On Wed, Mar 09, 2011 at 04:48:01PM +0900, KAMEZAWA Hiroyuki wrote:
> On Wed, 9 Mar 2011 15:07:50 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>
> > > } else {
> > > /* shmem */
> > > if (PageSwapCache(page)) {
> > > ..
> > > } else {
> > > ..
> > > }
> > > }
> > >
> > > Otherwise, the page cache will be charged twice.
> > >
> >
> > Ahh, thanks. I'll send v3.
> >
>
> Okay, this is a fixed one.
> ==
>
> fs/fuse/dev.c::fuse_try_move_page() does
>
> (1) remove a page by ->steal()
> (2) re-add the page to page cache
> (3) link the page to LRU if it was not on LRU at (1)
>
> This implies the page is _on_ LRU when it's added to radix-tree.
> So, the page is added to memory cgroup while it's on LRU.
> because LRU is lazy and no one flushs it.
>
> This is the same behavior as SwapCache and needs special care as
> - remove page from LRU before overwrite pc->mem_cgroup.
> - add page to LRU after overwrite pc->mem_cgroup.
>
> And we need to taking care of pagevec.
>
> If PageLRU(page) is set before we add PCG_USED bit, the page
> will not be added to memcg's LRU (in short period).
> So, regardlress of PageLRU(page) value before commit_charge(),
> we need to check PageLRU(page) after commit_charge().
>
> Changelog v2=>v3:
> - fixed double accounting.
>
> Changelog v1=>v2:
> - clean up.
> - cover !PageLRU() by pagevec case.
>
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Thanks for the fix. I have a few comments below. Only nitpicks
though, the patch looks correct to me.
Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> @@ -2431,9 +2430,28 @@ static void
> __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
> enum charge_type ctype);
>
> +static void
> +__mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *mem,
> + enum charge_type ctype)
> +{
> + struct page_cgroup *pc = lookup_page_cgroup(page);
> + /*
> + * In some case, SwapCache, FUSE(splice_buf->radixtree), the page
> + * is already on LRU. It means the page may on some other page_cgroup's
> + * LRU. Take care of it.
> + */
> + if (unlikely(PageLRU(page)))
> + mem_cgroup_lru_del_before_commit(page);
Do we need the extra check? mem_cgroup_lru_del_before_commit() will
do the right thing if the page is not on the list.
> + __mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
> + if (unlikely(PageLRU(page)))
> + mem_cgroup_lru_add_after_commit(page);
Same here, mem_cgroup_lru_add_after_commit() has its own check for
PG_lru.
> @@ -2468,14 +2486,16 @@ int mem_cgroup_cache_charge(struct page
> if (unlikely(!mm))
> mm = &init_mm;
>
> - if (page_is_file_cache(page))
> - return mem_cgroup_charge_common(page, mm, gfp_mask,
> - MEM_CGROUP_CHARGE_TYPE_CACHE);
> -
> + if (page_is_file_cache(page)) {
> + ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, &mem, true);
> + if (ret || !mem)
> + return ret;
> + __mem_cgroup_commit_charge_lrucare(page, mem,
> + MEM_CGROUP_CHARGE_TYPE_CACHE);
I think the comment about why we need to take care of the LRU status
would make more sense here (rather than in the _lrucare function),
because it is here where you make handling the lru a consequence of
the page being a file page.
How about this?
/*
* FUSE reuses pages without going through the final
* put that would remove them from the LRU list, make
* sure that they get relinked properly.
*/
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>