A couple of 2.4.23-pre4 VM nits

[Shantanu Goel <sgoel01@yahoo.com>]

[-- Attachment #1: Type: text/plain, Size: 814 bytes --]

Hi Andrea,

The VM fixes perform rather well in my testing
(thanks!), but I noticed a couple of glitches that the
attached patch addresses.

1. max_scan is never decremented in shrink_cache().  I
am assuming this is a typo.

2. The second part of the patch makes sure that
inode/dentry caches are shrunk at least once every 5
secs.  On a machine with a heavy inode stat/directory
lookup load (e.g. NFS server), most of the memory
winds up sitting idle in unused inodes/dentry.  The
present code only reclaims these when a swap_out()
happens or shrink_caches() fails.  This can take a
while on a machine will very few mapped pages such as
an NFS server.

Thanks,
Shantanu

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[-- Attachment #2: vmscan.patch --]
[-- Type: application/octet-stream, Size: 2287 bytes --]

--- vmscan.c.~1~	2003-09-16 20:44:14.000000000 -0400
+++ vmscan.c	2003-09-17 18:23:03.000000000 -0400
@@ -364,6 +364,20 @@
 	return 0;
 }
 
+static void shrink_vfs_caches(int force, unsigned int gfp_mask)
+{
+	static unsigned long last_scan = 0;
+
+	if (force || time_after(jiffies, last_scan + 5*HZ)) {
+		shrink_dcache_memory(vm_vfs_scan_ratio, gfp_mask);
+		shrink_icache_memory(vm_vfs_scan_ratio, gfp_mask);
+#ifdef CONFIG_QUOTA
+		shrink_dqcache_memory(vm_vfs_scan_ratio, gfp_mask);
+#endif
+		last_scan = jiffies;
+	}
+}
+
 static void FASTCALL(refill_inactive(int nr_pages, zone_t * classzone));
 static int FASTCALL(shrink_cache(int nr_pages, zone_t * classzone, unsigned int gfp_mask, int * failed_swapout));
 static int shrink_cache(int nr_pages, zone_t * classzone, unsigned int gfp_mask, int * failed_swapout)
@@ -372,7 +386,7 @@
 	int max_scan = (classzone->nr_inactive_pages + classzone->nr_active_pages) / vm_cache_scan_ratio;
 	int max_mapped = vm_mapped_ratio * nr_pages;
 
-	while (max_scan && classzone->nr_inactive_pages && (entry = inactive_list.prev) != &inactive_list) {
+	while (--max_scan >= 0 && classzone->nr_inactive_pages && (entry = inactive_list.prev) != &inactive_list) {
 		struct page * page;
 
 		if (unlikely(current->need_resched)) {
@@ -516,11 +530,7 @@
 				if (nr_pages <= 0)
 					goto out;
 
-				shrink_dcache_memory(vm_vfs_scan_ratio, gfp_mask);
-				shrink_icache_memory(vm_vfs_scan_ratio, gfp_mask);
-#ifdef CONFIG_QUOTA
-				shrink_dqcache_memory(vm_vfs_scan_ratio, gfp_mask);
-#endif
+				shrink_vfs_caches(*failed_swapout, gfp_mask);
 
 				if (!*failed_swapout)
 					*failed_swapout = !swap_out(classzone);
@@ -614,6 +624,8 @@
 	if (nr_pages <= 0)
 		goto out;
 
+	shrink_vfs_caches(0, gfp_mask);
+
 	spin_lock(&pagemap_lru_lock);
 	refill_inactive(nr_pages, classzone);
 
@@ -638,11 +650,9 @@
 			nr_pages = shrink_caches(classzone, gfp_mask, nr_pages, &failed_swapout);
 			if (nr_pages <= 0)
 				return 1;
-			shrink_dcache_memory(vm_vfs_scan_ratio, gfp_mask);
-			shrink_icache_memory(vm_vfs_scan_ratio, gfp_mask);
-#ifdef CONFIG_QUOTA
-			shrink_dqcache_memory(vm_vfs_scan_ratio, gfp_mask);
-#endif
+
+			shrink_vfs_caches(1, gfp_mask);
+
 			if (!failed_swapout)
 				failed_swapout = !swap_out(classzone);
 		} while (--tries);