"Michael S. Tsirkin" <mst at redhat.com> wrote on 12/08/2014 12:18:50 PM:> From: "Michael S. Tsirkin" <mst at redhat.com> > To: David Miller <davem at davemloft.net> > Cc: Razya Ladelsky/Haifa/IBM at IBMIL, kvm at vger.kernel.org, Alex > Glikson/Haifa/IBM at IBMIL, Eran Raichstein/Haifa/IBM at IBMIL, Yossi > Kuperman1/Haifa/IBM at IBMIL, Joel Nider/Haifa/IBM at IBMIL, > abel.gordon at gmail.com, linux-kernel at vger.kernel.org, > netdev at vger.kernel.org, virtualization at lists.linux-foundation.org > Date: 12/08/2014 12:18 PM > Subject: Re: [PATCH] vhost: Add polling mode > > On Mon, Aug 11, 2014 at 12:46:21PM -0700, David Miller wrote: > > From: "Michael S. Tsirkin" <mst at redhat.com> > > Date: Sun, 10 Aug 2014 21:45:59 +0200 > > > > > On Sun, Aug 10, 2014 at 11:30:35AM +0300, Razya Ladelsky wrote: > > ... > > > And, did your tests actually produce 100% load on both host CPUs? > > ... > > > > Michael, please do not quote an entire patch just to ask a one line > > question. > > > > I truly, truly, wish it was simpler in modern email clients to delete > > the unrelated quoted material because I bet when people do this they > > are simply being lazy. > > > > Thank you. > > Lazy - mea culpa, though I'm using mutt so it isn't even hard. > > The question still stands: the test results are only valid > if CPU was at 100% in all configurations. > This is the reason I generally prefer it when people report > throughput divided by CPU (power would be good too but it still > isn't easy for people to get that number). >Hi Michael, Sorry for the delay, had some problems with my mailbox, and I realized just now that my reply wasn't sent. The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or not. The vhost thread utilized less than 100% (of the other cpu) when polling was disabled. Enabling polling increased its utilization to 100% (in which case both cpus were 100% utilized).> -- > MST >
On Tue, Aug 12, 2014 at 01:57:05PM +0300, Razya Ladelsky wrote:> "Michael S. Tsirkin" <mst at redhat.com> wrote on 12/08/2014 12:18:50 PM: > > > From: "Michael S. Tsirkin" <mst at redhat.com> > > To: David Miller <davem at davemloft.net> > > Cc: Razya Ladelsky/Haifa/IBM at IBMIL, kvm at vger.kernel.org, Alex > > Glikson/Haifa/IBM at IBMIL, Eran Raichstein/Haifa/IBM at IBMIL, Yossi > > Kuperman1/Haifa/IBM at IBMIL, Joel Nider/Haifa/IBM at IBMIL, > > abel.gordon at gmail.com, linux-kernel at vger.kernel.org, > > netdev at vger.kernel.org, virtualization at lists.linux-foundation.org > > Date: 12/08/2014 12:18 PM > > Subject: Re: [PATCH] vhost: Add polling mode > > > > On Mon, Aug 11, 2014 at 12:46:21PM -0700, David Miller wrote: > > > From: "Michael S. Tsirkin" <mst at redhat.com> > > > Date: Sun, 10 Aug 2014 21:45:59 +0200 > > > > > > > On Sun, Aug 10, 2014 at 11:30:35AM +0300, Razya Ladelsky wrote: > > > ... > > > > And, did your tests actually produce 100% load on both host CPUs? > > > ... > > > > > > Michael, please do not quote an entire patch just to ask a one line > > > question. > > > > > > I truly, truly, wish it was simpler in modern email clients to delete > > > the unrelated quoted material because I bet when people do this they > > > are simply being lazy. > > > > > > Thank you. > > > > Lazy - mea culpa, though I'm using mutt so it isn't even hard. > > > > The question still stands: the test results are only valid > > if CPU was at 100% in all configurations. > > This is the reason I generally prefer it when people report > > throughput divided by CPU (power would be good too but it still > > isn't easy for people to get that number). > > > > Hi Michael, > > Sorry for the delay, had some problems with my mailbox, and I realized > just now that > my reply wasn't sent. > The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or > not. > The vhost thread utilized less than 100% (of the other cpu) when polling > was disabled. > Enabling polling increased its utilization to 100% (in which case both > cpus were 100% utilized).Hmm this means the testing wasn't successful then, as you said: The idea was to get it 100% loaded, so we can see that the polling is getting it to produce higher throughput. in fact here you are producing more throughput but spending more power to produce it, which can have any number of explanations besides polling improving the efficiency. For example, increasing system load might disable host power management.> > -- > > MST > >
> > > > Hi Michael, > > > > Sorry for the delay, had some problems with my mailbox, and I realized> > just now that > > my reply wasn't sent. > > The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or> > not. > > The vhost thread utilized less than 100% (of the other cpu) whenpolling> > was disabled. > > Enabling polling increased its utilization to 100% (in which case both> > cpus were 100% utilized). > > Hmm this means the testing wasn't successful then, as you said: > > The idea was to get it 100% loaded, so we can see that the polling is > getting it to produce higher throughput. > > in fact here you are producing more throughput but spending more power > to produce it, which can have any number of explanations besides polling > improving the efficiency. For example, increasing system load might > disable host power management. >Hi Michael, I re-ran the tests, this time with the "turbo mode" and "C-states" features off. No Polling: 1 VM running netperf (msg size 64B): 1107 Mbits/sec Polling: 1 VM running netperf (msg size 64B): 1572 Mbits/sec As you can see from the new results, the numbers are lower, but relatively (polling on/off) there's no change. Thank you, Razya> > > > -- > > > MST > > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >