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SubjectAtrocious icache/dcache in 2.4.2
Date
Hi,

Here is a patch that prunes unused, clean inodes from the icache
faster. I have previously checked out cleaning the unused dirty
icache entries from the the same place in kswapd but did not find
it to be much a win.

This code does the following. It factors prune_icache to use,
prune_unused_icache to actually prune the list. This makes it
simple to add a shrink_unused_icache_memory routine which gets
plugged into the kswapd loop. The result is the icache is kept
smaller.

fast_prune.diff
-----
--- 2.4.4-pre7/include/linux/dcache.h Thu Apr 26 12:57:47 2001
+++ linux/include/linux/dcache.h Fri Apr 27 18:17:20 2001
@@ -176,6 +176,7 @@

/* icache memory management (defined in linux/fs/inode.c) */
extern void shrink_icache_memory(int, int);
+extern void shrink_unused_icache_memory(int);
extern void prune_icache(int);

/* only used at mount-time */
--- 2.4.4-pre7/mm/vmscan.c Fri Apr 27 11:36:04 2001
+++ linux/mm/vmscan.c Fri Apr 27 18:33:07 2001
@@ -953,6 +953,11 @@
*/
refill_inactive_scan(DEF_PRIORITY, 0);

+ /*
+ * Free unused inodes.
+ */
+ shrink_unused_icache_memory(GFP_KSWAPD);
+
/* Once a second, recalculate some VM stats. */
if (time_after(jiffies, recalc + HZ)) {
recalc = jiffies;
--- 2.4.4-pre7/fs/inode.c Thu Apr 26 12:49:33 2001
+++ linux/fs/inode.c Fri Apr 27 18:54:25 2001
@@ -540,16 +540,16 @@
!inode_has_buffers(inode))
#define INODE(entry) (list_entry(entry, struct inode, i_list))

-void prune_icache(int goal)
+/*
+ * Called with inode lock held, returns with it released.
+ */
+int prune_unused_icache(int goal)
{
LIST_HEAD(list);
struct list_head *entry, *freeable = &list;
- int count = 0, synced = 0;
+ int count = 0;
struct inode * inode;

- spin_lock(&inode_lock);
-
-free_unused:
entry = inode_unused.prev;
while (entry != &inode_unused)
{
@@ -577,19 +577,27 @@

dispose_list(freeable);

+ return count;
+}
+
+/*
+ * A goal of zero frees everything
+ */
+void prune_icache(int goal)
+{
+ spin_lock(&inode_lock);
+ goal -= prune_unused_icache(goal);
+
/*
* If we freed enough clean inodes, avoid writing
- * dirty ones. Also giveup if we already tried to
- * sync dirty inodes.
+ * dirty ones.
*/
- if (!goal || synced)
+ if (!goal)
return;

- synced = 1;
-
spin_lock(&inode_lock);
try_to_sync_unused_inodes();
- goto free_unused;
+ prune_unused_icache(goal);
}

void shrink_icache_memory(int priority, int gfp_mask)
@@ -611,6 +619,20 @@

prune_icache(count);
kmem_cache_shrink(inode_cachep);
+}
+
+void shrink_unused_icache_memory(int gfp_mask)
+{
+ /*
+ * Nasty deadlock avoidance..
+ */
+ if (!(gfp_mask & __GFP_IO))
+ return;
+
+ if (spin_trylock(&inode_lock)) {
+ prune_unused_icache(0);
+ kmem_cache_shrink(inode_cachep);
+ }
}

/*
-----
Comments?

Ed Tomlinson <tomlins@cam.org>
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