Re: [PATCH v7] mm: shrink skip folio mapped by an exiting process

[Andrew Morton]

On Tue,  9 Jul 2024 20:31:15 +0800 Zhiguo Jiang <justinjiang@xxxxxxxx> wrote:

> The releasing process of the non-shared anonymous folio mapped solely by
> an exiting process may go through two flows: 1) the anonymous folio is
> firstly is swaped-out into swapspace and transformed into a swp_entry
> in shrink_folio_list; 2) then the swp_entry is released in the process
> exiting flow. This will result in the high cpu load of releasing a
> non-shared anonymous folio mapped solely by an exiting process.
> 
> When the low system memory and the exiting process exist at the same
> time, it will be likely to happen, because the non-shared anonymous
> folio mapped solely by an exiting process may be reclaimed by
> shrink_folio_list.
> 
> This patch is that shrink skips the non-shared anonymous folio solely
> mapped by an exting process and this folio is only released directly in
> the process exiting flow, which will save swap-out time and alleviate
> the load of the process exiting. 

It would be helpful to provide some before-and-after runtime
measurements, please.  It's a performance optimization so please let's
see what effect it has.