lkml.org 
[lkml]   [2013]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFT PATCH v1 7/7] arm64: disable lazy load if FPSIMD registers are frequently used
Date
From: Jiang Liu <jiang.liu@huawei.com>

Disable lazy load if FPSIMD registers are frequently used by the thread,
so we can reduce overhead of lazy FPSIMD restore for FPU extensive
applications. The thresholds are randomly chosen without thorough
benchmarks, we may need to tune it for really systems.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>
---
arch/arm64/include/asm/fpsimd.h | 1 +
arch/arm64/kernel/fpsimd.c | 9 +++++++--
2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 3490935..de6e877 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -37,6 +37,7 @@ struct fpsimd_state {
u32 fpcr;
bool on_hw; /* soft state: whether loaded onto hw */
int last_cpu;
+ int fpu_counter;
};
};
};
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index a81af5f..03e96b8 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -107,7 +107,7 @@ static void fpsimd_load_state_lazy(struct fpsimd_state *state,
__this_cpu_read(fpsimd_owner) == state)
return;

- if (static_key_false(&fpsimd_lazy_mode)) {
+ if (state->fpu_counter < 5 && static_key_false(&fpsimd_lazy_mode)) {
fpsimd_clear_on_hw(state);
fpsimd_enable_trap();
} else if (tsk_used_math(tsk)) {
@@ -124,8 +124,11 @@ static void fpsimd_save_state_lazy(struct fpsimd_state *state)
return;

if (static_key_false(&fpsimd_lazy_mode)) {
- if (!fpsimd_is_on_hw(state))
+ if (!fpsimd_is_on_hw(state)) {
+ state->fpu_counter = clamp(state->fpu_counter - 1,
+ 0, 10);
return;
+ }
}

fpsimd_save_state(state);
@@ -144,6 +147,7 @@ void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
fpsimd_load_state(state);
if (static_key_false(&fpsimd_lazy_mode)) {
fpsimd_set_on_hw(state);
+ state->fpu_counter++;
if (!used_math())
set_used_math();
} else {
@@ -213,6 +217,7 @@ void fpsimd_dup_state(struct fpsimd_state *src, struct fpsimd_state *dst)
preempt_disable();
if (fpsimd_is_on_hw(src))
fpsimd_save_state(dst);
+ dst->fpu_counter = 0;
fpsimd_clear_on_hw(dst);
preempt_enable();
} else if (used_math()) {
--
1.8.1.2


\
 
 \ /
  Last update: 2013-09-27 10:41    [W:0.123 / U:0.660 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site