Messages in this thread Patch in this message | | | From | Ido Yariv <> | Subject | [PATCH v2 2/2] x86/pat: Avoid contention on cpa_lock if possible | Date | Wed, 8 Aug 2012 20:01:39 +0300 |
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vSMP Foundation does not require to serialize CPA by guaranteeing that the most recent TLB entry will always be used.
To avoid needless contention on cpa_lock, do not lock/unlock it if it isn't necessary.
Based on work by Shai Fultheim <shai@scalemp.com>.
Signed-off-by: Ido Yariv <ido@wizery.com> Acked-by: Shai Fultheim <shai@scalemp.com> --- Changes from v1: - Use a synthetic CPUID bit and a use static_cpu_has() as suggested by H. Peter Avnin
arch/x86/include/asm/cpufeature.h | 1 + arch/x86/kernel/vsmp_64.c | 10 ++++++++++ arch/x86/mm/pageattr.c | 30 +++++++++++++++++++++--------- 3 files changed, 32 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 6b7ee5f..92303a0 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -97,6 +97,7 @@ #define X86_FEATURE_EXTD_APICID (3*32+26) /* has extended APICID (8 bits) */ #define X86_FEATURE_AMD_DCM (3*32+27) /* multi-node processor */ #define X86_FEATURE_APERFMPERF (3*32+28) /* APERFMPERF */ +#define X86_FEATURE_NO_CPA_LOCK (3*32+29) /* Serializing cpa is not required */ /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ #define X86_FEATURE_XMM3 (4*32+ 0) /* "pni" SSE-3 */ diff --git a/arch/x86/kernel/vsmp_64.c b/arch/x86/kernel/vsmp_64.c index f655f2c..994359b 100644 --- a/arch/x86/kernel/vsmp_64.c +++ b/arch/x86/kernel/vsmp_64.c @@ -235,9 +235,19 @@ static void __init vsmp_platform_setup(void) set_vsmp_pv_ops(); } +static void __cpuinit vsmp_set_cpu_features(struct cpuinfo_x86 *c) +{ + /* + * vSMP guarantees that the most recent TLB entry will always be used, + * so we can avoid serializing cpa + */ + set_cpu_cap(c, X86_FEATURE_NO_CPA_LOCK); +} + const __refconst struct hypervisor_x86 x86_hyper_vsmp = { .name = "ScaleMP vSMP Foundation", .detect = detect_vsmp_box, .init_platform = vsmp_platform_setup, + .set_cpu_features = vsmp_set_cpu_features, }; EXPORT_SYMBOL(x86_hyper_vsmp); diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 931930a..95fbb41 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -46,7 +46,7 @@ struct cpa_data { * entries change the page attribute in parallel to some other cpu * splitting a large page entry along with changing the attribute. */ -static DEFINE_SPINLOCK(cpa_lock); +static DEFINE_SPINLOCK(_cpa_lock); #define CPA_FLUSHTLB 1 #define CPA_ARRAY 2 @@ -110,6 +110,22 @@ static inline unsigned long highmap_end_pfn(void) # define debug_pagealloc 0 #endif +static inline void cpa_lock(void) +{ + if (debug_pagealloc || static_cpu_has(X86_FEATURE_NO_CPA_LOCK)) + return; + + spin_lock(&_cpa_lock); +} + +static inline void cpa_unlock(void) +{ + if (debug_pagealloc || static_cpu_has(X86_FEATURE_NO_CPA_LOCK)) + return; + + spin_unlock(&_cpa_lock); +} + static inline int within(unsigned long addr, unsigned long start, unsigned long end) { @@ -509,11 +525,9 @@ static int split_large_page(pte_t *kpte, unsigned long address) pgprot_t ref_prot; struct page *base; - if (!debug_pagealloc) - spin_unlock(&cpa_lock); + cpa_unlock(); base = alloc_pages(GFP_KERNEL | __GFP_NOTRACK, 0); - if (!debug_pagealloc) - spin_lock(&cpa_lock); + cpa_lock(); if (!base) return -ENOMEM; @@ -801,11 +815,9 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias) if (cpa->flags & (CPA_ARRAY | CPA_PAGES_ARRAY)) cpa->numpages = 1; - if (!debug_pagealloc) - spin_lock(&cpa_lock); + cpa_lock(); ret = __change_page_attr(cpa, checkalias); - if (!debug_pagealloc) - spin_unlock(&cpa_lock); + cpa_unlock(); if (ret) return ret; -- 1.7.7.6
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