I wondered something similar. The crazy patterns usually happen on columns of the 2D matrix and as it is column major, it does loosely fit the idea (most of the time).
I will play some more (though I'm fed up with it now). JB -----Original Message----- From: Brice Goglin <brice.gog...@inria.fr> Sent: 29 January 2019 10:35 To: Biddiscombe, John A. <biddi...@cscs.ch>; Hardware locality user list <hwloc-users@lists.open-mpi.org> Subject: Re: [hwloc-users] unusual memory binding results Crazy idea: 512 pages could be replaced with a single 2MB huge page. You're not requesting huge pages in your allocation but some systems have transparent huge pages enabled by default (e.g. RHEL https://access.redhat.com/solutions/46111) This could explain why 512 pages get allocated on the same node, but it wouldn't explain crazy patterns you've seen in the past. Brice Le 29/01/2019 à 10:23, Biddiscombe, John A. a écrit : > I simplified things and instead of writing to a 2D array, I allocate a 1D > array of bytes and touch pages in a linear fashion. > Then I call syscall(NR)move_pages, ....) and retrieve a status array for each > page in the data. > > When I allocate 511 pages and touch alternate pages on alternate numa > nodes > > Numa page binding 511 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 > 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 > > but as soon as I increase to 512 pages, it breaks. > > Numa page binding 512 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > On the 8 numa node machine it sometimes gives the right answer even with 512 > pages. > > Still baffled > > JB > > -----Original Message----- > From: hwloc-users <hwloc-users-boun...@lists.open-mpi.org> On Behalf Of > Biddiscombe, John A. > Sent: 28 January 2019 16:14 > To: Brice Goglin <brice.gog...@inria.fr> > Cc: Hardware locality user list <hwloc-users@lists.open-mpi.org> > Subject: Re: [hwloc-users] unusual memory binding results > > Brice > >> Can you print the pattern before and after thread 1 touched its pages, or >> even in the middle ? >> It looks like somebody is touching too many pages here. > Experimenting with different threads touching one or more pages, I get > unpredicatable results > > here on the 8 numa node device, the result is perfect. I am only > allowing thread 3 and 7 to write a single memory location > > get_numa_domain() 8 Domain Numa pattern > -------- > -------- > -------- > 3------- > -------- > -------- > -------- > 7------- > ============================ > > ============================ > Contents of memory locations > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 26 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 63 0 0 0 0 0 0 0 > ============================ > > you can see that core 26 (numa domain 3) wrote to memory, and so did > core 63 (domain 8) > > Now I run it a second time and look, its rubbish > > get_numa_domain() 8 Domain Numa pattern > 3------- > 3------- > 3------- > 3------- > 3------- > 3------- > 3------- > 3------- > ============================ > > ============================ > Contents of memory locations > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 26 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 63 0 0 0 0 0 0 0 > ============================ > > after allowing the data to be read by a random thread > > 37777777 > 37777777 > 37777777 > 37777777 > 37777777 > 37777777 > 37777777 > 37777777 > > I'm baffled. > > JB > > _______________________________________________ > hwloc-users mailing list > hwloc-users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/hwloc-users _______________________________________________ hwloc-users mailing list hwloc-users@lists.open-mpi.org https://lists.open-mpi.org/mailman/listinfo/hwloc-users
