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authorNeilBrown <neilb@suse.de>2006-06-26 00:27:37 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 09:58:37 -0700
commit16f17b39f385212b73278a76d482cdcaaebe6c02 (patch)
treeb7b79b380257e7438516a8b38cd9fbd33284f64f
parent9443a1d1f72c688646278c06d0a9a3c79e895325 (diff)
[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>
-rw-r--r--Documentation/md.txt9
-rw-r--r--drivers/md/md.c54
2 files changed, 61 insertions, 2 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt
index 03a13c462cf2..b19978e035fc 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -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}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 30a93d64921e..ad576ad2ca76 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -44,6 +44,7 @@
#include <linux/suspend.h>
#include <linux/poll.h>
#include <linux/mutex.h>
+#include <linux/ctype.h>
#include <linux/init.h>
@@ -1978,6 +1979,54 @@ 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)
{
struct mdk_personality *p = mddev->pers;
@@ -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);
}
}