On Thu, Dec 10, 2015 at 02:39:19PM +0300, Vladimir Davydov wrote:
> Swap cache pages are freed aggressively if swap is nearly full (>50%
> currently), because otherwise we are likely to stop scanning anonymous
> when we near the swap limit even if there is plenty of freeable swap
> cache pages. We should follow the same trend in case of memory cgroup,
> which has its own swap limit.
>
> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
One note:
> @@ -5839,6 +5839,29 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
> return nr_swap_pages;
> }
>
> +bool mem_cgroup_swap_full(struct page *page)
> +{
> + struct mem_cgroup *memcg;
> +
> + VM_BUG_ON_PAGE(!PageLocked(page), page);
> +
> + if (vm_swap_full())
> + return true;
> + if (!do_swap_account || !PageSwapCache(page))
> + return false;
The callers establish PageSwapCache() under the page lock, which makes
sense since they only inquire about the swap state when deciding what
to do with a swapcache page at hand. So this check seems unnecessary.
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