[pve-devel] [PATCH] qemu : add drive-mirror sleep patches

[Alexandre Derumier]

Currently when drive-mirror is starting,
the vm and qmp it's hanging on bitmap scanning phase (mainly with raw, nfs and block raw driver).

This patch do regular pause between each iteration

The initial patch from qemu mailing is working,but pause time is really too short,
so we still hang qmp hangs and qemu big slowdown.

I increase it to SLICE_TIME, which is 100ms by default

Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 debian/patches/mirror-sleep.patch           | 58 +++++++++++++++++++++++++++++
 debian/patches/series                       |  2 +
 qemu-kvm/debian/patches/mirror-sleep2.patch | 28 ++++++++++++++
 3 files changed, 88 insertions(+)
 create mode 100644 debian/patches/mirror-sleep.patch
 create mode 100644 qemu-kvm/debian/patches/mirror-sleep2.patch

diff --git a/debian/patches/mirror-sleep.patch b/debian/patches/mirror-sleep.patch
new file mode 100644
index 0000000..37dc939
--- /dev/null
+++ b/debian/patches/mirror-sleep.patch
@@ -0,0 +1,58 @@
+From 2540abec85433596dd04640b14f75ceb13bbb342 Mon Sep 17 00:00:00 2001
+From: Fam Zheng <famz at redhat.com>
+Date: Wed, 13 May 2015 11:11:13 +0800
+Subject: [PATCH] block/mirror: Sleep periodically during bitmap scanning
+
+Before, we only yield after initializing dirty bitmap, where the QMP
+command would return. That may take very long, and guest IO will be
+blocked.
+
+Add sleep points like the later mirror iterations.
+
+Signed-off-by: Fam Zheng <famz at redhat.com>
+Reviewed-by: Wen Congyang <wency at cn.fujitsu.com>
+Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
+Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
+---
+ block/mirror.c | 13 ++++++++++++-
+ 1 file changed, 12 insertions(+), 1 deletion(-)
+
+diff --git a/block/mirror.c b/block/mirror.c
+index 4056164..0a05971 100644
+--- a/block/mirror.c
++++ b/block/mirror.c
+@@ -432,11 +432,23 @@ static void coroutine_fn mirror_run(void *opaque)
+     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
+     mirror_free_init(s);
+ 
++    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+     if (!s->is_none_mode) {
+         /* First part, loop on the sectors and initialize the dirty bitmap.  */
+         BlockDriverState *base = s->base;
+         for (sector_num = 0; sector_num < end; ) {
+             int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
++            int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
++
++            if (now - last_pause_ns > SLICE_TIME) {
++                last_pause_ns = now;
++                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
++            }
++
++            if (block_job_is_cancelled(&s->common)) {
++                goto immediate_exit;
++            }
++
+             ret = bdrv_is_allocated_above(bs, base,
+                                           sector_num, next - sector_num, &n);
+ 
+@@ -455,7 +467,6 @@ static void coroutine_fn mirror_run(void *opaque)
+     }
+ 
+     bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi);
+-    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+     for (;;) {
+         uint64_t delay_ns = 0;
+         int64_t cnt;
+-- 
+2.1.4
+
diff --git a/debian/patches/series b/debian/patches/series
index 1105537..a018473 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -33,3 +33,5 @@ add-qmp-get-link-status.patch
 0001-friendlier-ai_flag-hints-for-ipv6-hosts.patch
 0001-vvfat-add-a-label-option.patch
 jemalloc.patch
+mirror-sleep.patch
+mirror-sleep2.patch
diff --git a/qemu-kvm/debian/patches/mirror-sleep2.patch b/qemu-kvm/debian/patches/mirror-sleep2.patch
new file mode 100644
index 0000000..e1b59db
--- /dev/null
+++ b/qemu-kvm/debian/patches/mirror-sleep2.patch
@@ -0,0 +1,28 @@
+From d1ca17e6bfcf8292b85474cc871e015088672df4 Mon Sep 17 00:00:00 2001
+From: Alexandre Derumier <aderumier at odiso.com>
+Date: Wed, 1 Jul 2015 05:07:06 +0200
+Subject: [PATCH] increase block_job_sleep_ns time to SLICE_TIME
+
+current value 0 is really too short to avoid qmp hangs
+
+Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
+---
+ block/mirror.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/block/mirror.c b/block/mirror.c
+index 0a05971..2711249 100644
+--- a/block/mirror.c
++++ b/block/mirror.c
+@@ -442,7 +442,7 @@ static void coroutine_fn mirror_run(void *opaque)
+ 
+             if (now - last_pause_ns > SLICE_TIME) {
+                 last_pause_ns = now;
+-                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
++                block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, SLICE_TIME);
+             }
+ 
+             if (block_job_is_cancelled(&s->common)) {
+-- 
+2.1.4
+
-- 
2.1.4