diff options
| author | Stuart Menefy <stuart.menefy@st.com> | 2009-09-25 18:25:10 +0100 |
|---|---|---|
| committer | Paul Mundt <lethal@linux-sh.org> | 2009-11-24 17:45:38 +0900 |
| commit | d3ea9fa0a563620fe9f416f94bb8927c64390917 (patch) | |
| tree | 0aa1278ac7929f936fc4fd8daf235930f6164d18 /arch/sh/include/asm/thread_info.h | |
| parent | 39ac11c1607f1d566e7cf885acd403fa4f07f8a2 (diff) | |
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/include/asm/thread_info.h')
| -rw-r--r-- | arch/sh/include/asm/thread_info.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/sh/include/asm/thread_info.h b/arch/sh/include/asm/thread_info.h index 23eeed89467..1f3d927e226 100644 --- a/arch/sh/include/asm/thread_info.h +++ b/arch/sh/include/asm/thread_info.h @@ -51,6 +51,7 @@ struct thread_info { .task = &tsk, \ .exec_domain = &default_exec_domain, \ .flags = 0, \ + .status = 0, \ .cpu = 0, \ .preempt_count = INIT_PREEMPT_COUNT, \ .addr_limit = KERNEL_DS, \ @@ -117,7 +118,6 @@ extern void free_thread_info(struct thread_info *ti); #define TIF_SECCOMP 6 /* secure computing */ #define TIF_NOTIFY_RESUME 7 /* callback before returning to user */ #define TIF_SYSCALL_TRACEPOINT 8 /* for ftrace syscall instrumentation */ -#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */ #define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */ #define TIF_MEMDIE 18 #define TIF_FREEZE 19 /* Freezing for suspend */ @@ -130,7 +130,6 @@ extern void free_thread_info(struct thread_info *ti); #define _TIF_SECCOMP (1 << TIF_SECCOMP) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT) -#define _TIF_USEDFPU (1 << TIF_USEDFPU) #define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG) #define _TIF_FREEZE (1 << TIF_FREEZE) @@ -163,6 +162,7 @@ extern void free_thread_info(struct thread_info *ti); * have to worry about atomic accesses. */ #define TS_RESTORE_SIGMASK 0x0001 /* restore signal mask in do_signal() */ +#define TS_USEDFPU 0x0002 /* FPU used by this task this quantum */ #ifndef __ASSEMBLY__ #define HAVE_SET_RESTORE_SIGMASK 1 |