Re: [PATCH -mmotm 7/8] memcg: move charges of anonymous swap

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 21 Dec 2009 14:38:16 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> This patch is another core part of this move-charge-at-task-migration feature.
> It enables moving charges of anonymous swaps.
> 
> To move the charge of swap, we need to exchange swap_cgroup's record.
> 
> In current implementation, swap_cgroup's record is protected by:
> 
>   - page lock: if the entry is on swap cache.
>   - swap_lock: if the entry is not on swap cache.
> 
> This works well in usual swap-in/out activity.
> 
> But this behavior make the feature of moving swap charge check many conditions
> to exchange swap_cgroup's record safely.
> 
> So I changed modification of swap_cgroup's recored(swap_cgroup_record())
> to use xchg, and define a new function to cmpxchg swap_cgroup's record.
> 
> This patch also enables moving charge of non pte_present but not uncharged swap
> caches, which can be exist on swap-out path, by getting the target pages via
> find_get_page() as do_mincore() does.
> 
>
> ...
>
> +		else if (is_swap_pte(ptent)) {

is_swap_pte() isn't implemented for CONFIG_MMU=n, so the build breaks.

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