We have lots of infrastructure in place to partition a multi-core systems 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. Based on the feedback from this patch set I plan to offer further patches that address similar issue in other code paths. The patch creates an on_each_cpu_mask and on_each_cpu_conf infrastructure API (the former derived from existing arch specific versions in Tile and Arm) and and uses them to turn several global IPI invocation to per CPU group invocations. This 6th iteration includes the following changes: - In case of cpumask allocation failure, have on_each_cpu_cond send an IPI to each needed CPU seperately via smp_call_function_single so no cpumask var is needed, as suggested by Andrew Morton. - Document why on_each_cpu_mask need to check the mask even on UP in a code comment, as suggested by Andrew Morton. - Various typo cleanup in patch descriptions The patch set also available from the ipi_noise_v6 branch at git://github.com/gby/linux.git Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> CC: Christoph Lameter <cl@xxxxxxxxx> CC: Chris Metcalf <cmetcalf@xxxxxxxxxx> CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx> CC: linux-mm@xxxxxxxxx CC: Pekka Enberg <penberg@xxxxxxxxxx> CC: Matt Mackall <mpm@xxxxxxxxxxx> CC: Sasha Levin <levinsasha928@xxxxxxxxx> CC: Rik van Riel <riel@xxxxxxxxxx> CC: Andi Kleen <andi@xxxxxxxxxxxxxx> CC: Mel Gorman <mel@xxxxxxxxx> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> CC: Avi Kivity <avi@xxxxxxxxxx> CC: Michal Nazarewicz <mina86@xxxxxxxxxx> CC: Kosaki Motohiro <kosaki.motohiro@xxxxxxxxx> Gilad Ben-Yossef (8): smp: Introduce a generic on_each_cpu_mask function arm: move arm over to generic on_each_cpu_mask tile: move tile to use generic on_each_cpu_mask smp: add func to IPI cpus based on parameter func slub: only IPI CPUs that have per cpu obj to flush fs: only send IPI to invalidate LRU BH when needed mm: only IPI CPUs to drain local pages if they exist mm: add vmstat counters for tracking PCP drains arch/arm/kernel/smp_tlb.c | 20 +++---------- arch/tile/include/asm/smp.h | 7 ----- arch/tile/kernel/smp.c | 19 ------------- fs/buffer.c | 15 ++++++++++- include/linux/smp.h | 38 ++++++++++++++++++++++++++ include/linux/vm_event_item.h | 1 + kernel/smp.c | 58 +++++++++++++++++++++++++++++++++++++++++ mm/page_alloc.c | 31 +++++++++++++++++++++- mm/slub.c | 10 ++++++- mm/vmstat.c | 2 + 10 files changed, 157 insertions(+), 44 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>