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On Fri, 23 Jan 2015, Julian Anastasov wrote:
> Hello,
>
> On Tue, 20 Jan 2015, Chris Caputo wrote:
> > My application consists of incoming TCP streams being load balanced to
> > servers which receive the feeds. These are long lived multi-gigabyte
> > streams, and so I believe the estimator's 2-second timer is fine. As an
> > example:
> >
> > # cat /proc/net/ip_vs_stats
> > Total Incoming Outgoing Incoming Outgoing
> > Conns Packets Packets Bytes Bytes
> > 9AB 58B7C17 0 1237CA2C325 0
> >
> > Conns/s Pkts/s Pkts/s Bytes/s Bytes/s
> > 1 387C 0 B16C4AE 0
>
> All other schedulers react and see different
> picture after every new connection. The worst example
> is WLC where slow-start mechanism is desired because
> idle server can be overloaded before the load is noticed
> properly. Even WRR accounts every connection in its state.
>
> Your setup may expect low number of connections per
> second but for other kind of setups sending all connections
> to same server for 2 seconds looks scary. In fact, what
> changes is the position, so we rotate only among the
> least loaded servers that look equally loaded but it is
> one server in the common case. And as our stats are per
> CPU and designed for human reading, it is difficult to
> read them often for other purposes. We need a good idea
> to solve this problem, so that we can have faster feedback
> after every scheduling.
This is exactly why my wlib/wlip code is a hybrid of wlc and rr. Last
location is saved, and search is started after it. Thus when traffic is
zero, round-robin occurs. When flows already exist, bursts of new
connections do choose poorly based on repeated use of last estimation, but
the complexity of working around that seems complex.
> > > May be not so useful idea: use sum of both directions
> > > or control it with svc->flags & IP_VS_SVC_F_SCHED_WLIB_xxx
> > > flags, see how "sh" scheduler supports flags. I.e.
> > > inbps + outbps.
> >
> > I see a user-mode option as increasing complexity. For example,
> > keepalived users would need to have keepalived patched to support the new
> > algorithm, due to flags, rather than just configuring "wlib" or "wlip" and
> > it just working.
>
> That is also true.
>
> > I think I'd rather see a wlob/wlop version for users that want to
> > load-balance based on outgoing bytes/packets, and a wlb/wlp version for
> > users that want them summed.
>
> ok
>
> > From: Chris Caputo <ccaputo@xxxxxxx>
> >
> > IPVS: Change inbps and outbps to 64-bits so that estimator handles faster
> > flows. Also increases maximum viewable at user level from ~2.15Gbits/s to
> > ~34.35Gbits/s.
>
> Yep, we are limited from u32 in user space structs.
> I have to think how to solve this problem.
>
> 1gbit => ~1.5 million pps
> 10gbit => ~15 million pps
> 100gbit => ~150 million pps
>
> > Signed-off-by: Chris Caputo <ccaputo@xxxxxxx>
> > ---
> > diff -uprN linux-3.19-rc5-stock/include/net/ip_vs.h
> > linux-3.19-rc5/include/net/ip_vs.h
> > --- linux-3.19-rc5-stock/include/net/ip_vs.h 2015-01-18
> > 06:02:20.000000000 +0000
> > +++ linux-3.19-rc5/include/net/ip_vs.h 2015-01-20 08:01:15.548177969
> > +0000
> > @@ -390,8 +390,8 @@ struct ip_vs_estimator {
> > u32 cps;
> > u32 inpps;
> > u32 outpps;
> > - u32 inbps;
> > - u32 outbps;
> > + u64 inbps;
> > + u64 outbps;
>
> Not sure, may be everything here should be u64 because
> we have shifted values. I'll need some days to investigate
> this issue...
>
> Regards
>
> --
> Julian Anastasov <ja@xxxxxx>
Sounds good and thanks!
Chris
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