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Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo |
Date: |
Fri, 6 Mar 2015 18:30:22 +0000 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* zhanghailiang (address@hidden) wrote:
> On 2015/3/5 21:31, Dr. David Alan Gilbert (git) wrote:
> >From: "Dr. David Alan Gilbert" <address@hidden>
>
> Hi Dave,
>
> >
> >Hi,
> > I'm getting COLO running on a couple of our machines here
> >and wanted to see what was actually going on, so I merged
> >in my recent rolling-stats code:
> >
> >http://lists.gnu.org/archive/html/qemu-devel/2015-03/msg00648.html
> >
> >with the following patch, and now I get on the primary side,
> >info migrate shows me:
> >
> >capabilities: xbzrle: off rdma-pin-all: off auto-converge: off zero-blocks:
> >off colo: on
> >Migration status: colo
> >total time: 0 milliseconds
> >colo checkpoint (ms): Min/Max: 0, 10000 Mean: -1.1415868e-13 (Weighted:
> >4.3136025e-158) Count: 4020 Values: address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden, address@hidden
> >colo paused time (ms): Min/Max: 55, 2789 Mean: 63.9 (Weighted: 76.243584)
> >Count: 4019 Values: address@hidden, address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden
> >colo checkpoint size: Min/Max: 18351, 2.1731606e+08 Mean: 150096.4
> >(Weighted: 127195.56) Count: 4020 Values: address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden, address@hidden,
> >address@hidden, address@hidden, address@hidden, address@hidden
> >
> >which suggests I've got a problem with the packet comparison; but that's
> >a separate issue I'll look at.
> >
>
> There is an obvious mistake we have made in proxy, the macro
> 'IPS_UNTRACKED_BIT' in colo-patch-for-kernel.patch should be 14,
> so please fix it before do the follow test. Sorry for this low-grade mistake,
> we should do full test before issue it. ;)
No, that's OK; we all make them.
However, that didn't cure my problem; but after a bit of experimentation I now
have
COLO working pretty well; thanks for the help!
1) I had to disable IPv6 in the guest; it doesn't look like the
conntrack is coping with IPv6 ICMPV6, and on our test network
we're getting a few 10s of those each second, so it's constant
miscompares (they seem to be neighbour broadcasts and multicast
stuff).
2) It looks like virtio-net is sending ARPs - possibly every time
that a snapshot is loaded; it's not the 'qemu' announce-self code,
(I added some debug there and it's not being called); and ARPs
cause a miscompare - so you get a continuous streem of miscompares
because a miscompare triggers a new snapshot, that sends more ARPs.
I solved this by switching to e1000.
3) The other problem with virtio is it's occasionally triggering a
'virtio: error trying to map MMIO memory' from qemu; I'm not sure
why, the state COLO sends over should always be consistent.
4) With the e1000 setup; connections are generally fairly responsive,
but sshing into the guest takes *ages* (10s of seconds). I'm not sure
why, because a curl to a web server seems OK (less than a second)
and once the ssh is open it's pretty responsive.
5) I've seen one instance of;
'qemu-system-x86_64: block/raw-posix.c:836: handle_aiocb_rw: Assertion `p
- buf == aiocb->aio_nbytes' failed.'
on the primary side.
Stats for a mostly idle guest are now showing:
colo checkpoint (ms): Min/Max: 0, 10004 Mean: 1592.1 (Weighted: 1806.214)
Count: 227 Values: address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden, address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden
colo paused time (ms): Min/Max: 58, 2975 Mean: 90.3 (Weighted: 94.109752)
Count: 227 Values: address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden, address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden
colo checkpoint size: Min/Max: 212252, 1.9241972e+08 Mean: 5569622.6 (Weighted:
4826386.5) Count: 227 Values: address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden, address@hidden, address@hidden, address@hidden,
address@hidden, address@hidden
So, one checkpoint every ~1.5 seconds; that's just with an
ssh connected and a script doing a 'curl' to it's http
repeatedly. Running 'top' on the ssh with a fast refresh
brings the checkpoints much faster; I guess that's because
the output of top is quite random.
> To be honest, the proxy part in github is not integrated, we have cut it just
> for easy review and understand, so there may be some mistakes.
Yes, that's OK; and I've had a few kernel crashes; normally
when the qemu crashes, the kernel doesn't really like it;
but that's OK, I'm sure it will get better.
I added the following to make my debug easier; which is how
I found the IPv6 problem.
diff --git a/xt_PMYCOLO.c b/xt_PMYCOLO.c
index 9e50b62..13c0b48 100644
--- a/xt_PMYCOLO.c
+++ b/xt_PMYCOLO.c
@@ -1072,7 +1072,7 @@ resolve_master_ct(struct sk_buff *skb, unsigned int
dataoff,
h = nf_conntrack_find_get(&init_net, NF_CT_DEFAULT_ZONE, &tuple);
if (h == NULL) {
- pr_dbg("can't find master's ct for slaver packet\n");
+ pr_dbg("can't find master's ct for slaver packet (pf/l3num=%d
protonum=%d)\n", l3num, protonum);
return NULL;
}
@@ -1092,7 +1092,7 @@ nf_conntrack_slaver_in(u_int8_t pf, unsigned int hooknum,
/* rcu_read_lock()ed by nf_hook_slow */
l3proto = __nf_ct_l3proto_find(pf);
if (l3proto->get_l4proto(skb, skb_network_offset(skb), &dataoff,
&protonum) <= 0) {
- pr_dbg("slaver: l3proto not prepared to track yet or error
occurred\n");
+ pr_dbg("slaver: l3proto not prepared to track yet or error
occurred (pf=%d)\n", pf);
NF_CT_STAT_INC_ATOMIC(&init_net, error);
NF_CT_STAT_INC_ATOMIC(&init_net, invalid);
goto out;
>
> Thanks,
> zhanghailiang
Thanks,
Dave
>
>
> >Dave
> >
> >Dr. David Alan Gilbert (1):
> > COLO: Add primary side rolling statistics
> >
> > hmp.c | 12 ++++++++++++
> > include/migration/migration.h | 3 +++
> > migration/colo.c | 15 +++++++++++++++
> > migration/migration.c | 30 ++++++++++++++++++++++++++++++
> > qapi-schema.json | 11 ++++++++++-
> > 5 files changed, 70 insertions(+), 1 deletion(-)
> >
>
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [RFC 0/1] Rolling stats on colo, Dr. David Alan Gilbert (git), 2015/03/05
- [Qemu-devel] [RFC 1/1] COLO: Add primary side rolling statistics, Dr. David Alan Gilbert (git), 2015/03/05
- Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo, zhanghailiang, 2015/03/05
- Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo, zhanghailiang, 2015/03/10
- Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo, Dr. David Alan Gilbert, 2015/03/11
- Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo, zhanghailiang, 2015/03/11
- Re: [Qemu-devel] [RFC 0/1] Rolling stats on colo, Dr. David Alan Gilbert, 2015/03/11