[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>
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index beaef5c..6095659 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -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;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 32b48e8..817ba25 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -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,
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 945559f..e7910799 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -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);
}