On Wed, Jul 20, 2016 at 10:32:28PM +0000, Wiles, Keith wrote:
>
> > On Jul 20, 2016, at 3:16 PM, Neil Horman <nhorman at tuxdriver.com> wrote:
> >
> > On Wed, Jul 20, 2016 at 07:47:32PM +0000, Wiles, Keith wrote:
> >>
> >>> On Jul 20, 2016, at 12:48 PM, Neil Horman <nhorman at redhat.com> wrote:
> >>>
> >>> On Wed, Jul 20, 2016 at 07:40:49PM +0200, Thomas Monjalon wrote:
> >>>> 2016-07-20 13:09, Neil Horman:
> >>>>> From: Neil Horman <nhorman at redhat.com>
> >>>>>
> >>>>> John Mcnamara and I were discussing enhacing the validate_abi script to
> >>>>> build
> >>>>> the dpdk tree faster with multiple jobs. Theres no reason not to do
> >>>>> it, so this
> >>>>> implements that requirement. It uses a MAKE_JOBS variable that can be
> >>>>> set by
> >>>>> the user to limit the job count. By default the job count is set to
> >>>>> the number
> >>>>> of online cpus.
> >>>>
> >>>> Please could you use the variable name DPDK_MAKE_JOBS?
> >>>> This name is already used in scripts/test-build.sh.
> >>>>
> >>> Sure
> >>>
> >>>>> +if [ -z "$MAKE_JOBS" ]
> >>>>> +then
> >>>>> + # This counts the number of cpus on the system
> >>>>> + MAKE_JOBS=`lscpu -p=cpu | grep -v "#" | wc -l`
> >>>>> +fi
> >>>>
> >>>> Is lscpu common enough?
> >>>>
> >>> I'm not sure how to answer that. lscpu is part of the util-linux
> >>> package, which
> >>> is part of any base install. Theres a variant for BSD, but I'm not sure
> >>> how
> >>> common it is there.
> >>> Neil
> >>>
> >>>> Another acceptable default would be just "-j" without any number.
> >>>> It would make the number of jobs unlimited.
> >>
> >> I think the best is just use -j as it tries to use the correct number of
> >> jobs based on the number of cores, right?
> >>
> > -j with no argument (or -j 0), is sort of, maybe what you want. With
> > either of
> > those options, make will just issue jobs as fast as it processes
> > dependencies.
> > Dependent on how parallel the build is, that can lead to tons of waiting
> > process
> > (i.e. more than your number of online cpus), which can actually hurt your
> > build
> > time.
>
> I read the manual and looked at the code, which supports your statement. (I
> think I had some statement on stack overflow and the last time I believe
> anything on the internet :-) I have not seen a lot of differences in compile
> times with -j on my system. Mostly I suspect it is the number of paths in the
> dependency, cores and memory on the system.
>
> I have 72 lcores or 2 sockets, 18 cores per socket. Xeon 2.3Ghz cores.
>
> $ export RTE_TARGET=x86_64-native-linuxapp-gcc
>
> $ time make install T=${RTE_TARGET}
> real 0m59.445s user 0m27.344s sys 0m7.040s
>
> $ time make install T=${RTE_TARGET} -j
> real 0m26.584s user 0m14.380s sys 0m5.120s
>
> # Remove the x86_64-native-linuxapp-gcc
>
> $ time make install T=${RTE_TARGET} -j 72
> real 0m23.454s user 0m10.832s sys 0m4.664s
>
> $ time make install T=${RTE_TARGET} -j 8
> real 0m23.812s user 0m10.672s sys 0m4.276s
>
> cd x86_64-native-linuxapp-gcc
> $ make clean
> $ time make
> real 0m28.539s user 0m9.820s sys 0m3.620s
>
> # Do a make clean between each build.
>
> $ time make -j
> real 0m7.217s user 0m6.532s sys 0m2.332s
>
> $ time make -j 8
> real 0m8.256s user 0m6.472s sys 0m2.456s
>
> $ time make -j 72
> real 0m6.866s user 0m6.184s sys 0m2.216s
>
> Just the real time numbers in the following table.
>
> processes real Time depdirs
> no -j 59.4s Yes
> -j 8 23.8s Yes
> -j 72 23.5s Yes
> -j 26.5s Yes
>
> no -j 28.5s No
> -j 8 8.2s No
> -j 72 6.8s No
> -j 7.2s No
>
> Looks like the depdirs build time on my system:
> $ make clean -j
> $ rm .depdirs
> $ time make -j
> real 0m23.734s user 0m11.228s sys 0m4.844s
>
> About 16 seconds, which is not a lot of savings. Now the difference from no
> -j to -j is a lot, but the difference between -j and -j <cpu_count> is not a
> huge saving. This leads me back to over engineering the problem when ?-j?
> would work just as well here.
>
> Even on my MacBook Pro i7 system the difference is not that much 1m8s without
> depdirs build for -j in a VirtualBox with all 4 cores 8G RAM. Compared to
> 1m13s with -j 4 option.
>
> I just wonder if it makes a lot of sense to use cpuinfo in this given case if
> it turns out to be -j works with the 80% rule?
>
It may, but that seems to be reason to me to just set DPDK_MAKE_JOBS=0, and
you'll get that behavior
Neil
> On some other project with a lot more files like the FreeBSD or Linux distro,
> yes it would make a fair amount of real time difference.
>
> Keith
>
> >
> > While its fine in los of cases, its not always fine, and with this
> > implementation you can still opt in to that behavior by setting
> > DPDK_MAKE_JOBS=0
> >
> > Neil
> >
> >>
>
