On Sat, Sep 22, 2012 at 04:03:11PM +0530, raghu.prabhu13@xxxxxxxxx wrote:
> From: Raghavendra D Prabhu <rprabhu@xxxxxxxxxxx>
>
> If page lookup from radix_tree_lookup is successful and its index page_idx ==
> nr_to_read - lookahead_size, then SetPageReadahead never gets called, so this
> fixes that.
NAK. Sorry. It's actually an intentional behavior, so that for the
common cases of many cached files that are accessed frequently, no
PG_readahead will be set at all to pointlessly trap into the readahead
routines once and again.
Perhaps we need a patch for commenting that case. :)
Thanks,
Fengguang
> Signed-off-by: Raghavendra D Prabhu <rprabhu@xxxxxxxxxxx>
> ---
> mm/readahead.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/readahead.c b/mm/readahead.c
> index 461fcc0..fec726c 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -189,8 +189,10 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
> break;
> page->index = page_offset;
> list_add(&page->lru, &page_pool);
> - if (page_idx == nr_to_read - lookahead_size)
> + if (page_idx >= nr_to_read - lookahead_size) {
> SetPageReadahead(page);
> + lookahead_size = 0;
> + }
> ret++;
> }
>
> --
> 1.7.12.1
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