[Devel] [PATCH RHEL7 COMMIT] vziolimit: port diff-ubc-iolimit-precharge-dirty-pages-opensource

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-123.1.2-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-123.1.2.vz7.4.9
------>
commit e6d640dd11fe7f1fc172f81d4a2e61d1d198eaf0
Author: Dmitry Monakhov <dmonakhov at openvz.org>
Date:   Tue May 5 13:44:40 2015 +0400

    vziolimit: port diff-ubc-iolimit-precharge-dirty-pages-opensource
    
    https://jira.sw.ru/browse/PSBM-20104
    
    Signed-off-by: Dmitry Monakhov <dmonakhov at openvz.org>
---
 kernel/ve/vziolimit.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/kernel/ve/vziolimit.c b/kernel/ve/vziolimit.c
index 7ff2854..19dd7ad 100644
--- a/kernel/ve/vziolimit.c
+++ b/kernel/ve/vziolimit.c
@@ -120,6 +120,35 @@ static unsigned long iolimit_timeout(struct iolimit *iolimit)
 			throttle_timeout(&iolimit->iops, now));
 }
 
+static void iolimit_balance_dirty(struct iolimit *iolimit,
+				  struct user_beancounter *ub,
+				  unsigned long write_chunk)
+{
+	struct throttle *th = &iolimit->throttle;
+	unsigned long flags, dirty, state;
+
+	if (!th->speed)
+		return;
+
+	/* can be non-atomic on i386, but ok. this just hint. */
+	state = th->state >> PAGE_SHIFT;
+	dirty = ub_stat_get(ub, dirty_pages) + write_chunk;
+	/* protect agains ub-stat percpu drift */
+	if (dirty + UB_STAT_BATCH * num_possible_cpus()	< state)
+		return;
+	/* get exact value of for smooth throttling */
+	dirty = ub_stat_get_exact(ub, dirty_pages) + write_chunk;
+	if (dirty < state)
+		return;
+
+	spin_lock_irqsave(&ub->ub_lock, flags);
+	/* precharge dirty pages */
+	throttle_charge(th, (long long)dirty << PAGE_SHIFT);
+	/* set dirty_exceeded for smooth throttling */
+	ub->dirty_exceeded = 1;
+	spin_unlock_irqrestore(&ub->ub_lock, flags);
+}
+
 static int iolimit_virtinfo(struct vnotifier_block *nb,
 		unsigned long cmd, void *arg, int old_ret)
 {
@@ -170,6 +199,9 @@ static int iolimit_virtinfo(struct vnotifier_block *nb,
 			if (timeout)
 				return NOTIFY_FAIL;
 			break;
+		case VIRTINFO_IO_BALANCE_DIRTY:
+			iolimit_balance_dirty(iolimit, ub, (unsigned long)arg);
+			break;
 	}
 
 	return NOTIFY_OK;