Re: [PATCH] block/psi: make PSI annotations of submit_bio only work for file pages

[Johannes Weiner]

On Wed, Mar 16, 2022 at 06:39:28AM +0000, cgel.zte@xxxxxxxxx wrote:
> From: Yang Yang <yang.yang29@xxxxxxxxxx>
> 
> psi tracks the time spent on submitting the IO of refaulting file pages
> and anonymous pages[1]. But after we tracks refaulting anonymous pages
> in swap_readpage[2][3], there is no need to track refaulting anonymous
> pages in submit_bio.
> 
> So this patch can reduce redundant calling of psi_memstall_enter. And
> make it easier to track refaulting file pages and anonymous pages
> separately.

I don't think this is an improvement.

psi_memstall_enter() will check current->in_memstall once, detect the
nested call, and bail. Your patch checks PageSwapBacked for every page
being added. It's more branches for less robust code.