Re: [RFC PATCH v0.1 0/9] UMCG early preview/RFC patchset

On Fri, May 21, 2021 at 11:44 AM Andrei Vagin [off-list ref] wrote:

On Thu, May 20, 2021 at 11:36 AM Peter Oskolkov [off-list ref] wrote:

quoted

As indicated earlier in the FUTEX_SWAP patchset:

https://lore.kernel.org/lkml/20200722234538.166697-1-posk@posk.io/ (local)

Hi Peter,

Do you have benchmark results? How fast is it compared with futex_swap and the google switchto?

Hi Andrei,

I did not run benchmarks on the same machine/kernel, but umcg_swap
between "core" tasks (your use case for gVisor) should be somewhat
faster than futex_swap, as there is no reading from the userspace and
no futex hash lookup/dequeue ops; umcg_swap should be slower than
switchto_switch because umcg_swap does go through ttwu+schedule, which
switchto_switch bypasses.

I expect that if UMCG is merged in a form similar to what I posted, we
will explore how to make UMCG context switches faster in later
patches.

Thanks,
Peter

Thanks,
Andrei