[Devel] [PATCH -RSS 2/2] Fix limit check after reclaim

[Balbir Singh]

This patch modifies the reclaim behaviour such that before calling the
container out of memory routine, it checks if as a result of the reclaim
(even though pages might not be fully reclaimed), the resident set size
of the container decreased before declaring the container as out of memory

Signed-off-by: Balbir Singh <balbir at linux.vnet.ibm.com>
---

 include/linux/res_counter.h |   23 +++++++++++++++++++++++
 mm/rss_container.c          |   11 +++++++++++
 2 files changed, 34 insertions(+)

diff -puN mm/rss_container.c~rss-fix-limit-check-after-reclaim mm/rss_container.c
--- linux-2.6.22-rc2-mm1/mm/rss_container.c~rss-fix-limit-check-after-reclaim	2007-06-04 20:13:40.000000000 +0530
+++ linux-2.6.22-rc2-mm1-balbir/mm/rss_container.c	2007-06-04 20:13:40.000000000 +0530
@@ -114,6 +114,17 @@ int container_rss_prepare(struct page *p
 			continue;
 		}
 
+		/*
+ 		 * try_to_free_pages() might not give us a full picture
+ 		 * of reclaim. Some pages are reclaimed and might be moved
+ 		 * to swap cache or just unmapped from the container.
+ 		 * Check the limit again to see if the reclaim reduced the
+ 		 * current usage of the container before calling the
+ 		 * container OOM routine
+ 		 */
+		if (res_counter_check_under_limit(&rss->res))
+			continue;
+
 		container_out_of_memory(rss);
 		if (test_thread_flag(TIF_MEMDIE))
 			goto out_charge;
diff -puN include/linux/res_counter.h~rss-fix-limit-check-after-reclaim include/linux/res_counter.h
--- linux-2.6.22-rc2-mm1/include/linux/res_counter.h~rss-fix-limit-check-after-reclaim	2007-06-04 20:13:40.000000000 +0530
+++ linux-2.6.22-rc2-mm1-balbir/include/linux/res_counter.h	2007-06-04 20:15:46.000000000 +0530
@@ -99,4 +99,27 @@ int res_counter_charge(struct res_counte
 void res_counter_uncharge_locked(struct res_counter *cnt, unsigned long val);
 void res_counter_uncharge(struct res_counter *cnt, unsigned long val);
 
+static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
+{
+	if (cnt->usage < cnt->limit)
+		return true;
+
+	return false;
+}
+
+/*
+ * Helper function to detect if the container is within it's limit or
+ * not. It's currently called from container_rss_prepare()
+ */
+static inline bool res_counter_check_under_limit(struct res_counter *cnt)
+{
+	bool ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cnt->lock, flags);
+	ret = res_counter_limit_check_locked(cnt);
+	spin_unlock_irqrestore(&cnt->lock, flags);
+	return ret;
+}
+
 #endif
diff -puN mm/vmscan.c~rss-fix-limit-check-after-reclaim mm/vmscan.c
_

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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