On Thu, 25 Jun 2020 01:43:32 +0800 Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> wrote:
> Since commit bbddabe2e436aa7869b3ac5248df5c14ddde0cbf ("mm: filemap:
> only do access activations on reads"), mark_page_accessed() is called
> for reads only. But the idle flag is cleared by mark_page_accessed() so
> the idle flag won't get cleared if the page is write accessed only.
>
> Basically idle page tracking is used to estimate workingset size of
> workload, noticeable size of workingset might be missed if the idle flag
> is not maintained correctly.
>
> It seems good enough to just clear idle flag for write operations.
>
> ...
>
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -41,6 +41,7 @@
> #include <linux/delayacct.h>
> #include <linux/psi.h>
> #include <linux/ramfs.h>
> +#include <linux/page_idle.h>
> #include "internal.h"
>
> #define CREATE_TRACE_POINTS
> @@ -1630,6 +1631,11 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
>
> if (fgp_flags & FGP_ACCESSED)
> mark_page_accessed(page);
> + else if (fgp_flags & FGP_WRITE) {
> + /* Clear idle flag for buffer write */
> + if (page_is_idle(page))
> + clear_page_idle(page);
> + }
>
> no_page:
> if (!page && (fgp_flags & FGP_CREAT)) {
The kerneldoc comment for pagecache_get_page() could do with some
updating - it fails to mention FGP_WRITE, FGP_NOFS and FGP_NOWAIT.
This change seems correct but also will have runtime effects. What are
they?
