Re: [patch 21/21] cull non-reclaimable anon pages from the LRU at fault time

Lee Schermerhorn
2008-02-28T20:19:33Z

On Thu, 2008-02-28 at 14:29 -0500, Rik van Riel wrote:

corrections to description in case we decide to keep this patch.

> V2 -> V3:
> + rebase to 23-mm1 atop RvR's split lru series.
>
> V1 -> V2:
> + no changes
>
> Optional part of "noreclaim infrastructure"
>
> In the fault paths that install new anonymous pages, check whether
> the page is reclaimable or not using lru_cache_add_active_or_noreclaim().
> If the page is reclaimable, just add it to the active lru list [via
> the pagevec cache], else add it to the noreclaim list.
>
> This "proactive" culling in the fault path mimics the handling of
> mlocked pages in Nick Piggin's series to keep mlocked pages off
> the lru lists.
>
> Notes:
>
> 1) This patch is optional--e.g., if one is concerned about the
> additional test in the fault path. We can defer the moving of
> nonreclaimable pages until when vmscan [shrink_*_list()]
> encounters them. Vmscan will only need to handle such pages
> once.
>
> 2) I moved the call to page_add_new_anon_rmap() to before the test
> for page_reclaimable() and thus before the calls to
> lru_cache_add_{active|noreclaim}(), so that page_reclaimable()
> could recognize the page as anon,
<snip the bit about the vma arg. replaced with new note 3 below>
> TBD: I think this reordering is OK, but the previous order may
> have existed to close some obscure race?
>
<delete prev note 3, as it referred to patches that are no longer in the
series [altho' I continue to maintain them separately, "just in case"].
replace with this note about vma arg to page_reclaimable()>

3) The 'vma' argument to page_reclaimable() is require to notice that
we're faulting a page into an mlock()ed vma w/o having to scan the
page's rmap in the fault path. Culling mlock()ed anon pages is
currently the only reason for this patch.
>
> Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
> Signed-off-by: Rik van Riel <riel@redhat.com>
>
> Index: linux-2.6.25-rc2-mm1/mm/memory.c
> ===================================================================
> --- linux-2.6.25-rc2-mm1.orig/mm/memory.c 2008-02-28 00:27:06.000000000 -0500
> +++ linux-2.6.25-rc2-mm1/mm/memory.c 2008-02-28 12:49:23.000000000 -0500
> @@ -1678,7 +1678,7 @@ gotten:
> set_pte_at(mm, address, page_table, entry);
> update_mmu_cache(vma, address, entry);
> SetPageSwapBacked(new_page);
> - lru_cache_add_active_anon(new_page);
> + lru_cache_add_active_or_noreclaim(new_page, vma);
> page_add_new_anon_rmap(new_page, vma, address);
>
> /* Free the old page.. */
> @@ -2150,7 +2150,7 @@ static int do_anonymous_page(struct mm_s
> goto release;
> inc_mm_counter(mm, anon_rss);
> SetPageSwapBacked(page);
> - lru_cache_add_active_anon(page);
> + lru_cache_add_active_or_noreclaim(page, vma);
> page_add_new_anon_rmap(page, vma, address);
> set_pte_at(mm, address, page_table, entry);
>
> @@ -2292,10 +2292,10 @@ static int __do_fault(struct mm_struct *
> entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> set_pte_at(mm, address, page_table, entry);
> if (anon) {
> - inc_mm_counter(mm, anon_rss);
> + inc_mm_counter(mm, anon_rss);
> SetPageSwapBacked(page);
> - lru_cache_add_active_anon(page);
> - page_add_new_anon_rmap(page, vma, address);
> + lru_cache_add_active_or_noreclaim(page, vma);
> + page_add_new_anon_rmap(page, vma, address);
> } else {
> inc_mm_counter(mm, file_rss);
> page_add_file_rmap(page);
> Index: linux-2.6.25-rc2-mm1/mm/swap_state.c
> ===================================================================
> --- linux-2.6.25-rc2-mm1.orig/mm/swap_state.c 2008-02-28 00:29:51.000000000 -0500
> +++ linux-2.6.25-rc2-mm1/mm/swap_state.c 2008-02-28 12:49:23.000000000 -0500
> @@ -300,7 +300,10 @@ struct page *read_swap_cache_async(swp_e
> /*
> * Initiate read into locked page and return.
> */
> - lru_cache_add_anon(new_page);
> + if (!page_reclaimable(new_page, vma))
> + lru_cache_add_noreclaim(new_page);
> + else
> + lru_cache_add_anon(new_page);
> swap_readpage(NULL, new_page);
> return new_page;
> }
>