We have lots of infrastructure in place to partition a multi-core system such that we have a group of CPUs that are dedicated to specific task: cgroups, scheduler and interrupt affinity and cpuisol boot parameter. Still, kernel code will some time interrupt all CPUs in the system via IPIs for various needs. These IPIs are useful and cannot be avoided altogether, but in certain cases it is possible to interrupt only specific CPUs that have useful work to do and not the entire system. This patch set, inspired by discussions with Peter Zijlstra and Frederic Weisbecker when testing the nohz task patch set, is a first stab at trying to explore doing this by locating the places where such global IPI calls are being made and turning a global IPI into an IPI for a specific group of CPUs. The purpose of the patch set is to get feedback if this is the right way to go for dealing with this issue and indeed, if the issue is even worth dealing with at all. This first version creates an on_each_cpu_mask infrastructure API (derived from existing arch specific versions in Tile and Arm) and uses it to turn two global IPI invocation to per CPU group invocations. The patch is against 3.1-rc4 and was compiled for x86 and arm in both UP and SMP mode (I could not get Tile to build, regardless of this patch) and was further tested by running hackbench on x86 in SMP mode in a 4 CPUs VM. No obvious regression where noted, but I obviously did not test this quite enough. Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx> CC: Russell King <linux@xxxxxxxxxxxxxxxx> CC: Chris Metcalf <cmetcalf@xxxxxxxxxx> CC: linux-mm@xxxxxxxxx CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> CC: Pekka Enberg <penberg@xxxxxxxxxx> CC: Matt Mackall <mpm@xxxxxxxxxxx> Ben-Yossef (5): Introduce a generic on_each_cpu_mask function Move arm over to generic on_each_cpu_mask Move tile to use generic on_each_cpu_mask Only IPI CPUs to drain local pages if they exist slub: only IPI CPUs that have per cpu obj to flush arch/arm/kernel/smp_tlb.c | 20 ++++------------ arch/tile/include/asm/smp.h | 7 ----- arch/tile/kernel/smp.c | 19 --------------- include/linux/smp.h | 14 +++++++++++ kernel/smp.c | 20 ++++++++++++++++ mm/page_alloc.c | 53 +++++++++++++++++++++++++++++++++++------- mm/slub.c | 15 +++++++++++- 7 files changed, 97 insertions(+), 51 deletions(-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>