Mel Gorman <mgorman@xxxxxxx> writes: > On Wed, Dec 02, 2020 at 04:42:33PM +0800, Huang Ying wrote: >> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> >> --- >> man2/set_mempolicy.2 | 9 +++++++++ >> 1 file changed, 9 insertions(+) >> >> diff --git a/man2/set_mempolicy.2 b/man2/set_mempolicy.2 >> index 68011eecb..3754b3e12 100644 >> --- a/man2/set_mempolicy.2 >> +++ b/man2/set_mempolicy.2 >> @@ -113,6 +113,12 @@ A nonempty >> .I nodemask >> specifies node IDs that are relative to the set of >> node IDs allowed by the process's current cpuset. >> +.TP >> +.BR MPOL_F_NUMA_BALANCING " (since Linux 5.11)" >> +Enable the Linux kernel NUMA balancing for the task if it is supported >> +by kernel. >> +If the flag isn't supported by Linux kernel, return -1 and errno is >> +set to EINVAL. >> .PP >> .I nodemask >> points to a bit mask of node IDs that contains up to >> @@ -293,6 +299,9 @@ argument specified both > > Should this be expanded more to clarify it applies to MPOL_BIND > specifically? > > Maybe the first patch should be expanded more and explictly fail if > MPOL_F_NUMA_BALANCING is used with anything other than MPOL_BIND? For MPOL_PREFERRED, why could we not use NUMA balancing to migrate pages to the accessing local node if it is same as the preferred node? We have a way to turn off NUMA balancing already, why could we not provide a way to enable it if that's intended? Even for MPOL_INTERLEAVE, if the target node is the same as the accessing local node, can we use NUMA balancing to migrate pages? So, I prefer to make MPOL_F_NUMA_BALANCING to be Optimizing with NUMA balancing if possible, and we may add more optimization in the future. Do you agree? Best Regards, Huang, Ying >> .B MPOL_F_STATIC_NODES >> and >> .BR MPOL_F_RELATIVE_NODES . >> +Or, the >> +.B MPOL_F_NUMA_BALANCING >> +isn't supported by the Linux kernel. > > This will be difficult for an app to distinguish but we can't go back in > time and make this ENOSYS :( > > The linux-api people might have more guidance but it may go to the > extent of including a small test program in the manual page for a > sequence that tests whether MPOL_F_NUMA_BALANCING works. They might have > a better recommendation on how it should be handled.
