GFS2: Adjust minimum hold times

PATCH New Bob Peterson 2 participants 2 messages Oct 17, 2012 – Oct 18, 2012 GFS2 file system

lore

Share & tools

lore

Bob Peterson

author

2012-10-17 17:34 UTC #0 lore raw

PATCH 1/1 GFS2: Adjust minimum hold times

Hi,

This patch adjusts the glock minimum hold times to smaller values. It also increases the hold time for each new holder record queued.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by Bob Peterson <[email protected]>

---

fs/gfs2/glock.c +6 -0

index e543871..beaa834 100644
@@ -985,6 +985,9 @@ fail:
 	trace_gfs2_glock_queue(gh, 1);
 	gfs2_glstats_inc(gl, GFS2_LKS_QCOUNT);
 	gfs2_sbstats_inc(gl, GFS2_LKS_QCOUNT);
+	/* For every new holder, add to the minimum hold time, up to the max */
+	gl->gl_hold_time = min(gl->gl_hold_time + GL_GLOCK_PERHOLDER_INCR,
+			       GL_GLOCK_MAX_HOLD);
 	if (likely(insert_pt == NULL)) {
 		list_add_tail(&gh->gh_list, &gl->gl_holders);
 		if (unlikely(gh->gh_flags & LM_FLAG_PRIORITY))

@@ -1079,6 +1082,9 @@ void gfs2_glock_dq(struct gfs2_holder *gh)
 	if (gh->gh_flags & GL_NOCACHE)
 		handle_callback(gl, LM_ST_UNLOCKED, 0);
 
+	/* One less holder, so adjust the minimum hold time down. */
+	gl->gl_hold_time = max(gl->gl_hold_time - GL_GLOCK_PERHOLDER_INCR,
+			       GL_GLOCK_MIN_HOLD);
 	list_del_init(&gh->gh_list);
 	if (find_first_holder(gl) == NULL) {
 		if (glops->go_unlock) {

fs/gfs2/glock.h +3 -2

index fd580b7..52068de 100644
@@ -113,11 +113,12 @@ enum {
 
 #define GLR_TRYFAILED		13
 
-#define GL_GLOCK_MAX_HOLD        (long)(HZ / 5)
-#define GL_GLOCK_DFT_HOLD        (long)(HZ / 5)
+#define GL_GLOCK_MAX_HOLD        (long)(HZ / 10)
+#define GL_GLOCK_DFT_HOLD        (long)(HZ / 10)
 #define GL_GLOCK_MIN_HOLD        (long)(10)
 #define GL_GLOCK_HOLD_INCR       (long)(HZ / 20)
 #define GL_GLOCK_HOLD_DECR       (long)(HZ / 40)
+#define GL_GLOCK_PERHOLDER_INCR  (long)(2)
 
 struct lm_lockops {
 	const char *lm_proto_name;

Steven Whitehouse

2012-10-18 13:27 UTC #1 lore raw

PATCH 1/1 GFS2: Adjust minimum hold times

Hi,

For all the patches in this set, I'm a bit concerned about the justification for making these changes. I'd like to be reasonably certain that we are not simply improving one workload running on one specific set of hardware at the expense of another, for example.

How much benefit do these actually give us? is it a lot, or just a small fraction on one particular workload?

I'd like to see some analysis to say why the smaller min hold time, etc is the right thing to do here. Or to maybe put it another way, if we were to ask how would we ideally adjust the min hold time to give maximum effect, given full knowledge of the system, is the answer something that we might implement given the information on the state of the system that is available on a single node?

If so then perhaps we should take a look at that rather than changing these constants around, unless there is a particularly large gain to be had here,

Steve.

Quoted 56 lines · Bob Peterson

Hi,