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| author | Shaohua Li <shaohua.li@intel.com> | 2011-01-17 10:52:07 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-02-14 13:03:08 +0100 |
| commit | 70e4a369733a21e3d16b059a6ccdad22a344bf57 (patch) | |
| tree | bb103a7ea3199320dc0b7e5fdf69fe594b863e05 | |
| parent | 3a09fb4570a1cce11472b8e5da3f6ee409f529d5 (diff) | |
| download | lwn-70e4a369733a21e3d16b059a6ccdad22a344bf57.tar.gz lwn-70e4a369733a21e3d16b059a6ccdad22a344bf57.zip | |
x86: Scale up the number of TLB invalidate vectors with NR_CPUs, up to 32
Make the maxium TLB invalidate vectors depend on NR_CPUS linearly,
with a maximum of 32 vectors.
We currently only have 8 vectors for TLB invalidation and that is clearly
inadequate. If we have a lot of CPUs, the CPUs need share the 8 vectors and
tlbstate_lock is used to protect them. flush_tlb_page() is
heavily used in page reclaim, which will cause a lot of lock
contention for tlbstate_lock.
Andi Kleen suggested increasing the vectors number to 32, which should be
good for current typical systems to reduce the tlbstate_lock contention.
My test system has 4 sockets and 64G memory, and 64 CPUs. My
workload creates 64 processes. Each process mmap reads a big
empty sparse file. The total size of the files are 2*total_mem,
so this will cause a lot of page reclaim.
Below is the result I get from perf call-graph profiling:
without the patch:
------------------
24.25% usemem [kernel] [k] _raw_spin_lock
|
--- _raw_spin_lock
|
|--42.15%-- native_flush_tlb_others
with the patch:
------------------
14.96% usemem [kernel] [k] _raw_spin_lock
|
--- _raw_spin_lock
|--13.89%-- native_flush_tlb_others
So this heavily reduces the tlbstate_lock contention.
Suggested-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1295232727.1949.709.camel@sli10-conroe>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/include/asm/irq_vectors.h | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h index 42f0d4a30f1b..4980f48bbbb7 100644 --- a/arch/x86/include/asm/irq_vectors.h +++ b/arch/x86/include/asm/irq_vectors.h @@ -17,8 +17,8 @@ * Vectors 0 ... 31 : system traps and exceptions - hardcoded events * Vectors 32 ... 127 : device interrupts * Vector 128 : legacy int80 syscall interface - * Vectors 129 ... 229 : device interrupts - * Vectors 230 ... 255 : special interrupts + * Vectors 129 ... INVALIDATE_TLB_VECTOR_START-1 : device interrupts + * Vectors INVALIDATE_TLB_VECTOR_START ... 255 : special interrupts * * 64-bit x86 has per CPU IDT tables, 32-bit has one shared IDT table. * @@ -124,8 +124,13 @@ */ #define LOCAL_TIMER_VECTOR 0xef -/* f0-f7 used for spreading out TLB flushes: */ -#define NUM_INVALIDATE_TLB_VECTORS 8 +/* up to 32 vectors used for spreading out TLB flushes: */ +#if NR_CPUS <= 32 +# define NUM_INVALIDATE_TLB_VECTORS NR_CPUS +#else +# define NUM_INVALIDATE_TLB_VECTORS 32 +#endif + #define INVALIDATE_TLB_VECTOR_END 0xee #define INVALIDATE_TLB_VECTOR_START \ (INVALIDATE_TLB_VECTOR_END - NUM_INVALIDATE_TLB_VECTORS + 1) |