[PATCH] Represent dirty_*_centisecs as jiffies internally

Make that the internal values for: /proc/sys/vm/dirty_writeback_centisecs /proc/sys/vm/dirty_expire_centisecs are stored as jiffies instead of centiseconds. Let the sysctl interface do the conversions with full precision using clock_t_to_jiffies, instead of doing overflow-sensitive on-the-fly conversions every time the values are used. Cons: apparent precision loss if HZ is not a multiple of 100, because of conversion back and forth. This is a common problem for all sysctl values that use proc_dointvec_userhz_jiffies. (There is only one other in-tree use, in net/core/neighbour.c.) Signed-off-by: Bart Samwel <bart@samwel.tk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] Represent dirty_*_centisecs as jiffies internally
Make that the internal values for: /proc/sys/vm/dirty_writeback_centisecs /proc/sys/vm/dirty_expire_centisecs are stored as jiffies instead of centiseconds. Let the sysctl interface do the conversions with full precision using clock_t_to_jiffies, instead of doing overflow-sensitive on-the-fly conversions every time the values are used. Cons: apparent precision loss if HZ is not a multiple of 100, because of conversion back and forth. This is a common problem for all sysctl values that use proc_dointvec_userhz_jiffies. (There is only one other in-tree use, in net/core/neighbour.c.) Signed-off-by: Bart Samwel <bart@samwel.tk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Bart Samwel · Linus Torvalds
1 parent 36f574135e
Showing 3 changed files with 19 additions and 19 deletions Side-by-side Diff
include/linux/writeback.h
kernel/sysctl.c
mm/page-writeback.c
@@ -88,8 +88,8 @@
 /* These are exported to sysctl. */
 extern int dirty_background_ratio;
 extern int vm_dirty_ratio;
-extern int dirty_writeback_centisecs;
-extern int dirty_expire_centisecs;
+extern int dirty_writeback_interval;
+extern int dirty_expire_interval;
 extern int block_dump;
 extern int laptop_mode;
  
@@ -742,18 +742,18 @@
 	{
 		.ctl_name	= VM_DIRTY_WB_CS,
 		.procname	= "dirty_writeback_centisecs",
-		.data		= &dirty_writeback_centisecs,
-		.maxlen		= sizeof(dirty_writeback_centisecs),
+		.data		= &dirty_writeback_interval,
+		.maxlen		= sizeof(dirty_writeback_interval),
 		.mode		= 0644,
 		.proc_handler	= &dirty_writeback_centisecs_handler,
 	},
 	{
 		.ctl_name	= VM_DIRTY_EXPIRE_CS,
 		.procname	= "dirty_expire_centisecs",
-		.data		= &dirty_expire_centisecs,
-		.maxlen		= sizeof(dirty_expire_centisecs),
+		.data		= &dirty_expire_interval,
+		.maxlen		= sizeof(dirty_expire_interval),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec,
+		.proc_handler	= &proc_dointvec_userhz_jiffies,
 	},
 	{
 		.ctl_name	= VM_NR_PDFLUSH_THREADS,
@@ -75,12 +75,12 @@
  * The interval between `kupdate'-style writebacks, in centiseconds
  * (hundredths of a second)
  */
-int dirty_writeback_centisecs = 5 * 100;
+int dirty_writeback_interval = 5 * HZ;
  
 /*
  * The longest number of centiseconds for which data is allowed to remain dirty
  */
-int dirty_expire_centisecs = 30 * 100;
+int dirty_expire_interval = 30 * HZ;
  
 /*
  * Flag that makes the machine dump writes/reads and block dirtyings.
@@ -380,8 +380,8 @@
  * just walks the superblock inode list, writing back any inodes which are
  * older than a specific point in time.
  *
- * Try to run once per dirty_writeback_centisecs.  But if a writeback event
- * takes longer than a dirty_writeback_centisecs interval, then leave a
+ * Try to run once per dirty_writeback_interval.  But if a writeback event
+ * takes longer than a dirty_writeback_interval interval, then leave a
  * one-second gap.
  *
  * older_than_this takes precedence over nr_to_write.  So we'll only write back
  
@@ -406,9 +406,9 @@
 	sync_supers();
  
 	get_writeback_state(&wbs);
-	oldest_jif = jiffies - (dirty_expire_centisecs * HZ) / 100;
+	oldest_jif = jiffies - dirty_expire_interval;
 	start_jif = jiffies;
-	next_jif = start_jif + (dirty_writeback_centisecs * HZ) / 100;
+	next_jif = start_jif + dirty_writeback_interval;
 	nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
 			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
 	while (nr_to_write > 0) {
@@ -425,7 +425,7 @@
 	}
 	if (time_before(next_jif, jiffies + HZ))
 		next_jif = jiffies + HZ;
-	if (dirty_writeback_centisecs)
+	if (dirty_writeback_interval)
 		mod_timer(&wb_timer, next_jif);
 }
  
