[PATCH 3/3][RFC] Containers: Pagecache controller reclaim

[Vaidyanathan Srinivasan]

The reclaim code is similar to RSS memory controller.  Scan control is
slightly different since we are targeting different type of pages.

Additionally no mapped pages are touched when scanning for pagecache pages.

RSS memory controller and pagecache controller share common code in reclaim
and hence pagecache controller patches are dependent on RSS memory controller
patch even though the features are independently configurable at compile time.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx>
---
 include/linux/memcontrol.h |    6 +++
 mm/memcontrol.c            |    4 +-
 mm/pagecache_acct.c        |   11 ++++++
 mm/vmscan.c                |   71 +++++++++++++++++++++++++++++++++++++--------
 4 files changed, 77 insertions(+), 15 deletions(-)

--- linux-2.6.20.orig/include/linux/memcontrol.h
+++ linux-2.6.20/include/linux/memcontrol.h
@@ -36,6 +36,12 @@ enum {
 	MEMCONTROL_DONT_CHECK_LIMIT = false,
 };

+/* Type of memory to reclaim in shrink_container_memory() */
+enum {
+	RECLAIM_MAPPED_MEMORY = 1,
+	RECLAIM_PAGECACHE_MEMORY,
+};
+
 #ifdef CONFIG_CONTAINER_MEMCONTROL
 #include <linux/wait.h>

--- linux-2.6.20.orig/mm/memcontrol.c
+++ linux-2.6.20/mm/memcontrol.c
@@ -165,8 +165,8 @@ static int memcontrol_check_and_reclaim(
 				nr_pages = (pushback * limit) / 100;
 			mem->reclaim_in_progress = true;
 			spin_unlock(&mem->lock);
-			nr_reclaimed +=
-				memcontrol_shrink_mapped_memory(nr_pages, cont);
+			nr_reclaimed += shrink_container_memory(
+					RECLAIM_MAPPED_MEMORY, nr_pages, cont);
 			spin_lock(&mem->lock);
 			mem->reclaim_in_progress = false;
 			wake_up_all(&mem->wq);
--- linux-2.6.20.orig/mm/pagecache_acct.c
+++ linux-2.6.20/mm/pagecache_acct.c
@@ -29,6 +29,7 @@
 #include <linux/uaccess.h>
 #include <asm/div64.h>
 #include <linux/pagecache_acct.h>
+#include <linux/memcontrol.h>

 /*
  * Convert unit from pages to kilobytes
@@ -337,12 +338,20 @@ int pagecache_acct_cont_overlimit(struct
 		return 0;
 }

-extern unsigned long shrink_all_pagecache_memory(unsigned long nr_pages);
+extern unsigned long shrink_container_memory(unsigned int memory_type,
+				unsigned long nr_pages, void *container);

 int pagecache_acct_shrink_used(unsigned long nr_pages)
 {
 	unsigned long ret = 0;
 	atomic_inc(&reclaim_count);
+
+	/* Don't call reclaim for each page above limit */
+	if (nr_pages > NR_PAGES_RECLAIM_THRESHOLD) {
+		ret += shrink_container_memory(
+				RECLAIM_PAGECACHE_MEMORY, nr_pages, NULL);
+	}
+
 	return 0;
 }

--- linux-2.6.20.orig/mm/vmscan.c
+++ linux-2.6.20/mm/vmscan.c
@@ -43,6 +43,7 @@

 #include <linux/swapops.h>
 #include <linux/memcontrol.h>
+#include <linux/pagecache_acct.h>

 #include "internal.h"

@@ -70,6 +71,8 @@ struct scan_control {

 	struct container *container;	/* Used by containers for reclaiming */
 					/* pages when the limit is exceeded  */
+	int reclaim_pagecache_only;     /* Set when called from
+					   pagecache controller */
 };

 /*
@@ -474,6 +477,15 @@ static unsigned long shrink_page_list(st
 			goto keep;

 		VM_BUG_ON(PageActive(page));
+		/* Take it easy if we are doing only pagecache pages */
+		if (sc->reclaim_pagecache_only) {
+			/* Check if this is a pagecache page they are not mapped */
+			if (page_mapped(page))
+				goto keep_locked;
+			/* Check if this container has exceeded pagecache limit */
+			if (!pagecache_acct_page_overlimit(page))
+				goto keep_locked;
+		}

 		sc->nr_scanned++;

