Re: [PATCH 13/16] mm: fix minor scan count bugs

[Nick Piggin]

Wu Fengguang wrote:
> - in isolate_lru_pages(): reports one more scan. Fix it.
> - in shrink_cache(): 0 pages taken does not mean 0 pages scanned. Fix it.

This looks good, although in the first hunk it might be nicer
to turn it into the more familiar for-loop.

  for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {

> Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
> ---
>
>  mm/vmscan.c |   10 ++++++----
>  1 files changed, 6 insertions(+), 4 deletions(-)
>
> --- linux.orig/mm/vmscan.c
> +++ linux/mm/vmscan.c
> @@ -864,7 +864,8 @@ static int isolate_lru_pages(int nr_to_s
>  	struct page *page;
>  	int scan = 0;
>  
> -	while (scan++ < nr_to_scan && !list_empty(src)) {
> +	while (scan < nr_to_scan && !list_empty(src)) {
> +		scan++;
>  		page = lru_to_page(src);
>  		prefetchw_prev_lru_page(page, src, flags);
>  
> @@ -911,14 +912,15 @@ static void shrink_cache(struct zone *zo
>  	update_zone_age(zone, nr_scan);
>  	spin_unlock_irq(&zone->lru_lock);
>  
> -	if (nr_taken == 0)
> -		return;
> -
>  	sc->nr_scanned += nr_scan;
>  	if (current_is_kswapd())
>  		mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
>  	else
>  		mod_page_state_zone(zone, pgscan_direct, nr_scan);
> +
> +	if (nr_taken == 0)
> +		return;
> +
>  	nr_freed = shrink_list(&page_list, sc);
>  	if (current_is_kswapd())
>  		mod_page_state(kswapd_steal, nr_freed);

--
SUSE Labs, Novell Inc.

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