Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753377Ab3I0ILh (ORCPT ); Fri, 27 Sep 2013 04:11:37 -0400 Received: from mail-pd0-f175.google.com ([209.85.192.175]:43322 "EHLO mail-pd0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751526Ab3I0ILa (ORCPT ); Fri, 27 Sep 2013 04:11:30 -0400 From: Jiang Liu To: Catalin Marinas , Will Deacon , Jiang Liu , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Jiang Liu Subject: [RFT PATCH v1 6/7] amd64: avoid saving and restoring FPSIMD registers until threads access them Date: Fri, 27 Sep 2013 16:04:46 +0800 Message-Id: <1380269087-8520-7-git-send-email-liuj97@gmail.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1380269087-8520-1-git-send-email-liuj97@gmail.com> References: <1380269087-8520-1-git-send-email-liuj97@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4346 Lines: 147 From: Jiang Liu Use PF_USED_MATH flag to mark whether the thread has accessed any FPSIMD registers, so we could avoid saving and restroing FPSIMD registers until threads access them. This may improve performance when lazy FPSIMD restore is disabled. Signed-off-by: Jiang Liu Cc: Jiang Liu --- arch/arm64/kernel/fpsimd.c | 38 +++++++++++++++++++++++--------------- 1 file changed, 23 insertions(+), 15 deletions(-) diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 267e54a..a81af5f 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -99,7 +99,8 @@ void fpsimd_disable_lazy_restore(void) * If lazy mode is enabled, caller needs to disable preemption * when calling fpsimd_load_state_lazy() and fpsimd_save_state_lazy(). */ -static void fpsimd_load_state_lazy(struct fpsimd_state *state) +static void fpsimd_load_state_lazy(struct fpsimd_state *state, + struct task_struct *tsk) { /* Could we reuse the hardware context? */ if (state->last_cpu == smp_processor_id() && @@ -109,13 +110,19 @@ static void fpsimd_load_state_lazy(struct fpsimd_state *state) if (static_key_false(&fpsimd_lazy_mode)) { fpsimd_clear_on_hw(state); fpsimd_enable_trap(); - } else { + } else if (tsk_used_math(tsk)) { + fpsimd_disable_trap(); fpsimd_load_state(state); + } else { + fpsimd_enable_trap(); } } static void fpsimd_save_state_lazy(struct fpsimd_state *state) { + if (!used_math()) + return; + if (static_key_false(&fpsimd_lazy_mode)) { if (!fpsimd_is_on_hw(state)) return; @@ -133,12 +140,14 @@ void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs) { struct fpsimd_state *state = ¤t->thread.fpsimd_state; + fpsimd_disable_trap(); + fpsimd_load_state(state); if (static_key_false(&fpsimd_lazy_mode)) { - fpsimd_disable_trap(); - fpsimd_load_state(state); fpsimd_set_on_hw(state); + if (!used_math()) + set_used_math(); } else { - WARN_ON(1); + set_used_math(); } } @@ -175,7 +184,7 @@ void fpsimd_thread_switch(struct task_struct *next) if (current->mm) fpsimd_save_state_lazy(¤t->thread.fpsimd_state); if (next->mm) - fpsimd_load_state_lazy(&next->thread.fpsimd_state); + fpsimd_load_state_lazy(&next->thread.fpsimd_state, next); } void fpsimd_flush_thread(void) @@ -187,8 +196,9 @@ void fpsimd_flush_thread(void) #if (AARCH64_FPCR_DEFAULT_VAL != 0) state->fpcr = AARCH64_FPCR_DEFAULT_VAL; #endif + clear_used_math(); fpsimd_set_last_cpu(state, -1); - fpsimd_load_state_lazy(state); + fpsimd_load_state_lazy(state, current); preempt_enable(); } @@ -205,7 +215,7 @@ void fpsimd_dup_state(struct fpsimd_state *src, struct fpsimd_state *dst) fpsimd_save_state(dst); fpsimd_clear_on_hw(dst); preempt_enable(); - } else { + } else if (used_math()) { fpsimd_save_state(dst); } fpsimd_set_last_cpu(dst, -1); @@ -226,12 +236,12 @@ void fpsimd_prepare_sigctx(struct fpsimd_state *ctx) preempt_disable(); if (fpsimd_is_on_hw(ctx)) { fpsimd_init_hw_state(); - } else { + } else if (used_math()) { ctx->fpsr = 0; ctx->fpcr = AARCH64_FPCR_DEFAULT_VAL; } preempt_enable(); - } else { + } else if (used_math()) { fpsimd_init_hw_state(); } } @@ -243,7 +253,7 @@ void fpsimd_restore_sigctx(struct fpsimd_state *ctx) preempt_disable(); *state = *ctx; __this_cpu_write(fpsimd_owner, NULL); - fpsimd_load_state_lazy(state); + fpsimd_load_state_lazy(state, current); preempt_enable(); } @@ -261,9 +271,7 @@ void kernel_neon_begin(void) if (current->mm) fpsimd_save_state_lazy(¤t->thread.fpsimd_state); - if (static_key_false(&fpsimd_lazy_mode)) - fpsimd_disable_trap(); - + fpsimd_disable_trap(); fpsimd_init_hw_state(); __this_cpu_write(fpsimd_owner, NULL); } @@ -272,7 +280,7 @@ EXPORT_SYMBOL(kernel_neon_begin); void kernel_neon_end(void) { if (current->mm) - fpsimd_load_state_lazy(¤t->thread.fpsimd_state); + fpsimd_load_state_lazy(¤t->thread.fpsimd_state, current); preempt_enable(); } -- 1.8.1.2 -- 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/