Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752759AbbHTMPa (ORCPT ); Thu, 20 Aug 2015 08:15:30 -0400 Received: from mail-yk0-f179.google.com ([209.85.160.179]:33210 "EHLO mail-yk0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752723AbbHTMPV (ORCPT ); Thu, 20 Aug 2015 08:15:21 -0400 From: Kevin Hao To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt Subject: [PATCH 8/8] powerpc: use jump label for mmu_has_feature Date: Thu, 20 Aug 2015 20:14:36 +0800 Message-Id: <1440072876-8321-9-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: 3784 Lines: 131 The mmu features are fixed once the probe of mmu features are done. And the function mmu_has_feature() does be used in some hot path. The checking of the mmu features for each time of invoking of mmu_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 (mmu_has_feature(MMU_FTR_XXX)) xxx() Before: lis r9,-16230 lwz r9,12324(r9) lwz r9,24(r9) andi. r10,r9,16 beqlr+ After: nop if MMU_FTR_XXX is enabled b xxx if MMU_FTR_XXX is not enabled Signed-off-by: Kevin Hao --- arch/powerpc/include/asm/mmu.h | 29 +++++++++++++++++++++++++++++ arch/powerpc/kernel/cputable.c | 15 +++++++++++++++ arch/powerpc/kernel/setup_32.c | 1 + arch/powerpc/kernel/setup_64.c | 1 + 4 files changed, 46 insertions(+) diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h index 3d5abfe6ba67..e091de352a75 100644 --- a/arch/powerpc/include/asm/mmu.h +++ b/arch/powerpc/include/asm/mmu.h @@ -109,6 +109,34 @@ DECLARE_PER_CPU(int, next_tlbcam_idx); #endif +#ifdef CONFIG_JUMP_LABEL +#include + +#define MAX_MMU_FEATURES (8 * sizeof(((struct cpu_spec *)0)->mmu_features)) + +extern struct static_key_true mmu_feat_keys[MAX_MMU_FEATURES]; + +extern void mmu_feat_keys_init(void); + +static inline int mmu_has_feature(unsigned long feature) +{ + int i; + + i = __builtin_ctzl(feature); + return static_branch_likely(&mmu_feat_keys[i]); +} + +static inline void mmu_clear_feature(unsigned long feature) +{ + int i; + + i = __builtin_ctzl(feature); + cur_cpu_spec->mmu_features &= ~feature; + static_branch_disable(&mmu_feat_keys[i]); +} +#else +static inline void mmu_feat_keys_init(void) { } + static inline int mmu_has_feature(unsigned long feature) { return (cur_cpu_spec->mmu_features & feature); @@ -118,6 +146,7 @@ static inline void mmu_clear_feature(unsigned long feature) { cur_cpu_spec->mmu_features &= ~feature; } +#endif extern unsigned int __start___mmu_ftr_fixup, __stop___mmu_ftr_fixup; diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c index 7d4fe69a61ed..18a843f139c3 100644 --- a/arch/powerpc/kernel/cputable.c +++ b/arch/powerpc/kernel/cputable.c @@ -2212,4 +2212,19 @@ void __init cpu_feat_keys_init(void) static_branch_disable(&cpu_feat_keys[i]); } } + +DEFINE_STATIC_KEY_TRUE_ARRAY(mmu_feat_keys, MAX_MMU_FEATURES); +EXPORT_SYMBOL_GPL(mmu_feat_keys); + +void __init mmu_feat_keys_init(void) +{ + int i; + + for (i = 0; i < MAX_MMU_FEATURES; i++) { + unsigned long f = 1ul << i; + + if (!(cur_cpu_spec->mmu_features & f)) + static_branch_disable(&mmu_feat_keys[i]); + } +} #endif diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c index 93756175a13c..8acff5a4bc3e 100644 --- a/arch/powerpc/kernel/setup_32.c +++ b/arch/powerpc/kernel/setup_32.c @@ -116,6 +116,7 @@ notrace void __init machine_init(u64 dt_ptr) jump_label_init(); cpu_feat_keys_init(); + mmu_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 4cf3894d91fa..df6f98f1c46c 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -252,6 +252,7 @@ void __init early_setup(unsigned long dt_ptr) jump_label_init(); cpu_feat_keys_init(); + mmu_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/