Re: [libvirt] problem with outbound limiting

On 08/11/2011 08:07 AM, Upendra Moturi wrote: > Thanks for your reply. > > The patch it appears still has problem. > I have changed only mtu value as 2kb instead of burst value in the > network.c file > > With average as 2048 , burst as 2048 and peak 2048 > scp copied at 30-40KB/s All test I did were with the patch applied. I saw the throughput collapsing yesterday at 2Mb mtu.

I generated a file using dd if=/dev/urandom of=testfile bs=1024 count=409600 I did the same test you did with 2048 without specifying a specific model of ethernet card and reach 1.9MB/s using scp'ing towards remote machine. When specifying <model type='virtio'/> I also get 1.9MB/s as result. > With average as 4096 , burst as 4096 and peak 4096 > scp copied at same 30-40KB/s > With these numbers and using the virtio model I ended up getting a throughput of 3.8Mb/s. The host is a 3.0.0 Linux kernel. Here's the command line output of the tc command inspecting the tap interface of the VM (vnet0). # tc filter show dev vnet0 root filter parent ffff: protocol ip pref 49152 u32 filter parent ffff: protocol ip pref 49152 u32 fh 800: ht divisor 1 filter parent ffff: protocol ip pref 49152 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid :1 match 00000000/00000000 at 12 police 0x5b rate 32768Kbit burst 4Mb mtu 2Kb action drop overhead 0b ref 1 bind 1 Maybe someone else can verify as well. Stefan > where as earlier it was 1 MB/s.(without patch) > > On Wed, Aug 10, 2011 at 9:16 PM, Stefan Berger > <stefanb(a)linux.vnet.ibm.com&gt; wrote: >> On 08/10/2011 11:20 AM, Eric Blake wrote: >>> On 08/10/2011 09:04 AM, Stefan Berger wrote: >>>> On 08/10/2011 02:55 AM, Upendra Moturi wrote: >>>> >>>> Hi, >>>> >>>> does this patch solve your problem? I am setting the MTU to fixed >>>> 2kb. >>>> Doing tests with scp seems to indicate that this improved the >>>> situation >>>> -- at least for me. >>>> >>>> Stefan >>>> >>>> Signed-off-by: Stefan Berger&lt;stefanb(a)linux.vnet.ibm.com&gt; >>>> >>>> --- >>>> src/util/network.c | 16 ++++++++-------- >>>> 1 file changed, 8 insertions(+), 8 deletions(-) >>>> >>>> Index: libvirt-acl/src/util/network.c >>>> =================================================================== >>>> --- libvirt-acl.orig/src/util/network.c >>>> +++ libvirt-acl/src/util/network.c >>>> @@ -1156,8 +1156,8 @@ virBandwidthEnable(virBandwidthPtr bandw >>>> >>>> virCommandFree(cmd); >>>> cmd = virCommandNew(TC); >>>> - virCommandAddArgList(cmd,"class", "add", "dev", iface, "parent", >>>> - "1:", "classid", "1:1", "htb", NULL); >>>> + virCommandAddArgList(cmd,"class", "add", "dev", iface, "parent", >>>> + "1:", "classid", "1:1", "htb", NULL); >>>> virCommandAddArgList(cmd, "rate", average, NULL); >>> This hunk was just indentation; you should push the whitespace >>> changes as >>> a separate commit (and can push that now, under the trivial rule, >>> without >>> needing further review). [It doesn't help matters that thunderbird >>> botched >>> the whitespace in my reply] >>> >>>> @@ -1202,7 +1202,7 @@ virBandwidthEnable(virBandwidthPtr bandw >>>> virCommandAddArgList(cmd, "filter", "add", "dev", iface, "parent", >>>> "ffff:", "protocol", "ip", "u32", "match", "ip", >>>> "src", "0.0.0.0/0", "police", "rate", average, >>>> - "burst", burst, "mtu", burst, "drop", "flowid", >>>> + "burst", burst, "mtu", "2kb", "drop", "flowid", >>>> ":1", NULL); >>> Here's the meat of the proposed patch. Is 2kb always valid, or >>> will we >>> run into problems on NICs that insist on traditional limits near >>> the 1518 >>> mark? Should it be user-configurable? I'm reluctant to ACK this >>> without a >>> bit more understanding of why 2kb works, as well as feedback on >>> test results >>> with the patch in place. >>> >> Yes, I am not an exper on tc. I have seen examples with the mtu >> being set to >> '1' for dropping icmp traffic for example. So if a VM produces >> smaller than >> 2kb packets, which on traditional networks it probably should, then the >> packets should go through. We could also leave out the mtu parameter >> above >> and it would go to 2kb by default. Check via >> >> tc filter show dev<ifname> root >> >> The 2kb parameter doesn't explain why 2MB doesn't work, though. >> Even if this wasn't the final fix, it at least 'improves the >> situation' (for >> me). >> >> Stefan >> >> >> > > -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list