[PATCH v4 0/5] implement vcpu preempted check

Pan Xinhui
2016-10-19T10:20:11Z

change from v3:
add x86 vcpu preempted check patch
change from v2:
no code change, fix typos, update some comments
change from v1:
a simplier definition of default vcpu_is_preempted
skip mahcine type check on ppc, and add config. remove dedicated macro.
add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner.
add more comments
thanks boqun and Peter's suggestion.

This patch set aims to fix lock holder preemption issues.

test-case:
perf record -a perf bench sched messaging -g 400 -p && perf report

18.09% sched-messaging [kernel.vmlinux] [k] osq_lock
12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner
5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock
3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task
3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq
3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is
2.49% sched-messaging [kernel.vmlinux] [k] system_call

We introduce interface bool vcpu_is_preempted(int cpu) and use it in some spin
loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner.
These spin_on_onwer variant also cause rcu stall before we apply this patch set

We also have observed some performace improvements.

PPC test result:

1 copy - 0.94%
2 copy - 7.17%
4 copy - 11.9%
8 copy - 3.04%
16 copy - 15.11%

details below:
Without patch:

1 copy - File Write 4096 bufsize 8000 maxblocks 2188223.0 KBps (30.0 s, 1 samples)
2 copy - File Write 4096 bufsize 8000 maxblocks 1804433.0 KBps (30.0 s, 1 samples)
4 copy - File Write 4096 bufsize 8000 maxblocks 1237257.0 KBps (30.0 s, 1 samples)
8 copy - File Write 4096 bufsize 8000 maxblocks 1032658.0 KBps (30.0 s, 1 samples)
16 copy - File Write 4096 bufsize 8000 maxblocks 768000.0 KBps (30.1 s, 1 samples)

With patch:

1 copy - File Write 4096 bufsize 8000 maxblocks 2209189.0 KBps (30.0 s, 1 samples)
2 copy - File Write 4096 bufsize 8000 maxblocks 1943816.0 KBps (30.0 s, 1 samples)
4 copy - File Write 4096 bufsize 8000 maxblocks 1405591.0 KBps (30.0 s, 1 samples)
8 copy - File Write 4096 bufsize 8000 maxblocks 1065080.0 KBps (30.0 s, 1 samples)
16 copy - File Write 4096 bufsize 8000 maxblocks 904762.0 KBps (30.0 s, 1 samples)

X86 test result:
test-case after-patch before-patch
Execl Throughput | 18307.9 lps | 11701.6 lps
File Copy 1024 bufsize 2000 maxblocks | 1352407.3 KBps | 790418.9 KBps
File Copy 256 bufsize 500 maxblocks | 367555.6 KBps | 222867.7 KBps
File Copy 4096 bufsize 8000 maxblocks | 3675649.7 KBps | 1780614.4 KBps
Pipe Throughput | 11872208.7 lps | 11855628.9 lps
Pipe-based Context Switching | 1495126.5 lps | 1490533.9 lps
Process Creation | 29881.2 lps | 28572.8 lps
Shell Scripts (1 concurrent) | 23224.3 lpm | 22607.4 lpm
Shell Scripts (8 concurrent) | 3531.4 lpm | 3211.9 lpm
System Call Overhead | 10385653.0 lps | 10419979.0 lps

Pan Xinhui (5):
kernel/sched: introduce vcpu preempted check interface
locking/osq: Drop the overload of osq_lock()
kernel/locking: Drop the overload of {mutex,rwsem}_spin_on_owner
powerpc/spinlock: support vcpu preempted check
x86, kvm: support vcpu preempted check

arch/powerpc/include/asm/spinlock.h | 8 ++++++++
arch/x86/include/asm/paravirt_types.h | 6 ++++++
arch/x86/include/asm/spinlock.h | 8 ++++++++
arch/x86/include/uapi/asm/kvm_para.h | 3 ++-
arch/x86/kernel/kvm.c | 11 +++++++++++
arch/x86/kernel/paravirt.c | 11 +++++++++++
arch/x86/kvm/x86.c | 12 ++++++++++++
include/linux/sched.h | 12 ++++++++++++
kernel/locking/mutex.c | 15 +++++++++++++--
kernel/locking/osq_lock.c | 10 +++++++++-
kernel/locking/rwsem-xadd.c | 16 +++++++++++++---
11 files changed, 105 insertions(+), 7 deletions(-)

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2.4.11