2024-02-26 18:25:56

by Matthew Wilcox

Subject: Re: [PATCH 05/13] readahead: set file_ra_state->ra_pages to be at least mapping_min_order

On Mon, Feb 26, 2024 at 10:49:28AM +0100, Pankaj Raghav (Samsung) wrote:
> From: Luis Chamberlain <[email protected]>
>
> Set the file_ra_state->ra_pages in file_ra_state_init() to be at least
> mapping_min_order of pages if the bdi->ra_pages is less than that.

Don't we rather want to round up to a multiple of mapping_min_nrpages?

> file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
> {
> + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping);
> +
> ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
> + if (ra->ra_pages < min_nrpages)
> + ra->ra_pages = min_nrpages;
> ra->prev_pos = -1;

2024-02-28 09:50:21

by Pankaj Raghav (Samsung)

Subject: Re: [PATCH 05/13] readahead: set file_ra_state->ra_pages to be at least mapping_min_order

On Mon, Feb 26, 2024 at 02:49:04PM +0000, Matthew Wilcox wrote:
> On Mon, Feb 26, 2024 at 10:49:28AM +0100, Pankaj Raghav (Samsung) wrote:
> > From: Luis Chamberlain <[email protected]>
> >
> > Set the file_ra_state->ra_pages in file_ra_state_init() to be at least
> > mapping_min_order of pages if the bdi->ra_pages is less than that.
>
> Don't we rather want to round up to a multiple of mapping_min_nrpages?

Hmm. That will definitely be more explicit. We might be doing
multiple of min_nrpages now anyway, going beyond the ra_pages(if it
is not a multiple of min_nrpages).

I will do this instead:

diff --git a/mm/readahead.c b/mm/readahead.c
index 73aef3f080ba..4e3a6f763f5c 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -138,11 +138,8 @@
void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
{
- unsigned int min_nrpages = mapping_min_folio_nrpages(mapping);
-
- ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
- if (ra->ra_pages < min_nrpages)
- ra->ra_pages = min_nrpages;
+ ra->ra_pages = round_up(inode_to_bdi(mapping->host)->ra_pages,
+ mapping_min_folio_nrpages(mapping));
ra->prev_pos = -1;
}

>
> > file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
> > {
> > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping);
> > +
> > ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
> > + if (ra->ra_pages < min_nrpages)
> > + ra->ra_pages = min_nrpages;
> > ra->prev_pos = -1;