From: Yang Zhang <yang.zhang...@gmail.com> Some latency-intensive workload will see obviously performance drop when running inside VM. The main reason is that the overhead is amplified when running inside VM. The most cost i have seen is inside idle path. This patch introduces a new mechanism to poll for a while before entering idle state. If schedule is needed during poll, then we don't need to goes through the heavy overhead path.
Here is the data i get when running benchmark contextswitch (https://github.com/tsuna/contextswitch) before patch: 2000000 process context switches in 4822613801ns (2411.3ns/ctxsw) after patch: 2000000 process context switches in 3584098241ns (1792.0ns/ctxsw) Yang Zhang (2): x86/idle: add halt poll for halt idle x86/idle: use dynamic halt poll Documentation/sysctl/kernel.txt | 24 ++++++++++ arch/x86/include/asm/processor.h | 6 +++ arch/x86/kernel/apic/apic.c | 6 +++ arch/x86/kernel/apic/vector.c | 1 + arch/x86/kernel/cpu/mcheck/mce_amd.c | 2 + arch/x86/kernel/cpu/mcheck/therm_throt.c | 2 + arch/x86/kernel/cpu/mcheck/threshold.c | 2 + arch/x86/kernel/irq.c | 5 ++ arch/x86/kernel/irq_work.c | 2 + arch/x86/kernel/process.c | 80 ++++++++++++++++++++++++++++++++ arch/x86/kernel/smp.c | 6 +++ include/linux/kernel.h | 5 ++ kernel/sched/idle.c | 3 ++ kernel/sysctl.c | 23 +++++++++ 14 files changed, 167 insertions(+) -- 1.8.3.1
