Re: [libvirt] [PATCH] virnetdevbandwidth: Compute quantum value

I've noticed couple of warning in dmesg while debugging something: [ 9683.973754] HTB: quantum of class 10001 is big. Consider r2q change. [ 9683.976460] HTB: quantum of class 10002 is big. Consider r2q change. I've read the HTB documentation and linux kernel code to find out what's wrong.

Basically we need to pass another argument to our

tc cmd line because the default computed by HTB does not always work in which case the warning message is printed out. You can read more details here: http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm#sharing Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/util/virnetdevbandwidth.c | 39 +++++++++++++++++++++++++++++++++++++++ tests/virnetdevbandwidthtest.c | 4 ++-- 2 files changed, 41 insertions(+), 2 deletions(-) diff --git a/src/util/virnetdevbandwidth.c b/src/util/virnetdevbandwidth.c index da3a0d3..a74cb1d 100644 --- a/src/util/virnetdevbandwidth.c +++ b/src/util/virnetdevbandwidth.c @@ -43,6 +43,36 @@ virNetDevBandwidthFree(virNetDevBandwidthPtr def) VIR_FREE(def); } +static int +virNetDevBandwidthSetOptimalQuantum(virCommandPtr cmd,

+ const virNetDevBandwidthRate *rate) +{ + const unsigned long long mtu = 1500; + unsigned long long r2q; + char *r2q_str; + + /* When two or more classes compete for unused bandwidth they are each + * given some number of bytes before serving other competing class. This + * number is called quantum. It's advised in HTB docs that the number + * should be equal to MTU. The class quantum is computed from its rate + * divided by global r2q parameter. However, if rate is too small the + * default value will not suffice and thus we must provide our own value. + * */ + + r2q = rate->average * 1024 / 8 / mtu; + if (!r2q) + r2q = 1; + + if (r2q != 10) {

+ if (virAsprintf(&r2q_str, "%llu", r2q) < 0) + return -1;

+ virCommandAddArgList(cmd, "quantum", r2q_str, NULL); + VIR_FREE(r2q_str); + } + + return 0; +} + /** * virNetDevBandwidthManipulateFilter: * @ifname: interface to operate on