  
@@ -435,11 +435,11 @@
 int dirty_writeback_centisecs_handler(ctl_table *table, int write,
 		struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
 {
-	proc_dointvec(table, write, file, buffer, length, ppos);
-	if (dirty_writeback_centisecs) {
+	proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
+	if (dirty_writeback_interval) {
 		mod_timer(&wb_timer,
-			jiffies + (dirty_writeback_centisecs * HZ) / 100);
-	} else {
+			jiffies + dirty_writeback_interval);
+		} else {
 		del_timer(&wb_timer);
 	}
 	return 0;
@@ -544,7 +544,7 @@
 		if (vm_dirty_ratio <= 0)
 			vm_dirty_ratio = 1;
 	}
-	mod_timer(&wb_timer, jiffies + (dirty_writeback_centisecs * HZ) / 100);
+	mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
 	set_ratelimit();
 	register_cpu_notifier(&ratelimit_nb);
 }
...	...	@@ -88,8 +88,8 @@
88	88	/* These are exported to sysctl. */
89	89	extern int dirty_background_ratio;
90	90	extern int vm_dirty_ratio;
91		-extern int dirty_writeback_centisecs;
92		-extern int dirty_expire_centisecs;
	91	+extern int dirty_writeback_interval;
	92	+extern int dirty_expire_interval;
93	93	extern int block_dump;
94	94	extern int laptop_mode;
95	95
...	...	@@ -742,18 +742,18 @@
742	742	{
743	743	.ctl_name = VM_DIRTY_WB_CS,
744	744	.procname = "dirty_writeback_centisecs",
745		- .data = &dirty_writeback_centisecs,
746		- .maxlen = sizeof(dirty_writeback_centisecs),
	745	+ .data = &dirty_writeback_interval,
	746	+ .maxlen = sizeof(dirty_writeback_interval),
747	747	.mode = 0644,
748	748	.proc_handler = &dirty_writeback_centisecs_handler,
749	749	},
750	750	{
751	751	.ctl_name = VM_DIRTY_EXPIRE_CS,
752	752	.procname = "dirty_expire_centisecs",
753		- .data = &dirty_expire_centisecs,
754		- .maxlen = sizeof(dirty_expire_centisecs),
	753	+ .data = &dirty_expire_interval,
	754	+ .maxlen = sizeof(dirty_expire_interval),
755	755	.mode = 0644,
756		- .proc_handler = &proc_dointvec,
	756	+ .proc_handler = &proc_dointvec_userhz_jiffies,
757	757	},
758	758	{
759	759	.ctl_name = VM_NR_PDFLUSH_THREADS,
...	...	@@ -75,12 +75,12 @@
75	75	* The interval between `kupdate'-style writebacks, in centiseconds
76	76	* (hundredths of a second)
77	77	*/
78		-int dirty_writeback_centisecs = 5 * 100;
	78	+int dirty_writeback_interval = 5 * HZ;
79	79
80	80	/*
81	81	* The longest number of centiseconds for which data is allowed to remain dirty
82	82	*/
83		-int dirty_expire_centisecs = 30 * 100;
	83	+int dirty_expire_interval = 30 * HZ;
84	84
85	85	/*
86	86	* Flag that makes the machine dump writes/reads and block dirtyings.
...	...	@@ -380,8 +380,8 @@
380	380	* just walks the superblock inode list, writing back any inodes which are
381	381	* older than a specific point in time.
382	382	*
383		- * Try to run once per dirty_writeback_centisecs. But if a writeback event
384		- * takes longer than a dirty_writeback_centisecs interval, then leave a
	383	+ * Try to run once per dirty_writeback_interval. But if a writeback event
	384	+ * takes longer than a dirty_writeback_interval interval, then leave a
385	385	* one-second gap.
386	386	*
387	387	* older_than_this takes precedence over nr_to_write. So we'll only write back
388	388
...	...	@@ -406,9 +406,9 @@
406	406	sync_supers();
407	407
408	408	get_writeback_state(&wbs);
409		- oldest_jif = jiffies - (dirty_expire_centisecs * HZ) / 100;
	409	+ oldest_jif = jiffies - dirty_expire_interval;
410	410	start_jif = jiffies;
411		- next_jif = start_jif + (dirty_writeback_centisecs * HZ) / 100;
	411	+ next_jif = start_jif + dirty_writeback_interval;
412	412	nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
413	413	(inodes_stat.nr_inodes - inodes_stat.nr_unused);
414	414	while (nr_to_write > 0) {
...	...	@@ -425,7 +425,7 @@
425	425	}
426	426	if (time_before(next_jif, jiffies + HZ))
427	427	next_jif = jiffies + HZ;
428		- if (dirty_writeback_centisecs)
	428	+ if (dirty_writeback_interval)
429	429	mod_timer(&wb_timer, next_jif);
430	430	}
431	431
432	432
...	...	@@ -435,11 +435,11 @@
435	435	int dirty_writeback_centisecs_handler(ctl_table *table, int write,
436	436	struct file file, void __user buffer, size_t length, loff_t ppos)
437	437	{
438		- proc_dointvec(table, write, file, buffer, length, ppos);
439		- if (dirty_writeback_centisecs) {
	438	+ proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
	439	+ if (dirty_writeback_interval) {
440	440	mod_timer(&wb_timer,
441		- jiffies + (dirty_writeback_centisecs * HZ) / 100);
442		- } else {
	441	+ jiffies + dirty_writeback_interval);
	442	+ } else {
443	443	del_timer(&wb_timer);
444	444	}
445	445	return 0;
...	...	@@ -544,7 +544,7 @@
544	544	if (vm_dirty_ratio <= 0)
545	545	vm_dirty_ratio = 1;
546	546	}
547		- mod_timer(&wb_timer, jiffies + (dirty_writeback_centisecs * HZ) / 100);
	547	+ mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
548	548	set_ratelimit();
549	549	register_cpu_notifier(&ratelimit_nb);
550	550	}