diff options
author | Ingo Molnar <mingo@elte.hu> | 2008-07-30 04:22:07 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-07-31 11:21:01 -0400 |
commit | 4a273f209cc95d148f79b4c96d3d03997b44ffda (patch) | |
tree | 0d3d0aec4e676baacc2afd2e731b8905257a0b32 | |
parent | 56b906126d33904d4d67615d0d5b95dbdf1f27ca (diff) |
sched clock: couple local and remote clocks
When taking the time of a remote CPU, use the opportunity to
couple (sync) the clocks to each other. (in a monotonic way)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Mike Galbraith <efault@gmx.de>
-rw-r--r-- | kernel/sched_clock.c | 33 |
1 files changed, 21 insertions, 12 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index 857a1291fd23..074edc989379 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c | |||
@@ -149,7 +149,7 @@ static void lock_double_clock(struct sched_clock_data *data1, | |||
149 | u64 sched_clock_cpu(int cpu) | 149 | u64 sched_clock_cpu(int cpu) |
150 | { | 150 | { |
151 | struct sched_clock_data *scd = cpu_sdc(cpu); | 151 | struct sched_clock_data *scd = cpu_sdc(cpu); |
152 | u64 now, clock; | 152 | u64 now, clock, this_clock, remote_clock; |
153 | 153 | ||
154 | if (unlikely(!sched_clock_running)) | 154 | if (unlikely(!sched_clock_running)) |
155 | return 0ull; | 155 | return 0ull; |
@@ -158,26 +158,36 @@ u64 sched_clock_cpu(int cpu) | |||
158 | now = sched_clock(); | 158 | now = sched_clock(); |
159 | 159 | ||
160 | if (cpu != raw_smp_processor_id()) { | 160 | if (cpu != raw_smp_processor_id()) { |
161 | /* | ||
162 | * in order to update a remote cpu's clock based on our | ||
163 | * unstable raw time rebase it against: | ||
164 | * tick_raw (offset between raw counters) | ||
165 | * tick_gotd (tick offset between cpus) | ||
166 | */ | ||
167 | struct sched_clock_data *my_scd = this_scd(); | 161 | struct sched_clock_data *my_scd = this_scd(); |
168 | 162 | ||
169 | lock_double_clock(scd, my_scd); | 163 | lock_double_clock(scd, my_scd); |
170 | 164 | ||
171 | now += scd->tick_raw - my_scd->tick_raw; | 165 | this_clock = __update_sched_clock(my_scd, now); |
172 | now += my_scd->tick_gtod - scd->tick_gtod; | 166 | remote_clock = scd->clock; |
167 | |||
168 | /* | ||
169 | * Use the opportunity that we have both locks | ||
170 | * taken to couple the two clocks: we take the | ||
171 | * larger time as the latest time for both | ||
172 | * runqueues. (this creates monotonic movement) | ||
173 | */ | ||
174 | if (likely(remote_clock < this_clock)) { | ||
175 | clock = this_clock; | ||
176 | scd->clock = clock; | ||
177 | } else { | ||
178 | /* | ||
179 | * Should be rare, but possible: | ||
180 | */ | ||
181 | clock = remote_clock; | ||
182 | my_scd->clock = remote_clock; | ||
183 | } | ||
173 | 184 | ||
174 | __raw_spin_unlock(&my_scd->lock); | 185 | __raw_spin_unlock(&my_scd->lock); |
175 | } else { | 186 | } else { |
176 | __raw_spin_lock(&scd->lock); | 187 | __raw_spin_lock(&scd->lock); |
188 | clock = __update_sched_clock(scd, now); | ||
177 | } | 189 | } |
178 | 190 | ||
179 | clock = __update_sched_clock(scd, now); | ||
180 | |||
181 | __raw_spin_unlock(&scd->lock); | 191 | __raw_spin_unlock(&scd->lock); |
182 | 192 | ||
183 | return clock; | 193 | return clock; |
@@ -223,7 +233,6 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); | |||
223 | void sched_clock_idle_wakeup_event(u64 delta_ns) | 233 | void sched_clock_idle_wakeup_event(u64 delta_ns) |
224 | { | 234 | { |
225 | struct sched_clock_data *scd = this_scd(); | 235 | struct sched_clock_data *scd = this_scd(); |
226 | u64 now = sched_clock(); | ||
227 | 236 | ||
228 | /* | 237 | /* |
229 | * Override the previous timestamp and ignore all | 238 | * Override the previous timestamp and ignore all |