Re: [PATCH 3/3] Provide control over unmapped pages

KAMEZAWA Hiroyuki
2010-12-01T01:38:33Z

On Tue, 30 Nov 2010 15:46:31 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> Provide control using zone_reclaim() and a boot parameter. The
> code reuses functionality from zone_reclaim() to isolate unmapped
> pages and reclaim them as a priority, ahead of other mapped pages.
>
> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
> include/linux/swap.h | 5 ++-
> mm/page_alloc.c | 7 +++--
> mm/vmscan.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 79 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index eba53e7..78b0830 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -252,11 +252,12 @@ extern int vm_swappiness;
> extern int remove_mapping(struct address_space *mapping, struct page *page);
> extern long vm_total_pages;
>
> -#ifdef CONFIG_NUMA
> -extern int zone_reclaim_mode;
> extern int sysctl_min_unmapped_ratio;
> extern int sysctl_min_slab_ratio;
> extern int zone_reclaim(struct zone *, gfp_t, unsigned int);
> +extern bool should_balance_unmapped_pages(struct zone *zone);
> +#ifdef CONFIG_NUMA
> +extern int zone_reclaim_mode;
> #else
> #define zone_reclaim_mode 0
> static inline int zone_reclaim(struct zone *z, gfp_t mask, unsigned int order)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 62b7280..4228da3 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1662,6 +1662,9 @@ zonelist_scan:
> unsigned long mark;
> int ret;
>
> + if (should_balance_unmapped_pages(zone))
> + wakeup_kswapd(zone, order);
> +

Hm, I'm not sure the final vision of this feature. Does this reclaiming feature
can't be called directly via balloon driver just before alloc_page() ?

Do you need to keep page caches small even when there are free memory on host ?

Thanks,
-Kame