| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <1271837295.3794.3.camel@minggr.sh.intel.com>
Date: Wed, 21 Apr 2010 16:08:14 +0800
From: Lin Ming <ming.m.lin@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "Gary.Mohr@...l.com" <Gary.Mohr@...l.com>,
Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
Stephane Eranian <eranian@...glemail.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] perf_events: support for uncore a.k.a. nest units
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@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists