Re: Linus rollup
From: Andrew Morton <hidden>
Date: 2003-01-30 01:10:50
"David S. Miller" [off-list ref] wrote:
From: Andrew Morton [off-list ref] Date: Wed, 29 Jan 2003 15:12:06 -0800 But that would be a separate patch. _all_ we are doing here is fixing and optimising the xtime_lock problems. We should seek to do that with "equivalent transformations". I agree, do this and arch people can tweak later.
Stephen has already tweaked. Hopefully Andi and David can review this sometime: This is an optimisation to the ia64, ia32 and x86_64 do_gettimeofday() code above and beyond the base frlock work. Patch from Stephen Hemminger [off-list ref] * Don't need to disable interrupts on ia64, x86_64 or ia32 with TSC getttimeofday. Disabling interrupts is noticeably slower ~3% so would really like to only do it if necessary. * Some more cleanup of frlock.h in the macro's that aren't being used yet. arch/i386/kernel/time.c | 7 +++---- arch/i386/kernel/timers/timer_pit.c | 7 +++---- arch/ia64/kernel/time.c | 5 ++--- include/linux/frlock.h | 8 ++++++-- i386/kernel/apm.c | 0 5 files changed, 14 insertions(+), 13 deletions(-) diff -puN arch/i386/kernel/apm.c~do_gettimeofday-speedup arch/i386/kernel/apm.c diff -puN arch/i386/kernel/time.c~do_gettimeofday-speedup arch/i386/kernel/time.c
--- 25/arch/i386/kernel/time.c~do_gettimeofday-speedup Wed Jan 29 16:39:41 2003
+++ 25-akpm/arch/i386/kernel/time.c Wed Jan 29 16:39:41 2003@@ -86,22 +86,21 @@ struct timer_opts* timer = &timer_none; */ void do_gettimeofday(struct timeval *tv) { - unsigned long flags; unsigned long seq; unsigned long usec, sec; do { - seq = fr_read_begin_irqsave(&xtime_lock, flags); + seq = fr_read_begin(&xtime_lock); usec = timer->get_offset(); { unsigned long lost = jiffies - wall_jiffies; - if (lost) + if (unlikely(lost != 0)) usec += lost * (1000000 / HZ); } sec = xtime.tv_sec; usec += (xtime.tv_nsec / 1000); - } while (unlikely(seq != fr_read_end_irqrestore(&xtime_lock, flags))); + } while (unlikely(seq != fr_read_end(&xtime_lock))); while (usec >= 1000000) { usec -= 1000000;
diff -puN arch/i386/kernel/timers/timer_pit.c~do_gettimeofday-speedup arch/i386/kernel/timers/timer_pit.c
--- 25/arch/i386/kernel/timers/timer_pit.c~do_gettimeofday-speedup Wed Jan 29 16:39:41 2003
+++ 25-akpm/arch/i386/kernel/timers/timer_pit.c Wed Jan 29 16:39:41 2003@@ -76,7 +76,7 @@ static void delay_pit(unsigned long loop static unsigned long get_offset_pit(void) { int count; - + unsigned long flags; static int count_p = LATCH; /* for the first call after boot */ static unsigned long jiffies_p = 0;
@@ -85,8 +85,7 @@ static unsigned long get_offset_pit(void */ unsigned long jiffies_t; - /* gets recalled with irq locally disabled */ - spin_lock(&i8253_lock); + spin_lock_irqsave(&i8253_lock, flags); /* timer count may underflow right here */ outb_p(0x00, 0x43); /* latch the count ASAP */
@@ -108,7 +107,7 @@ static unsigned long get_offset_pit(void count = LATCH - 1; } - spin_unlock(&i8253_lock); + spin_unlock_irqrestore(&i8253_lock, flags); /* * avoiding timer inconsistencies (they are rare, but they happen)...
diff -puN arch/ia64/kernel/time.c~do_gettimeofday-speedup arch/ia64/kernel/time.c
--- 25/arch/ia64/kernel/time.c~do_gettimeofday-speedup Wed Jan 29 16:39:41 2003
+++ 25-akpm/arch/ia64/kernel/time.c Wed Jan 29 16:39:41 2003@@ -117,11 +117,10 @@ do_settimeofday (struct timeval *tv) void do_gettimeofday (struct timeval *tv) { - unsigned long flags; unsigned long seq, usec, sec, old; do { - seq = fr_read_begin_irqsave(&xtime_lock, flags); + seq = fr_read_begin(&xtime_lock); usec = gettimeoffset(); /*
@@ -138,7 +137,7 @@ do_gettimeofday (struct timeval *tv) sec = xtime.tv_sec; usec += xtime.tv_nsec / 1000; - } while (seq != fr_read_end_irqrestore(&xtime_lock, flags)); + } while (seq != fr_read_end(&xtime_lock)); while (usec >= 1000000) {
diff -puN include/linux/frlock.h~do_gettimeofday-speedup include/linux/frlock.h
--- 25/include/linux/frlock.h~do_gettimeofday-speedup Wed Jan 29 16:39:41 2003
+++ 25-akpm/include/linux/frlock.h Wed Jan 29 16:42:15 2003@@ -64,6 +64,9 @@ static inline void fr_write_end(frlock_t preempt_enable(); } +/* Lock out other writers and update the count. + * Acts like a normal spin_lock/unlock. + */ static inline void fr_write_lock(frlock_t *rw) { spin_lock(&rw->lock);
@@ -82,11 +85,12 @@ static inline int fr_write_trylock(frloc if (ret) { ++rw->pre_sequence; - wmb(); + mb(); } return ret; } +/* Start of read calculation -- fetch last complete writer token */ static inline unsigned fr_read_begin(const frlock_t *rw) { unsigned ret = rw->post_sequence;
@@ -95,6 +99,7 @@ static inline unsigned fr_read_begin(con } +/* End of reader calculation -- fetch last writer start token */ static inline unsigned fr_read_end(const frlock_t *rw) { rmb();
@@ -128,4 +133,3 @@ static inline unsigned fr_read_end(const }) #endif /* __LINUX_FRLOCK_H */ -
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