Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752739AbbHTMPV (ORCPT ); Thu, 20 Aug 2015 08:15:21 -0400 Received: from mail-yk0-f174.google.com ([209.85.160.174]:33151 "EHLO mail-yk0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752683AbbHTMPR (ORCPT ); Thu, 20 Aug 2015 08:15:17 -0400 From: Kevin Hao To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt Subject: [PATCH 7/8] powerpc: use the jump label for cpu_has_feature Date: Thu, 20 Aug 2015 20:14:35 +0800 Message-Id: <1440072876-8321-8-git-send-email-haokexin@gmail.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1440072876-8321-1-git-send-email-haokexin@gmail.com> References: <1440072876-8321-1-git-send-email-haokexin@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4694 Lines: 158 The cpu features are fixed once the probe of cpu features are done. And the function cpu_has_feature() does be used in some hot path. The checking of the cpu features for each time of invoking of cpu_has_feature() seems suboptimal. This tries to reduce this overhead of this check by using jump label. The generated assemble code of the following c program: if (cpu_has_feature(CPU_FTR_XXX)) xxx() Before: lis r9,-16230 lwz r9,12324(r9) lwz r9,12(r9) andi. r10,r9,512 beqlr- After: nop if CPU_FTR_XXX is enabled b xxx if CPU_FTR_XXX is not enabled Signed-off-by: Kevin Hao --- arch/powerpc/include/asm/cpufeatures.h | 20 ++++++++++++++++++++ arch/powerpc/include/asm/cputable.h | 8 ++++++++ arch/powerpc/kernel/cputable.c | 18 ++++++++++++++++++ arch/powerpc/kernel/setup_32.c | 1 + arch/powerpc/kernel/setup_64.c | 1 + 5 files changed, 48 insertions(+) diff --git a/arch/powerpc/include/asm/cpufeatures.h b/arch/powerpc/include/asm/cpufeatures.h index 37650db5044f..405a97fe6ef9 100644 --- a/arch/powerpc/include/asm/cpufeatures.h +++ b/arch/powerpc/include/asm/cpufeatures.h @@ -3,6 +3,25 @@ #include +#ifdef CONFIG_JUMP_LABEL +#include + +extern struct static_key_true cpu_feat_keys[MAX_CPU_FEATURES]; + +static inline int cpu_has_feature(unsigned long feature) +{ + int i; + + if (CPU_FTRS_ALWAYS & feature) + return 1; + + if (!(CPU_FTRS_POSSIBLE & feature)) + return 0; + + i = __builtin_ctzl(feature); + return static_branch_likely(&cpu_feat_keys[i]); +} +#else static inline int cpu_has_feature(unsigned long feature) { return (CPU_FTRS_ALWAYS & feature) || @@ -10,5 +29,6 @@ static inline int cpu_has_feature(unsigned long feature) & cur_cpu_spec->cpu_features & feature); } +#endif #endif /* __ASM_POWERPC_CPUFEATURE_H */ diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h index ae4b6ef341cd..2ebee2894102 100644 --- a/arch/powerpc/include/asm/cputable.h +++ b/arch/powerpc/include/asm/cputable.h @@ -114,6 +114,12 @@ extern void do_feature_fixups(unsigned long value, void *fixup_start, extern const char *powerpc_base_platform; +#ifdef CONFIG_JUMP_LABEL +extern void cpu_feat_keys_init(void); +#else +static inline void cpu_feat_keys_init(void) { } +#endif + /* TLB flush actions. Used as argument to cpu_spec.flush_tlb() hook */ enum { TLB_INVAL_SCOPE_GLOBAL = 0, /* invalidate all TLBs */ @@ -124,6 +130,8 @@ enum { /* CPU kernel features */ +#define MAX_CPU_FEATURES (8 * sizeof(((struct cpu_spec *)0)->cpu_features)) + /* Retain the 32b definitions all use bottom half of word */ #define CPU_FTR_COHERENT_ICACHE ASM_CONST(0x00000001) #define CPU_FTR_L2CR ASM_CONST(0x00000002) diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c index 7d80bfdfb15e..7d4fe69a61ed 100644 --- a/arch/powerpc/kernel/cputable.c +++ b/arch/powerpc/kernel/cputable.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include @@ -2195,3 +2196,20 @@ struct cpu_spec * __init identify_cpu(unsigned long offset, unsigned int pvr) return NULL; } + +#ifdef CONFIG_JUMP_LABEL +DEFINE_STATIC_KEY_TRUE_ARRAY(cpu_feat_keys, MAX_CPU_FEATURES); +EXPORT_SYMBOL_GPL(cpu_feat_keys); + +void __init cpu_feat_keys_init(void) +{ + int i; + + for (i = 0; i < MAX_CPU_FEATURES; i++) { + unsigned long f = 1ul << i; + + if (!(cur_cpu_spec->cpu_features & f)) + static_branch_disable(&cpu_feat_keys[i]); + } +} +#endif diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c index f0868f510b3b..93756175a13c 100644 --- a/arch/powerpc/kernel/setup_32.c +++ b/arch/powerpc/kernel/setup_32.c @@ -115,6 +115,7 @@ notrace void __init machine_init(u64 dt_ptr) lockdep_init(); jump_label_init(); + cpu_feat_keys_init(); /* Enable early debugging if any specified (see udbg.h) */ udbg_early_init(); diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index f0802a0b4a20..4cf3894d91fa 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -251,6 +251,7 @@ void __init early_setup(unsigned long dt_ptr) lockdep_init(); jump_label_init(); + cpu_feat_keys_init(); /* -------- printk is now safe to use ------- */ -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/