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[PATCH] Represent dirty_*_centisecs as jiffies internally

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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>
This commit is contained in:
Bart Samwel 2006-03-24 03:15:48 -08:00 committed by Linus Torvalds
parent 36f574135e
commit f6ef943813
3 changed files with 19 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
include/linux/writeback.h
View file

@ -88,8 +88,8 @@ void throttle_vm_writeout(void);
/* 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;

10
kernel/sysctl.c
View file

@ -742,18 +742,18 @@ static ctl_table vm_table[] = {
{
.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,

24
mm/page-writeback.c
View file

@ -75,12 +75,12 @@ int vm_dirty_ratio = 40;
* 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 @@ static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
* 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 @@ static void wb_kupdate(unsigned long arg)
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 @@ static void wb_kupdate(unsigned long arg)
}
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 @@ static void wb_kupdate(unsigned long arg)
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 @@ void __init page_writeback_init(void)
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);
}