Re: [libvirt] problem with outbound limiting

On 08/11/2011 09:39 AM, Stefan Berger wrote: > > 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. Let me clarify : Yesterday I saw the throughput collapse without the patch applied.   Stefan > > 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 -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list