Date: Sun, 30 Jan 2011 15:16:03 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Robby Sun <robbysun@gmail.com> Cc: freebsd-performance@freebsd.org, Julian Elischer <julian@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, Stefan Lambrev <stefan.lambrev@moneybookers.com> Subject: Re: Interrupt performance Message-ID: <20110130121603.GN18170@zxy.spb.ru> In-Reply-To: <AANLkTimP4RybWKY_Qhuv6mi0%2BVNVASJUL3rxy-eoy6z_@mail.gmail.com> References: <20110128143355.GD18170@zxy.spb.ru> <22E77EED-6455-4164-9115-BBD359EC8CA6@moneybookers.com> <20110128161035.GF18170@zxy.spb.ru> <CDBFAB7F-1EBC-4B3A-B2F5-6162DD58A93D@moneybookers.com> <4D42F87C.7020909@freebsd.org> <20110128172516.GG18170@zxy.spb.ru> <20110129070205.Q7034@besplex.bde.org> <20110128215215.GJ18170@zxy.spb.ru> <AANLkTimP4RybWKY_Qhuv6mi0%2BVNVASJUL3rxy-eoy6z_@mail.gmail.com>
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On Sat, Jan 29, 2011 at 09:55:06PM -0800, Robby Sun wrote:
> I'd like to suggest that you use the same bit-width for 'Dummy' as that for
> 'count', and initialize it to 0, so as to ensure that it won't overflow.
I don't use value of Dummy, overflow don't meaning.
> -Robby
>
> On Fri, Jan 28, 2011 at 1:52 PM, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote:
>
> > On Sat, Jan 29, 2011 at 07:52:11AM +1100, Bruce Evans wrote:
> >
> > > >> there are of course several possible answers, including:
> > > >>
> > > >> 1/ Sometimes BSD and Linux report things differently. Linux may or may
> > not
> > > >> account for the lowest level interrupt tie the same as BSD
> > > >
> > > > But I see only 20% idle on FreeBSD and 80% idle on Linux.
> > >
> > > The time must be counted somewhere, so when it is not properly accounted
> > > to packet handling, and nothing much else is running, it is accounted to
> > > idle.
> > >
> > > To see how much CPU is actually available, run something else and see how
> > > fast it runs. A simple counting loops works well on UP systems.
> >
> > ===
> > #include <stdio.h>
> > #include <sys/time.h>
> >
> > int Dummy;
> >
> > int
> > main(int argc, char *argv[])
> > {
> > long int count,i,dt;
> > struct timeval st,et;
> >
> > count = atol(argv[1]);
> >
> > gettimeofday(&st, NULL);
> > for(i=count;i;i--) Dummy++;
> > gettimeofday(&et, NULL);
> > dt = (et.tv_sec-st.tv_sec)*1000000 + et.tv_usec-st.tv_usec;
> > printf("Elapsed %d us\n",dt);
> > }
> > ===
> >
> > This is ok?
> >
> > ./loop 2000000000
> >
> > FreeBSD
> > 1 process: Elapsed 7554193 us
> > 2 process: Elapsed 14493692 us
> > netperf + 1 process: Elapsed 21403644 us
> >
> > Linux
> > 1 process: Elapsed 7524843 us
> > 2 process: Elapsed 14995866 us
> > netperf + 1 process: Elapsed 14107670 us
> >
> >
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