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SubjectRe: [PATCH 00/12] IO-less dirty throttling v7
Hi Sedat,

> Please revert the last commit. It's not necessary anyway.
>
> commit 84a9890ddef487d9c6d70934c0a2addc65923bcf
> Author: Wu Fengguang <fengguang.wu@intel.com>
> Date: Sat Apr 16 18:38:41 2011 -0600
>
> writeback: scale dirty proportions period with writeout bandwidth
>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

Please do revert that commit, because I found a sleep-inside-spinlock
bug with it. Here is the fixed one (but you don't have to track this
optional patch).

Thanks,
Fengguang
---
Subject: writeback: scale dirty proportions period with writeout bandwidth
Date: Sat Apr 16 18:38:41 CST 2011

CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

--- linux-next.orig/mm/page-writeback.c 2011-04-17 20:52:13.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-04-18 07:57:01.000000000 +0800
@@ -121,20 +121,13 @@ static struct prop_descriptor vm_complet
static struct prop_descriptor vm_dirties;

/*
- * couple the period to the dirty_ratio:
+ * couple the period to global write throughput:
*
- * period/2 ~ roundup_pow_of_two(dirty limit)
+ * period/2 ~ roundup_pow_of_two(write IO throughput)
*/
static int calc_period_shift(void)
{
- unsigned long dirty_total;
-
- if (vm_dirty_bytes)
- dirty_total = vm_dirty_bytes / PAGE_SIZE;
- else
- dirty_total = (vm_dirty_ratio * determine_dirtyable_memory()) /
- 100;
- return 2 + ilog2(dirty_total - 1);
+ return 2 + ilog2(default_backing_dev_info.avg_write_bandwidth);
}

/*
@@ -143,6 +136,13 @@ static int calc_period_shift(void)
static void update_completion_period(void)
{
int shift = calc_period_shift();
+
+ if (shift > PROP_MAX_SHIFT)
+ shift = PROP_MAX_SHIFT;
+
+ if (abs(shift - vm_completions.pg[0].shift) <= 1)
+ return;
+
prop_change_shift(&vm_completions, shift);
prop_change_shift(&vm_dirties, shift);
}
@@ -180,7 +180,6 @@ int dirty_ratio_handler(struct ctl_table

ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret == 0 && write && vm_dirty_ratio != old_ratio) {
- update_completion_period();
vm_dirty_bytes = 0;
}
return ret;
@@ -196,7 +195,6 @@ int dirty_bytes_handler(struct ctl_table

ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
if (ret == 0 && write && vm_dirty_bytes != old_bytes) {
- update_completion_period();
vm_dirty_ratio = 0;
}
return ret;
@@ -1044,6 +1042,8 @@ snapshot:
bdi->bw_time_stamp = now;
unlock:
spin_unlock(&dirty_lock);
+ if (gbdi->bw_time_stamp == now)
+ update_completion_period();
}

static unsigned long max_pause(struct backing_dev_info *bdi,

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