On Mon, 26 Apr 2010 16:00:41 -0500 Jack Steiner <steiner@xxxxxxx> wrote: > We have observed several workloads running on multi-node systems where > memory is assigned unevenly across the nodes in the system. There are > numerous reasons for this but one is the round-robin rotor in > cpuset_mem_spread_node(). > > For example, a simple test that writes a multi-page file will allocate pages > on nodes 0 2 4 6 ... Odd nodes are skipped. (Sometimes it allocates on > odd nodes & skips even nodes). > > An example is shown below. The program "lfile" writes a file consisting of > 10 pages. The program then mmaps the file & uses get_mempolicy(..., > MPOL_F_NODE) to determine the nodes where the file pages were allocated. > The output is shown below: > > # ./lfile > allocated on nodes: 2 4 6 0 1 2 6 0 2 > > > > There is a single rotor that is used for allocating both file pages & slab > pages. Writing the file allocates both a data page & a slab page > (buffer_head). This advances the RR rotor 2 nodes for each page > allocated. > > A quick confirmation seems to confirm this is the cause of the uneven > allocation: > > # echo 0 >/dev/cpuset/memory_spread_slab > # ./lfile > allocated on nodes: 6 7 8 9 0 1 2 3 4 5 > > > This patch introduces a second rotor that is used for slab allocations. > > include/linux/cpuset.h | 6 ++++++ > include/linux/sched.h | 1 + > kernel/cpuset.c | 20 ++++++++++++++++---- > mm/slab.c | 2 +- > 4 files changed, 24 insertions(+), 5 deletions(-) Why no update to slob and slub? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>