Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter

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KAMEZAWA Hiroyuki wrote:
On Fri, 02 Mar 2012 09:51:27 +0400
Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>  wrote:

KAMEZAWA Hiroyuki wrote:
On Wed, 29 Feb 2012 13:15:47 +0400
Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>   wrote:

This patch adds file/anon filter bits into isolate_mode_t,
this allows to simplify checks in __isolate_lru_page().

Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>

Hmm.. I like idea but..

---
   include/linux/mmzone.h |    4 ++++
   include/linux/swap.h   |    2 +-
   mm/compaction.c        |    5 +++--
   mm/vmscan.c            |   27 +++++++++++++--------------
   4 files changed, 21 insertions(+), 17 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index eff4918..2fed935 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -193,6 +193,10 @@ struct lruvec {
   #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
   /* Isolate for asynchronous migration */
   #define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
+/* Isolate swap-backed pages */
+#define	ISOLATE_ANON		((__force isolate_mode_t)0x20)
+/* Isolate file-backed pages */
+#define	ISOLATE_FILE		((__force isolate_mode_t)0x40)

   /* LRU Isolation modes. */
   typedef unsigned __bitwise__ isolate_mode_t;
diff --git a/include/linux/swap.h b/include/linux/swap.h
index ba2c8d7..dc6e6a3 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -254,7 +254,7 @@ static inline void lru_cache_add_file(struct page *page)
   /* linux/mm/vmscan.c */
   extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
   					gfp_t gfp_mask, nodemask_t *mask);
-extern int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file);
+extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
   extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
   						  gfp_t gfp_mask, bool noswap);
   extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
diff --git a/mm/compaction.c b/mm/compaction.c
index 74a8c82..cc054f7 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -261,7 +261,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
   	unsigned long last_pageblock_nr = 0, pageblock_nr;
   	unsigned long nr_scanned = 0, nr_isolated = 0;
   	struct list_head *migratelist =&cc->migratepages;
-	isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
+	isolate_mode_t mode = ISOLATE_ACTIVE | ISOLATE_INACTIVE |
+			      ISOLATE_FILE | ISOLATE_ANON;

   	/* Do not scan outside zone boundaries */
   	low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
@@ -375,7 +376,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
   			mode |= ISOLATE_ASYNC_MIGRATE;

   		/* Try isolate the page */
-		if (__isolate_lru_page(page, mode, 0) != 0)
+		if (__isolate_lru_page(page, mode) != 0)
   			continue;

   		VM_BUG_ON(PageTransCompound(page));
diff --git a/mm/vmscan.c b/mm/vmscan.c
index af6cfe7..1b70338 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1029,27 +1029,18 @@ keep_lumpy:
    *
    * returns 0 on success, -ve errno on failure.
    */
-int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
+int __isolate_lru_page(struct page *page, isolate_mode_t mode)
   {
-	bool all_lru_mode;
   	int ret = -EINVAL;

   	/* Only take pages on the LRU. */
   	if (!PageLRU(page))
   		return ret;

-	all_lru_mode = (mode&   (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
-		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);
-
-	/*
-	 * When checking the active state, we need to be sure we are
-	 * dealing with comparible boolean values.  Take the logical not
-	 * of each.
-	 */
-	if (!all_lru_mode&&   !PageActive(page) != !(mode&   ISOLATE_ACTIVE))
+	if (!(mode&   (PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE)))
   		return ret;

Isn't this complicated ?

But it doesn't blows my mind as old code does =)

Maybe someone can propose more clear variant?


switch (mode&  (ISOLATE_ACTIVE | ISOLATE_INACTIVE)) {
	case ISOLATE_ACTIVE :
		if (!PageActive(page))
			return ret;
	case ISOLATE_INACTIVE :
		if (PageActive(page))
			return ret;
	default:
		break;
	}
}

?

Thanks. It is more optimal and looks more simple. but you lost one "break"


Thanks,
-Kame



-	if (!all_lru_mode&&   !!page_is_file_cache(page) != file)
+	if (!(mode&   (page_is_file_cache(page) ? ISOLATE_FILE : ISOLATE_ANON)))
   		return ret;

   	/*

ditto.

Where is simple  ?

Thanks,
-Kame


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