Messages in this thread | | | Date | Wed, 21 Apr 2010 10:44:58 +0200 | Subject | Re: [RFC] perf_events: support for uncore a.k.a. nest units | From | stephane eranian <> |
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On Wed, Apr 21, 2010 at 10:39 AM, Lin Ming <ming.m.lin@intel.com> wrote: > On Wed, 2010-04-21 at 16:32 +0800, stephane eranian wrote: >> Seems to me that struct pmu is a shared resource across all CPUs. >> I don't understand why scheduling on one CPU would have to impact >> all the other CPUs, unless I am missing something here. > > Do you mean the pmu->flag?
Yes.
> You are right, pmu->flag should be per cpu data. > > Will update the patch. > > Thanks, > Lin Ming > >> >> >> On Wed, Apr 21, 2010 at 10:08 AM, Lin Ming <ming.m.lin@intel.com> wrote: >> > On Tue, 2010-04-20 at 20:03 +0800, Peter Zijlstra wrote: >> >> On Tue, 2010-04-20 at 19:55 +0800, Lin Ming wrote: >> >> >> >> > > One thing not on that list, which should happen first I guess, is to >> >> > > remove hw_perf_group_sched_in(). The idea is to add some sort of >> >> > > transactional API to the struct pmu, so that we can delay the >> >> > > schedulability check until commit time (and roll back when it fails). >> >> > > >> >> > > Something as simple as: >> >> > > >> >> > > struct pmu { >> >> > > void start_txn(struct pmu *); >> >> > > void commit_txn(struct pmu *); >> >> > > >> >> > > ,,, >> >> > > }; >> >> > >> >> > Could you please explain a bit more? >> >> > >> >> > Does it mean that "start_txn" perform the schedule events stuff >> >> > and "commit_txn" perform the assign events stuff? >> >> > >> >> > Does "commit time" mean the actual activation in hw_perf_enable? >> >> >> >> No, the idea behind hw_perf_group_sched_in() is to not perform >> >> schedulability tests on each event in the group, but to add the group as >> >> a whole and then perform one test. >> >> >> >> Of course, when that test fails, you'll have to roll-back the whole >> >> group again. >> >> >> >> So start_txn (or a better name) would simply toggle a flag in the pmu >> >> implementation that will make pmu::enable() not perform the >> >> schedulablilty test. >> >> >> >> Then commit_txn() will perform the schedulability test (so note the >> >> method has to have a !void return value, my mistake in the earlier >> >> email). >> >> >> >> This will allow us to use the regular >> >> kernel/perf_event.c::group_sched_in() and all the rollback code. >> >> Currently each hw_perf_group_sched_in() implementation duplicates all >> >> the rolllback code (with various bugs). >> >> >> >> >> >> >> >> We must get rid of all weak hw_perf_*() functions before we can properly >> >> consider multiple struct pmu implementations. >> >> >> > >> > Thanks for the clear explanation. >> > >> > Does below patch show what you mean? >> > >> > I only touch the x86 arch code now. >> > >> > --- >> > arch/x86/kernel/cpu/perf_event.c | 161 +++++++++++-------------------------- >> > include/linux/perf_event.h | 10 ++- >> > kernel/perf_event.c | 28 +++---- >> > 3 files changed, 67 insertions(+), 132 deletions(-) >> > >> > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c >> > index 626154a..62aa9a1 100644 >> > --- a/arch/x86/kernel/cpu/perf_event.c >> > +++ b/arch/x86/kernel/cpu/perf_event.c >> > @@ -944,6 +944,9 @@ static int x86_pmu_enable(struct perf_event *event) >> > if (n < 0) >> > return n; >> > >> > + if (!(event->pmu->flag & PERF_EVENT_TRAN_STARTED)) >> > + goto out; >> > + >> > ret = x86_pmu.schedule_events(cpuc, n, assign); >> > if (ret) >> > return ret; >> > @@ -953,6 +956,7 @@ static int x86_pmu_enable(struct perf_event *event) >> > */ >> > memcpy(cpuc->assign, assign, n*sizeof(int)); >> > >> > +out: >> > cpuc->n_events = n; >> > cpuc->n_added += n - n0; >> > >> > @@ -1210,119 +1214,6 @@ x86_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event) >> > return &unconstrained; >> > } >> > >> > -static int x86_event_sched_in(struct perf_event *event, >> > - struct perf_cpu_context *cpuctx) >> > -{ >> > - int ret = 0; >> > - >> > - event->state = PERF_EVENT_STATE_ACTIVE; >> > - event->oncpu = smp_processor_id(); >> > - event->tstamp_running += event->ctx->time - event->tstamp_stopped; >> > - >> > - if (!is_x86_event(event)) >> > - ret = event->pmu->enable(event); >> > - >> > - if (!ret && !is_software_event(event)) >> > - cpuctx->active_oncpu++; >> > - >> > - if (!ret && event->attr.exclusive) >> > - cpuctx->exclusive = 1; >> > - >> > - return ret; >> > -} >> > - >> > -static void x86_event_sched_out(struct perf_event *event, >> > - struct perf_cpu_context *cpuctx) >> > -{ >> > - event->state = PERF_EVENT_STATE_INACTIVE; >> > - event->oncpu = -1; >> > - >> > - if (!is_x86_event(event)) >> > - event->pmu->disable(event); >> > - >> > - event->tstamp_running -= event->ctx->time - event->tstamp_stopped; >> > - >> > - if (!is_software_event(event)) >> > - cpuctx->active_oncpu--; >> > - >> > - if (event->attr.exclusive || !cpuctx->active_oncpu) >> > - cpuctx->exclusive = 0; >> > -} >> > - >> > -/* >> > - * Called to enable a whole group of events. >> > - * Returns 1 if the group was enabled, or -EAGAIN if it could not be. >> > - * Assumes the caller has disabled interrupts and has >> > - * frozen the PMU with hw_perf_save_disable. >> > - * >> > - * called with PMU disabled. If successful and return value 1, >> > - * then guaranteed to call perf_enable() and hw_perf_enable() >> > - */ >> > -int hw_perf_group_sched_in(struct perf_event *leader, >> > - struct perf_cpu_context *cpuctx, >> > - struct perf_event_context *ctx) >> > -{ >> > - struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); >> > - struct perf_event *sub; >> > - int assign[X86_PMC_IDX_MAX]; >> > - int n0, n1, ret; >> > - >> > - if (!x86_pmu_initialized()) >> > - return 0; >> > - >> > - /* n0 = total number of events */ >> > - n0 = collect_events(cpuc, leader, true); >> > - if (n0 < 0) >> > - return n0; >> > - >> > - ret = x86_pmu.schedule_events(cpuc, n0, assign); >> > - if (ret) >> > - return ret; >> > - >> > - ret = x86_event_sched_in(leader, cpuctx); >> > - if (ret) >> > - return ret; >> > - >> > - n1 = 1; >> > - list_for_each_entry(sub, &leader->sibling_list, group_entry) { >> > - if (sub->state > PERF_EVENT_STATE_OFF) { >> > - ret = x86_event_sched_in(sub, cpuctx); >> > - if (ret) >> > - goto undo; >> > - ++n1; >> > - } >> > - } >> > - /* >> > - * copy new assignment, now we know it is possible >> > - * will be used by hw_perf_enable() >> > - */ >> > - memcpy(cpuc->assign, assign, n0*sizeof(int)); >> > - >> > - cpuc->n_events = n0; >> > - cpuc->n_added += n1; >> > - ctx->nr_active += n1; >> > - >> > - /* >> > - * 1 means successful and events are active >> > - * This is not quite true because we defer >> > - * actual activation until hw_perf_enable() but >> > - * this way we* ensure caller won't try to enable >> > - * individual events >> > - */ >> > - return 1; >> > -undo: >> > - x86_event_sched_out(leader, cpuctx); >> > - n0 = 1; >> > - list_for_each_entry(sub, &leader->sibling_list, group_entry) { >> > - if (sub->state == PERF_EVENT_STATE_ACTIVE) { >> > - x86_event_sched_out(sub, cpuctx); >> > - if (++n0 == n1) >> > - break; >> > - } >> > - } >> > - return ret; >> > -} >> > - >> > #include "perf_event_amd.c" >> > #include "perf_event_p6.c" >> > #include "perf_event_p4.c" >> > @@ -1454,6 +1345,47 @@ static inline void x86_pmu_read(struct perf_event *event) >> > x86_perf_event_update(event); >> > } >> > >> > +/* >> > + * Set the flag to make pmu::enable() not perform the >> > + * schedulablilty test. >> > + */ >> > +static void x86_pmu_start_txn(struct pmu *pmu) >> > +{ >> > + pmu->flag |= PERF_EVENT_TRAN_STARTED; >> > +} >> > + >> > +static void x86_pmu_stop_txn(struct pmu *pmu) >> > +{ >> > + pmu->flag &= ~PERF_EVENT_TRAN_STARTED; >> > +} >> > + >> > +/* >> > + * Return 0 if commit transaction success >> > + */ >> > +static int x86_pmu_commit_txn(struct pmu *pmu) >> > +{ >> > + struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); >> > + int assign[X86_PMC_IDX_MAX]; >> > + int n, ret; >> > + >> > + n = cpuc->n_events; >> > + >> > + if (!x86_pmu_initialized()) >> > + return -EAGAIN; >> > + >> > + ret = x86_pmu.schedule_events(cpuc, n, assign); >> > + if (ret) >> > + return ret; >> > + >> > + /* >> > + * copy new assignment, now we know it is possible >> > + * will be used by hw_perf_enable() >> > + */ >> > + memcpy(cpuc->assign, assign, n*sizeof(int)); >> > + >> > + return 0; >> > +} >> > + >> > static const struct pmu pmu = { >> > .enable = x86_pmu_enable, >> > .disable = x86_pmu_disable, >> > @@ -1461,6 +1393,9 @@ static const struct pmu pmu = { >> > .stop = x86_pmu_stop, >> > .read = x86_pmu_read, >> > .unthrottle = x86_pmu_unthrottle, >> > + .start_txn = x86_pmu_start_txn, >> > + .stop_txn = x86_pmu_stop_txn, >> > + .commit_txn = x86_pmu_commit_txn, >> > }; >> > >> > /* >> > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >> > index bf896d0..93aa8d8 100644 >> > --- a/include/linux/perf_event.h >> > +++ b/include/linux/perf_event.h >> > @@ -524,6 +524,8 @@ struct hw_perf_event { >> > >> > struct perf_event; >> > >> > +#define PERF_EVENT_TRAN_STARTED 1 >> > + >> > /** >> > * struct pmu - generic performance monitoring unit >> > */ >> > @@ -534,6 +536,11 @@ struct pmu { >> > void (*stop) (struct perf_event *event); >> > void (*read) (struct perf_event *event); >> > void (*unthrottle) (struct perf_event *event); >> > + void (*start_txn) (struct pmu *pmu); >> > + void (*stop_txn) (struct pmu *pmu); >> > + int (*commit_txn) (struct pmu *pmu); >> > + >> > + u8 flag; >> > }; >> > >> > /** >> > @@ -799,9 +806,6 @@ extern void perf_disable(void); >> > extern void perf_enable(void); >> > extern int perf_event_task_disable(void); >> > extern int perf_event_task_enable(void); >> > -extern int hw_perf_group_sched_in(struct perf_event *group_leader, >> > - struct perf_cpu_context *cpuctx, >> > - struct perf_event_context *ctx); >> > extern void perf_event_update_userpage(struct perf_event *event); >> > extern int perf_event_release_kernel(struct perf_event *event); >> > extern struct perf_event * >> > diff --git a/kernel/perf_event.c b/kernel/perf_event.c >> > index 07b7a43..4537676 100644 >> > --- a/kernel/perf_event.c >> > +++ b/kernel/perf_event.c >> > @@ -83,14 +83,6 @@ extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event) >> > void __weak hw_perf_disable(void) { barrier(); } >> > void __weak hw_perf_enable(void) { barrier(); } >> > >> > -int __weak >> > -hw_perf_group_sched_in(struct perf_event *group_leader, >> > - struct perf_cpu_context *cpuctx, >> > - struct perf_event_context *ctx) >> > -{ >> > - return 0; >> > -} >> > - >> > void __weak perf_event_print_debug(void) { } >> > >> > static DEFINE_PER_CPU(int, perf_disable_count); >> > @@ -642,14 +634,13 @@ group_sched_in(struct perf_event *group_event, >> > struct perf_event_context *ctx) >> > { >> > struct perf_event *event, *partial_group; >> > + struct pmu *pmu = (struct pmu *)group_event->pmu; >> > int ret; >> > >> > if (group_event->state == PERF_EVENT_STATE_OFF) >> > return 0; >> > >> > - ret = hw_perf_group_sched_in(group_event, cpuctx, ctx); >> > - if (ret) >> > - return ret < 0 ? ret : 0; >> > + pmu->start_txn(pmu); >> > >> > if (event_sched_in(group_event, cpuctx, ctx)) >> > return -EAGAIN; >> > @@ -664,16 +655,21 @@ group_sched_in(struct perf_event *group_event, >> > } >> > } >> > >> > - return 0; >> > + ret = pmu->commit_txn(pmu); >> > + if (!ret) { >> > + pmu->stop_txn(pmu); >> > + return 0; >> > + } >> > >> > group_error: >> > + pmu->stop_txn(pmu); >> > + >> > /* >> > - * Groups can be scheduled in as one unit only, so undo any >> > - * partial group before returning: >> > + * Commit transaction fails, rollback >> > + * Groups can be scheduled in as one unit only, so undo >> > + * whole group before returning: >> > */ >> > list_for_each_entry(event, &group_event->sibling_list, group_entry) { >> > - if (event == partial_group) >> > - break; >> > event_sched_out(event, cpuctx, ctx); >> > } >> > event_sched_out(group_event, cpuctx, ctx); >> > >> > >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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