[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [libvirt] [PATCH 2/2] libxl: support vif outgoing bandwidth QoS
On 01/07/2016 07:48 AM, Michal Privoznik wrote: > On 29.12.2015 02:09, Jim Fehlig wrote: >> The libxl_device_nic structure supports specifying an outgoing rate >> limit based on a time interval and bytes allowed per interval. In xl >> config a rate limit is specified as "<RATE>/s@<INTERVAL>". INTERVAL >> is optional and defaults to 50ms. >> >> libvirt expresses outgoing limits by average (required), peak, burst, >> and floor attributes in units of KB/s. This patch supports the outgoing >> bandwidth limit by converting the average KB/s to bytes per interval >> based on the same default interval (50ms) used by xl. >> >> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx> >> --- >> src/libxl/libxl_conf.c | 39 +++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 39 insertions(+) >> >> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c >> index 23c74e7..6320421 100644 >> --- a/src/libxl/libxl_conf.c >> +++ b/src/libxl/libxl_conf.c >> @@ -1093,6 +1093,7 @@ libxlMakeNic(virDomainDefPtr def, >> { >> bool ioemu_nic = def->os.type == VIR_DOMAIN_OSTYPE_HVM; >> virDomainNetType actual_type = virDomainNetGetActualType(l_nic); >> + virNetDevBandwidthPtr actual_bw; >> >> /* TODO: Where is mtu stored? >> * >> @@ -1206,6 +1207,44 @@ libxlMakeNic(virDomainDefPtr def, >> #endif >> } >> >> + /* >> + * Set bandwidth. >> + * From $xen-sources/docs/misc/xl-network-configuration.markdown: >> + * >> + * >> + * Specifies the rate at which the outgoing traffic will be limited to. >> + * The default if this keyword is not specified is unlimited. >> + * >> + * The rate may be specified as "<RATE>/s" or optionally >> "<RATE>/s@<INTERVAL>". >> + * >> + * `RATE` is in bytes and can accept suffixes: >> + * GB, MB, KB, B for bytes. >> + * Gb, Mb, Kb, b for bits. >> + * `INTERVAL` is in microseconds and can accept suffixes: ms, us, s. >> + * It determines the frequency at which the vif transmission credit >> + * is replenished. The default is 50ms. >> + >> + * Vif rate limiting is credit-based. It means that for "1MB/s@20ms", >> + * the available credit will be equivalent of the traffic you would have >> + * done at "1MB/s" during 20ms. This will results in a credit of 20,000 >> + * bytes replenished every 20,000 us. >> + * >> + * >> + * libvirt doesn't support the notion of rate limiting over an interval. >> + * Similar to xl's behavior when interval is not specified, set a >> default >> + * interval of 50ms and calculate the number of bytes per interval based >> + * on the specified average bandwidth. >> + */ >> + actual_bw = virDomainNetGetActualBandwidth(l_nic); >> + if (actual_bw && actual_bw->out && actual_bw->out->average) { >> + uint64_t bytes_per_sec = actual_bw->out->average * 1024; >> + uint64_t bytes_per_interval = >> + (((uint64_t) bytes_per_sec * 50000UL) / 1000000UL); >> + >> + x_nic->rate_bytes_per_interval = bytes_per_interval; >> + x_nic->rate_interval_usecs = 50000UL; >> + } >> + > Interesting. I'd expect: > > x_nic->rate_bytes_per_interval = bytes_per_sec; > x_nic->rate_interval_usecs = 1000*1000; For the most part I mimicked the Xen code and wanted to stick with the default interval of 50ms, which has been the default for a long time. It is even mentioned in some old RHEL5 docs https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Virtualization/sect-Virtualization-Tips_and_tricks-Limit_network_bandwidth_for_a_Xen_guest.html BTW, here is the Xen code that inspired this logic http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=tools/libxl/libxlu_vif.c;h=0665e624dc178a6ca8058e04a7baacaf1475bd37;hb=HEAD#l131 rate_bytes_per_interval is set to (bytes/s * interval us)/1000000us I guess we are saying the same thing, you're just setting interval to 1s (thus rate_bytes_per_interval == bytes_per_sec) instead of the historical 50ms :-). > > I mean, if I understood the xl way of rate limiting correctly, one says > how much bytes can be sent for how long. so for 1MB/s I'd expect to send > 1024*1024 bytes each second. > > Or am I missing something? Does the above explanation make sense? I might be missing something :-). CC'd a few Xen tools maintainer just in case. Regards, Jim _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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