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authorStuart Menefy <stuart.menefy@st.com>2009-09-25 18:25:10 +0100
committerPaul Mundt <lethal@linux-sh.org>2009-11-24 17:45:38 +0900
commitd3ea9fa0a563620fe9f416f94bb8927c64390917 (patch)
tree0aa1278ac7929f936fc4fd8daf235930f6164d18 /arch/sh/math-emu
parent39ac11c1607f1d566e7cf885acd403fa4f07f8a2 (diff)
downloadvexpress-lsk-d3ea9fa0a563620fe9f416f94bb8927c64390917.tar.gz
sh: Minor optimisations to FPU handling
A number of small optimisations to FPU handling, in particular: - move the task USEDFPU flag from the thread_info flags field (which is accessed asynchronously to the thread) to a new status field, which is only accessed by the thread itself. This allows locking to be removed in most cases, or can be reduced to a preempt_lock(). This mimics the i386 behaviour. - move the modification of regs->sr and thread_info->status flags out of save_fpu() to __unlazy_fpu(). This gives the compiler a better chance to optimise things, as well as making save_fpu() symmetrical with restore_fpu() and init_fpu(). - implement prepare_to_copy(), so that when creating a thread, we can unlazy the FPU prior to copying the thread data structures. Also make sure that the FPU is disabled while in the kernel, in particular while booting, and for newly created kernel threads, In a very artificial benchmark, the execution time for 2500000 context switches was reduced from 50 to 45 seconds. Signed-off-by: Stuart Menefy <stuart.menefy@st.com> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'arch/sh/math-emu')
-rw-r--r--arch/sh/math-emu/math.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/sh/math-emu/math.c b/arch/sh/math-emu/math.c
index ac2d7abd256..d6c15cae091 100644
--- a/arch/sh/math-emu/math.c
+++ b/arch/sh/math-emu/math.c
@@ -558,7 +558,7 @@ static int ieee_fpe_handler(struct pt_regs *regs)
(finsn >> 8) & 0xf);
tsk->thread.fpu.hard.fpscr &=
~(FPSCR_CAUSE_MASK | FPSCR_FLAG_MASK);
- set_tsk_thread_flag(tsk, TIF_USEDFPU);
+ task_thread_info(tsk)->status |= TS_USEDFPU;
} else {
info.si_signo = SIGFPE;
info.si_errno = 0;
@@ -619,10 +619,10 @@ int do_fpu_inst(unsigned short inst, struct pt_regs *regs)
struct task_struct *tsk = current;
struct sh_fpu_soft_struct *fpu = &(tsk->thread.fpu.soft);
- if (!test_tsk_thread_flag(tsk, TIF_USEDFPU)) {
+ if (!(task_thread_info(tsk)->status & TS_USEDFPU)) {
/* initialize once. */
fpu_init(fpu);
- set_tsk_thread_flag(tsk, TIF_USEDFPU);
+ task_thread_info(tsk)->status |= TS_USEDFPU;
}
return fpu_emulate(inst, fpu, regs);