not exactly a new issue.

The crux of the issue is that in some cases with swap present the
workload can be unfairly throttled in terms of TCP throughput.

I am able to reproduce this issue in a VM locally on v6.1-rc6 with 8
GiB of RAM with zram enabled.

Hi Ivan,

If it's not too much trouble, could you try again with the following?
  CONFIG_LRU_GEN=y
  CONFIG_LRU_GEN_ENABLED=y

I haven't tried it myself. But I'll fix whatever doesn't work for you,
since your team is on the top of my customer list :)

We don't have it in production, since there we have 5.15 LTS (our
kernel team is testing v6.1).

I do have it enabled in my VM running v6.1-rc6 where I was able to
replicate this, so it doesn't seem to help.

Thanks. I'll look into this and get back to you.