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authorSteven Whitehouse <swhiteho@redhat.com>2013-02-01 20:36:03 +0000
committerSteven Whitehouse <swhiteho@redhat.com>2013-02-01 20:36:03 +0000
commit4506a519f2a76775e6c236f44d50e9f79a7d3434 (patch)
tree20b1e8e26fcb2bbe09b9589ed38183f6b0f6a4d4 /fs/gfs2
parent4513899092b3254b3539f92a65d2839afa1d50f6 (diff)
downloadlinux-4506a519f2a76775e6c236f44d50e9f79a7d3434.tar.gz
GFS2: Split glock lru processing into two parts
The intent here is to split the processing of the glock lru list into two parts, so that the selection of glocks and the disposal are separate functions. The plan is then, that further updates can then be made to these functions in the future to improve the selection of glocks and also the efficiency of glock disposal. The new feature which this patch brings is sorting the glocks to be disposed of into glock number (and thus also disk block number) order. Not all glocks will need i/o in order to dispose of them, but some will, and at least we'll generate mostly disk block order i/o now. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2')
-rw-r--r--fs/gfs2/glock.c90
1 files changed, 67 insertions, 23 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 3ad8fd36f8d..cf351554673 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -30,6 +30,7 @@
#include <linux/rculist_bl.h>
#include <linux/bit_spinlock.h>
#include <linux/percpu.h>
+#include <linux/list_sort.h>
#include "gfs2.h"
#include "incore.h"
@@ -1376,50 +1377,93 @@ void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
gfs2_glock_put(gl);
}
+static int glock_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+ struct gfs2_glock *gla, *glb;
+
+ gla = list_entry(a, struct gfs2_glock, gl_lru);
+ glb = list_entry(b, struct gfs2_glock, gl_lru);
+
+ if (gla->gl_name.ln_number > glb->gl_name.ln_number)
+ return 1;
+ if (gla->gl_name.ln_number < glb->gl_name.ln_number)
+ return -1;
+
+ return 0;
+}
+
+/**
+ * gfs2_dispose_glock_lru - Demote a list of glocks
+ * @list: The list to dispose of
+ *
+ * Disposing of glocks may involve disk accesses, so that here we sort
+ * the glocks by number (i.e. disk location of the inodes) so that if
+ * there are any such accesses, they'll be sent in order (mostly).
+ *
+ * Must be called under the lru_lock, but may drop and retake this
+ * lock. While the lru_lock is dropped, entries may vanish from the
+ * list, but no new entries will appear on the list (since it is
+ * private)
+ */
+
+static void gfs2_dispose_glock_lru(struct list_head *list)
+__releases(&lru_lock)
+__acquires(&lru_lock)
+{
+ struct gfs2_glock *gl;
+
+ list_sort(NULL, list, glock_cmp);
+
+ while(!list_empty(list)) {
+ gl = list_entry(list->next, struct gfs2_glock, gl_lru);
+ list_del_init(&gl->gl_lru);
+ clear_bit(GLF_LRU, &gl->gl_flags);
+ gfs2_glock_hold(gl);
+ spin_unlock(&lru_lock);
+ spin_lock(&gl->gl_spin);
+ if (demote_ok(gl))
+ handle_callback(gl, LM_ST_UNLOCKED, 0);
+ WARN_ON(!test_and_clear_bit(GLF_LOCK, &gl->gl_flags));
+ smp_mb__after_clear_bit();
+ if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
+ gfs2_glock_put_nolock(gl);
+ spin_unlock(&gl->gl_spin);
+ spin_lock(&lru_lock);
+ }
+}
+
/**
* gfs2_scan_glock_lru - Scan the LRU looking for locks to demote
* @nr: The number of entries to scan
*
+ * This function selects the entries on the LRU which are able to
+ * be demoted, and then kicks off the process by calling
+ * gfs2_dispose_glock_lru() above.
*/
static void gfs2_scan_glock_lru(int nr)
{
struct gfs2_glock *gl;
- int may_demote;
- int nr_skipped = 0;
LIST_HEAD(skipped);
+ LIST_HEAD(dispose);
spin_lock(&lru_lock);
while(nr && !list_empty(&lru_list)) {
gl = list_entry(lru_list.next, struct gfs2_glock, gl_lru);
- list_del_init(&gl->gl_lru);
- clear_bit(GLF_LRU, &gl->gl_flags);
- atomic_dec(&lru_count);
/* Test for being demotable */
if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
- gfs2_glock_hold(gl);
- spin_unlock(&lru_lock);
- spin_lock(&gl->gl_spin);
- may_demote = demote_ok(gl);
- if (may_demote) {
- handle_callback(gl, LM_ST_UNLOCKED, 0);
- nr--;
- }
- clear_bit(GLF_LOCK, &gl->gl_flags);
- smp_mb__after_clear_bit();
- if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
- gfs2_glock_put_nolock(gl);
- spin_unlock(&gl->gl_spin);
- spin_lock(&lru_lock);
+ list_move(&gl->gl_lru, &dispose);
+ atomic_dec(&lru_count);
+ nr--;
continue;
}
- nr_skipped++;
- list_add(&gl->gl_lru, &skipped);
- set_bit(GLF_LRU, &gl->gl_flags);
+
+ list_move(&gl->gl_lru, &skipped);
}
list_splice(&skipped, &lru_list);
- atomic_add(nr_skipped, &lru_count);
+ if (!list_empty(&dispose))
+ gfs2_dispose_glock_lru(&dispose);
spin_unlock(&lru_lock);
}