diff options
author | Ingo Molnar <mingo@elte.hu> | 2008-01-11 13:35:54 +0100 |
---|---|---|
committer | Jens Axboe <jens.axboe@oracle.com> | 2008-01-11 13:35:54 +0100 |
commit | 2997c8c4a0b179e8b834a7f30ba4323f2c60ccf4 (patch) | |
tree | 319fa1c24c380544233890d6ff480a181bf80e96 /block | |
parent | a24eab1ed506f3e0bcbcd3f619558935549d4ace (diff) | |
download | lwn-2997c8c4a0b179e8b834a7f30ba4323f2c60ccf4.tar.gz lwn-2997c8c4a0b179e8b834a7f30ba4323f2c60ccf4.zip |
block: fix blktrace timestamps
David Dillow reported broken blktrace timestamps. The reason
is cpu_clock() which is not a global time source.
Fix bkltrace timestamps by using ktime_get() like the networking
code does for packet timestamps. This also removes a whole lot
of complexity from bkltrace.c and shrinks the code by 500 bytes:
text data bss dec hex filename
2888 124 44 3056 bf0 blktrace.o.before
2390 116 44 2550 9f6 blktrace.o.after
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/blktrace.c | 69 |
1 files changed, 2 insertions, 67 deletions
diff --git a/block/blktrace.c b/block/blktrace.c index 498a0a54a6aa..7471621d4ded 100644 --- a/block/blktrace.c +++ b/block/blktrace.c @@ -25,7 +25,6 @@ #include <linux/time.h> #include <asm/uaccess.h> -static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, }; static unsigned int blktrace_seq __read_mostly = 1; /* @@ -41,7 +40,7 @@ static void trace_note(struct blk_trace *bt, pid_t pid, int action, const int cpu = smp_processor_id(); t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; - t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu); + t->time = ktime_to_ns(ktime_get()); t->device = bt->dev; t->action = action; t->pid = pid; @@ -159,7 +158,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION; t->sequence = ++(*sequence); - t->time = cpu_clock(cpu) - per_cpu(blk_trace_cpu_offset, cpu); + t->time = ktime_to_ns(ktime_get()); t->sector = sector; t->bytes = bytes; t->action = what; @@ -506,73 +505,9 @@ void blk_trace_shutdown(struct request_queue *q) } } -/* - * Average offset over two calls to cpu_clock() with a gettimeofday() - * in the middle - */ -static void blk_check_time(unsigned long long *t, int this_cpu) -{ - unsigned long long a, b; - struct timeval tv; - - a = cpu_clock(this_cpu); - do_gettimeofday(&tv); - b = cpu_clock(this_cpu); - - *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000; - *t -= (a + b) / 2; -} - -/* - * calibrate our inter-CPU timings - */ -static void blk_trace_check_cpu_time(void *data) -{ - unsigned long long *t; - int this_cpu = get_cpu(); - - t = &per_cpu(blk_trace_cpu_offset, this_cpu); - - /* - * Just call it twice, hopefully the second call will be cache hot - * and a little more precise - */ - blk_check_time(t, this_cpu); - blk_check_time(t, this_cpu); - - put_cpu(); -} - -static void blk_trace_set_ht_offsets(void) -{ -#if defined(CONFIG_SCHED_SMT) - int cpu, i; - - /* - * now make sure HT siblings have the same time offset - */ - preempt_disable(); - for_each_online_cpu(cpu) { - unsigned long long *cpu_off, *sibling_off; - - for_each_cpu_mask(i, per_cpu(cpu_sibling_map, cpu)) { - if (i == cpu) - continue; - - cpu_off = &per_cpu(blk_trace_cpu_offset, cpu); - sibling_off = &per_cpu(blk_trace_cpu_offset, i); - *sibling_off = *cpu_off; - } - } - preempt_enable(); -#endif -} - static __init int blk_trace_init(void) { mutex_init(&blk_tree_mutex); - on_each_cpu(blk_trace_check_cpu_time, NULL, 1, 1); - blk_trace_set_ht_offsets(); return 0; } |