Hey Ryan, On Wed, Apr 30, 2025 at 03:59:14PM +0100, Ryan Roberts wrote: > FOLIO 0x0001a000 0x0001b000 4096 26 27 1 0 > FOLIO 0x0001b000 0x0001c000 4096 27 28 1 0 > FOLIO 0x0001c000 0x0001d000 4096 28 29 1 0 > FOLIO 0x0001d000 0x0001e000 4096 29 30 1 0 > FOLIO 0x0001e000 0x0001f000 4096 30 31 1 0 > FOLIO 0x0001f000 0x00020000 4096 31 32 1 0 > FOLIO 0x00020000 0x00024000 16384 32 36 4 2 > FOLIO 0x00024000 0x00028000 16384 36 40 4 2 > FOLIO 0x00028000 0x0002c000 16384 40 44 4 2 > FOLIO 0x0002c000 0x00030000 16384 44 48 4 2 > ... > > Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> > --- > mm/readahead.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 6a4e96b69702..8bb316f5a842 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -479,9 +479,6 @@ void page_cache_ra_order(struct readahead_control *ractl, > So we always had a fallback to do_page_cache_ra() if the size of the readahead is less than 4 pages (16k). I think this was there because we were adding `2` to the new_order: unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping)); /* * Fallback when size < min_nrpages as each folio should be * at least min_nrpages anyway. */ if (!mapping_large_folio_support(mapping) || ra->size < min_ra_size) goto fallback; > limit = min(limit, index + ra->size - 1); > > - if (new_order < mapping_max_folio_order(mapping)) > - new_order += 2; Now that you have moved this, we could make the lhs of the max to be 2 (8k) instead of 4(16k). - unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping)); + unsigned int min_ra_size = max(2, mapping_min_folio_nrpages(mapping)); I think if we do that, we might ramp up to 8k sooner rather than jumping from 4k to 16k directly? > - > new_order = min(mapping_max_folio_order(mapping), new_order); > new_order = min_t(unsigned int, new_order, ilog2(ra->size)); > new_order = max(new_order, min_order); > @@ -683,6 +680,7 @@ void page_cache_async_ra(struct readahead_control *ractl, > ra->size = get_next_ra_size(ra, max_pages); > ra->async_size = ra->size; > readit: > + order += 2; > ractl->_index = ra->start; > page_cache_ra_order(ractl, ra, order); > } > -- > 2.43.0 > -- Pankaj
