mm: remove SWAP_AGAIN in ttu (33fc80e2) · Commits · 戴 / test

In 2002, [1] introduced SWAP_AGAIN. At that time, try_to_unmap_one used spin_trylock(&mm->page_table_lock) so it's really easy to contend and fail to hold a lock so SWAP_AGAIN to keep LRU status makes sense. However, now we changed it to mutex-based lock and be able to block without skip pte so there is few of small window to return SWAP_AGAIN so remove SWAP_AGAIN and just return SWAP_FAIL. [1] , minimal rmap Link: http://lkml.kernel.org/r/1489555493-14659-7-git-send-email-minchan@kernel.org Signed-off-by:

Minchan Kim <minchan@kernel.org> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/rmap.c

+3 −8

Original line number	Diff line number	Diff line
		@@ -1504,13 +1504,10 @@ static int page_mapcount_is_zero(struct page *page)
		* Return values are:
		*
		* SWAP_SUCCESS - we succeeded in removing all mappings
		* SWAP_AGAIN - we missed a mapping, try again later
		* SWAP_FAIL - the page is unswappable
		*/
		int try_to_unmap(struct page *page, enum ttu_flags flags)
		{
		int ret;

		struct rmap_walk_control rwc = {
		.rmap_one = try_to_unmap_one,
		.arg = (void *)flags,
		@@ -1530,13 +1527,11 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
		rwc.invalid_vma = invalid_migration_vma;

		if (flags & TTU_RMAP_LOCKED)
		ret = rmap_walk_locked(page, &rwc);
		rmap_walk_locked(page, &rwc);
		else
		ret = rmap_walk(page, &rwc);
		rmap_walk(page, &rwc);

		if (!page_mapcount(page))
		ret = SWAP_SUCCESS;
		return ret;
		return !page_mapcount(page) ? SWAP_SUCCESS : SWAP_FAIL;
		}

		static int page_not_mapped(struct page *page)

mm/vmscan.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -1150,8 +1150,6 @@ static unsigned long shrink_page_list(struct list_head *page_list,
		case SWAP_FAIL:
		nr_unmap_fail++;
		goto activate_locked;
		case SWAP_AGAIN:
		goto keep_locked;
		case SWAP_SUCCESS:
		; /* try to free the page below */
		}

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