2016-05-19 10:25, Tan, Jianfeng: > On 5/18/2016 8:46 PM, David Marchand wrote: > > On Wed, Mar 9, 2016 at 2:05 PM, Panu Matilainen <pmatilai at redhat.com> > > wrote: > >> On 03/08/2016 07:38 PM, Tan, Jianfeng wrote: > >>> 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. > >> > >> 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? > > +1 and I don't even see why we should have an option to disable this, > > since taskset would do the job. > > > > Looking at your special case, if the user did set an isolcpus option > > for another use, with no -c/-l, I understand the dpdk application > > won't care too much about it. > > So, this seems like somehow rude to the rest of the system and unwanted. > > The case you mentioned above is not the case I mean. But you make your > point about this one. > The case I originally mean: user sets an isolcpus option for DPDK > applications. Originally, DPDK apps would be started without any > problem. But for now, fail to start them because the required cores are > excluded before -c/-l. As per your comments following, we can add a > warning message (or should we quit on this situation?). But it indeed > has an effect on old users (they should changed to use "taskset > ./dpdk_app ..."). Do you think it's a problem?
There is no activity on this patch. Jianfeng, do not hesitate to ping if needed. Should we class this patch as "changes requested"?
