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[PATCH] md: increase the delay before marking metadata clean, and make it configurable 

When a md array has been idle (no writes) for 20msecs it is marked as 'clean'.
 This delay turns out to be too short for some real workloads.  So increase it
to 200msec (the time to update the metadata should be a tiny fraction of that)
and make it sysfs-configurable.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown 2006-06-26 00:27:37 -07:00 committed by Linus Torvalds
parent 9443a1d1f7
commit 16f17b39f3
2 changed files with 61 additions and 2 deletions
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9
Documentation/md.txt
View File

@ -207,6 +207,15 @@ All md devices contain:
available. It will then appear at md/dev-XXX (depending on the
name of the device) and further configuration is then possible.
safe_mode_delay
When an md array has seen no write requests for a certain period
of time, it will be marked as 'clean'. When another write
request arrive, the array is marked as 'dirty' before the write
commenses. This is known as 'safe_mode'.
The 'certain period' is controlled by this file which stores the
period as a number of seconds. The default is 200msec (0.200).
Writing a value of 0 disables safemode.
sync_speed_min
sync_speed_max
This are similar to /proc/sys/dev/raid/speed_limit_{min,max}

54
drivers/md/md.c
View File

@ -44,6 +44,7 @@
#include <linux/suspend.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/ctype.h>
#include <linux/init.h>
@ -1977,6 +1978,54 @@ static void analyze_sbs(mddev_t * mddev)
}
static ssize_t
safe_delay_show(mddev_t *mddev, char *page)
{
int msec = (mddev->safemode_delay*1000)/HZ;
return sprintf(page, "%d.%03d\n", msec/1000, msec%1000);
}
static ssize_t
safe_delay_store(mddev_t *mddev, const char *cbuf, size_t len)
{
int scale=1;
int dot=0;
int i;
unsigned long msec;
char buf[30];
char *e;
/* remove a period, and count digits after it */
if (len >= sizeof(buf))
return -EINVAL;
strlcpy(buf, cbuf, len);
buf[len] = 0;
for (i=0; i<len; i++) {
if (dot) {
if (isdigit(buf[i])) {
buf[i-1] = buf[i];
scale *= 10;
}
buf[i] = 0;
} else if (buf[i] == '.') {
dot=1;
buf[i] = 0;
}
}
msec = simple_strtoul(buf, &e, 10);
if (e == buf || (*e && *e != '\n'))
return -EINVAL;
msec = (msec * 1000) / scale;
if (msec == 0)
mddev->safemode_delay = 0;
else {
mddev->safemode_delay = (msec*HZ)/1000;
if (mddev->safemode_delay == 0)
mddev->safemode_delay = 1;
}
return len;
}
static struct md_sysfs_entry md_safe_delay =
__ATTR(safe_mode_delay, 0644,safe_delay_show, safe_delay_store);
static ssize_t
level_show(mddev_t *mddev, char *page)
{
@ -2433,6 +2482,7 @@ static struct attribute *md_default_attrs[] = {
&md_size.attr,
&md_metadata.attr,
&md_new_device.attr,
&md_safe_delay.attr,
NULL,
};
@ -2708,7 +2758,7 @@ static int do_md_run(mddev_t * mddev)
mddev->safemode = 0;
mddev->safemode_timer.function = md_safemode_timeout;
mddev->safemode_timer.data = (unsigned long) mddev;
mddev->safemode_delay = (20 * HZ)/1000 +1; /* 20 msec delay */
mddev->safemode_delay = (200 * HZ)/1000 +1; /* 200 msec delay */
mddev->in_sync = 1;
ITERATE_RDEV(mddev,rdev,tmp)
@ -4594,7 +4644,7 @@ void md_write_end(mddev_t *mddev)
if (atomic_dec_and_test(&mddev->writes_pending)) {
if (mddev->safemode == 2)
md_wakeup_thread(mddev->thread);
else
else if (mddev->safemode_delay)
mod_timer(&mddev->safemode_timer, jiffies + mddev->safemode_delay);
}
}