> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Tan, Jianfeng > Sent: Wednesday, March 09, 2016 1:53 PM > To: Panu Matilainen; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH] eal: add option --avail-cores to detect lcores > > > > On 3/9/2016 9:05 PM, Panu Matilainen wrote: > > On 03/08/2016 07:38 PM, Tan, Jianfeng wrote: > >> Hi Panu, > >> > >> On 3/8/2016 4:54 PM, Panu Matilainen wrote: > >>> On 03/04/2016 12:05 PM, Jianfeng Tan wrote: > >>>> This patch adds option, --avail-cores, to use lcores which are > >>>> available > >>>> by calling pthread_getaffinity_np() to narrow down detected cores > >>>> before > >>>> parsing coremask (-c), corelist (-l), and coremap (--lcores). > >>>> > >>>> Test example: > >>>> $ taskset 0xc0000 ./examples/helloworld/build/helloworld \ > >>>> --avail-cores -m 1024 > >>>> > >>>> Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com> > >>>> Acked-by: Neil Horman <nhorman at tuxdriver.com> > >>> > >>> Hmm, to me this sounds like something that should be done always so > >>> there's no need for an option. Or if there's a chance it might do the > >>> wrong thing in some rare circumstance then perhaps there should be a > >>> disabler option instead? > >> > >> Thanks for comments. > >> > >> Yes, there's a use case that we cannot handle. > >> > >> If we make it as default, DPDK applications may fail to start, when user > >> specifies a core in isolcpus and its parent process (say bash) has a > >> cpuset affinity that excludes isolcpus. Originally, DPDK applications > >> just blindly do pthread_setaffinity_np() and it always succeeds because > >> it always has root privilege to change any cpu affinity. > >> > >> Now, if we do the checking in rte_eal_cpu_init(), those lcores will be > >> flagged as undetected (in my older implementation) and leads to failure. > >> To make it correct, we would always add "taskset mask" (or other ways) > >> before DPDK application cmd lines. > >> > >> How do you think? > > > > I still think it sounds like something that should be done by default > > and maybe be overridable with some flag, rather than the other way > > around. Another alternative might be detecting the cores always but if > > running as root, override but with a warning. > > For your second solution, only root can setaffinity to isolcpus? > Your first solution seems like a promising way for me. > > > > > But I dont know, just wondering. To look at it from another angle: why > > would somebody use this new --avail-cores option and in what > > situation, if things "just work" otherwise anyway? > > For DPDK applications, the most common case to initialize DPDK is like > this: "$dpdk-app [options for DPDK] -- [options for app]", so users need > to specify which cores to run and how much hugepages are used. Suppose > we need this dpdk-app to run in a container, users already give those > information when they build up the cgroup for it to run inside, this > option or this patch is to make DPDK more smart to discover how much > resource will be used. Make sense?
But then, all we need might be just a script that would extract this information from the system and form a proper cmdline parameter for DPDK? Konstantin > > Thanks, > Jianfeng > > > > > > - Panu - > >