@@ -522,7 +534,8 @@ static unsigned long shrink_page_list(st
 		}

 		if (PageDirty(page)) {
-			if (referenced)
+			/* Reclaim even referenced pagecache pages if over limit */
+			if (!pagecache_acct_page_overlimit(page) && referenced)
 				goto keep_locked;
 			if (!may_enter_fs)
 				goto keep_locked;
@@ -869,6 +882,13 @@ force_reclaim_mapped:
 		cond_resched();
 		page = lru_to_page(&l_hold);
 		list_del(&page->lru);
+		/* While reclaiming pagecache make it easy */
+		if (sc->reclaim_pagecache_only) {
+			if (page_mapped(page) || !pagecache_acct_page_overlimit(page)) {
+				list_add(&page->lru, &l_active);
+				continue;
+			}
+		}
 		if (page_mapped(page)) {
 			if (!reclaim_mapped ||
 			    (total_swap_pages == 0 && PageAnon(page)) ||
@@ -1064,6 +1084,7 @@ unsigned long try_to_free_pages(struct z
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
 		.may_swap = 1,
 		.swappiness = vm_swappiness,
+		.reclaim_pagecache_only = 0,
 	};

 	count_vm_event(ALLOCSTALL);
@@ -1168,6 +1189,7 @@ static unsigned long balance_pgdat(pg_da
 		.may_swap = 1,
 		.swap_cluster_max = SWAP_CLUSTER_MAX,
 		.swappiness = vm_swappiness,
+		.reclaim_pagecache_only = 0,
 	};
 	/*
 	 * temp_priority is used to remember the scanning priority at which
@@ -1398,7 +1420,9 @@ void wakeup_kswapd(struct zone *zone, in
 	wake_up_interruptible(&pgdat->kswapd_wait);
 }

-#if defined(CONFIG_PM) || defined(CONFIG_CONTAINER_MEMCONTROL)
+#if defined(CONFIG_PM) || defined(CONFIG_CONTAINER_MEMCONTROL) \
+	|| defined(CONFIG_CONTAINER_PAGECACHE_ACCT)
+
 /*
  * Helper function for shrink_all_memory().  Tries to reclaim 'nr_pages' pages
  * from LRU lists system-wide, for given pass and priority, and returns the
@@ -1470,11 +1494,13 @@ unsigned long shrink_all_memory(unsigned
 	int pass;
 	struct reclaim_state reclaim_state;
 	struct scan_control sc = {
-		.gfp_mask = GFP_KERNEL,
+		.gfp_mask = GFdefined(CONFIG_CONTAINER_PAGECACHE_ACCT)
+P_KERNEL,
 		.may_swap = 0,
 		.swap_cluster_max = nr_pages,
 		.may_writepage = 1,
 		.swappiness = vm_swappiness,
+		.reclaim_pagecache_only = 0,
 	};

 	current->reclaim_state = &reclaim_state;
@@ -1551,33 +1577,53 @@ out:
 }
 #endif

-#ifdef CONFIG_CONTAINER_MEMCONTROL
+#if defined(CONFIG_CONTAINER_MEMCTLR) || \
+	defined(CONFIG_CONTAINER_PAGECACHE_ACCT)
+
 /*
  * Try to free `nr_pages' of memory, system-wide, and return the number of
  * freed pages.
  * Modelled after shrink_all_memory()
  */
-unsigned long memcontrol_shrink_mapped_memory(unsigned long nr_pages,
-						struct container *container)
+unsigned long shrink_container_memory(unsigned int memory_type,
+			unsigned long nr_pages, struct container *container)
 {
 	unsigned long ret = 0;
 	int pass;
 	unsigned long nr_total_scanned = 0;
+	struct reclaim_state reclaim_state;

 	struct scan_control sc = {
 		.gfp_mask = GFP_KERNEL,
-		.may_swap = 0,
 		.swap_cluster_max = nr_pages,
 		.may_writepage = 1,
-		.container = container,
-		.may_swap = 1,
-		.swappiness = 100,
 	};

+ 	switch (memory_type) {
+ 		case RECLAIM_PAGECACHE_MEMORY:
+ 			sc.may_swap = 0;
+ 			sc.swappiness = 0; /* Do not swap, only pagecache reclaim */
+ 			sc.reclaim_pagecache_only = 1; /* Flag it */
+ 			break;
+
+ 		case RECLAIM_MAPPED_MEMORY:
+ 			sc.container = container;
+ 			sc.may_swap = 1;
+ 			sc.swappiness = 100; /* Do swap and free memory */
+ 			sc.reclaim_pagecache_only = 0; /* Flag it */
+ 			break;
+
+ 		default:
+ 			BUG();
+ 	}
+ 	current->reclaim_state = &reclaim_state;
+
+
 	/*
 	 * We try to shrink LRUs in 3 passes:
 	 * 0 = Reclaim from inactive_list only
-	 * 1 = Reclaim mapped (normal reclaim)
+ 	 * 1 = Reclaim from active list
+ 	 * 	(Mapped or pagecache pages depending on memory type)
 	 * 2 = 2nd pass of type 1
 	 */
 	for (pass = 0; pass < 3; pass++) {
@@ -1585,7 +1631,6 @@ unsigned long memcontrol_shrink_mapped_m

 		for (prio = DEF_PRIORITY; prio >= 0; prio--) {
 			unsigned long nr_to_scan = nr_pages - ret;
-
 			sc.nr_scanned = 0;
 			ret += shrink_all_zones(nr_to_scan, prio,
 						pass, 1, &sc);
@@ -1598,8 +1643,10 @@ unsigned long memcontrol_shrink_mapped_m
 		}
 	}
 out:
+	current->reclaim_state = NULL;
 	return ret;
 }
+
 #endif

 /* It's optimal to keep kswapds on the same CPUs as their memory, but
-
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