From e51ee31e8af22948dcc3b115978469b09c96c3fd Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Wed, 9 Sep 2009 20:28:49 +0000 Subject: [PATCH] powerpc/perf_counters: Reduce stack usage of power_check_constraints Michael Ellerman reported stack-frame size warnings being produced for power_check_constraints(), which uses an 8*8 array of u64 and two 8*8 arrays of unsigned long, which are currently allocated on the stack, along with some other smaller variables. These arrays come to 1.5kB on 64-bit or 1kB on 32-bit, which is a bit too much for the stack. This fixes the problem by putting these arrays in the existing per-cpu cpu_hw_counters struct. This is OK because two of the call sites have interrupts disabled already; for the third call site we use get_cpu_var, which disables preemption, so we know we won't get a context switch while we're in power_check_constraints(). Note that power_check_constraints() can be called during context switch but is not called from interrupts. Reported-by: Michael Ellerman Signed-off-by: Paul Mackerras Cc: --- arch/powerpc/kernel/perf_counter.c | 55 +++++++++++++++++------------- 1 file changed, 32 insertions(+), 23 deletions(-) diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c index ccd6b2135642..7ceefaf3a7f5 100644 --- a/arch/powerpc/kernel/perf_counter.c +++ b/arch/powerpc/kernel/perf_counter.c @@ -32,6 +32,9 @@ struct cpu_hw_counters { unsigned long mmcr[3]; struct perf_counter *limited_counter[MAX_LIMITED_HWCOUNTERS]; u8 limited_hwidx[MAX_LIMITED_HWCOUNTERS]; + u64 alternatives[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; + unsigned long amasks[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; + unsigned long avalues[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; }; DEFINE_PER_CPU(struct cpu_hw_counters, cpu_hw_counters); @@ -239,13 +242,11 @@ static void write_pmc(int idx, unsigned long val) * and see if any combination of alternative codes is feasible. * The feasible set is returned in event[]. */ -static int power_check_constraints(u64 event[], unsigned int cflags[], +static int power_check_constraints(struct cpu_hw_counters *cpuhw, + u64 event[], unsigned int cflags[], int n_ev) { unsigned long mask, value, nv; - u64 alternatives[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; - unsigned long amasks[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; - unsigned long avalues[MAX_HWCOUNTERS][MAX_EVENT_ALTERNATIVES]; unsigned long smasks[MAX_HWCOUNTERS], svalues[MAX_HWCOUNTERS]; int n_alt[MAX_HWCOUNTERS], choice[MAX_HWCOUNTERS]; int i, j; @@ -260,21 +261,23 @@ static int power_check_constraints(u64 event[], unsigned int cflags[], if ((cflags[i] & PPMU_LIMITED_PMC_REQD) && !ppmu->limited_pmc_event(event[i])) { ppmu->get_alternatives(event[i], cflags[i], - alternatives[i]); - event[i] = alternatives[i][0]; + cpuhw->alternatives[i]); + event[i] = cpuhw->alternatives[i][0]; } - if (ppmu->get_constraint(event[i], &amasks[i][0], - &avalues[i][0])) + if (ppmu->get_constraint(event[i], &cpuhw->amasks[i][0], + &cpuhw->avalues[i][0])) return -1; } value = mask = 0; for (i = 0; i < n_ev; ++i) { - nv = (value | avalues[i][0]) + (value & avalues[i][0] & addf); + nv = (value | cpuhw->avalues[i][0]) + + (value & cpuhw->avalues[i][0] & addf); if ((((nv + tadd) ^ value) & mask) != 0 || - (((nv + tadd) ^ avalues[i][0]) & amasks[i][0]) != 0) + (((nv + tadd) ^ cpuhw->avalues[i][0]) & + cpuhw->amasks[i][0]) != 0) break; value = nv; - mask |= amasks[i][0]; + mask |= cpuhw->amasks[i][0]; } if (i == n_ev) return 0; /* all OK */ @@ -285,10 +288,11 @@ static int power_check_constraints(u64 event[], unsigned int cflags[], for (i = 0; i < n_ev; ++i) { choice[i] = 0; n_alt[i] = ppmu->get_alternatives(event[i], cflags[i], - alternatives[i]); + cpuhw->alternatives[i]); for (j = 1; j < n_alt[i]; ++j) - ppmu->get_constraint(alternatives[i][j], - &amasks[i][j], &avalues[i][j]); + ppmu->get_constraint(cpuhw->alternatives[i][j], + &cpuhw->amasks[i][j], + &cpuhw->avalues[i][j]); } /* enumerate all possibilities and see if any will work */ @@ -307,11 +311,11 @@ static int power_check_constraints(u64 event[], unsigned int cflags[], * where k > j, will satisfy the constraints. */ while (++j < n_alt[i]) { - nv = (value | avalues[i][j]) + - (value & avalues[i][j] & addf); + nv = (value | cpuhw->avalues[i][j]) + + (value & cpuhw->avalues[i][j] & addf); if ((((nv + tadd) ^ value) & mask) == 0 && - (((nv + tadd) ^ avalues[i][j]) - & amasks[i][j]) == 0) + (((nv + tadd) ^ cpuhw->avalues[i][j]) + & cpuhw->amasks[i][j]) == 0) break; } if (j >= n_alt[i]) { @@ -333,7 +337,7 @@ static int power_check_constraints(u64 event[], unsigned int cflags[], svalues[i] = value; smasks[i] = mask; value = nv; - mask |= amasks[i][j]; + mask |= cpuhw->amasks[i][j]; ++i; j = -1; } @@ -341,7 +345,7 @@ static int power_check_constraints(u64 event[], unsigned int cflags[], /* OK, we have a feasible combination, tell the caller the solution */ for (i = 0; i < n_ev; ++i) - event[i] = alternatives[i][choice[i]]; + event[i] = cpuhw->alternatives[i][choice[i]]; return 0; } @@ -745,7 +749,7 @@ int hw_perf_group_sched_in(struct perf_counter *group_leader, return -EAGAIN; if (check_excludes(cpuhw->counter, cpuhw->flags, n0, n)) return -EAGAIN; - i = power_check_constraints(cpuhw->events, cpuhw->flags, n + n0); + i = power_check_constraints(cpuhw, cpuhw->events, cpuhw->flags, n + n0); if (i < 0) return -EAGAIN; cpuhw->n_counters = n0 + n; @@ -800,7 +804,7 @@ static int power_pmu_enable(struct perf_counter *counter) cpuhw->flags[n0] = counter->hw.counter_base; if (check_excludes(cpuhw->counter, cpuhw->flags, n0, 1)) goto out; - if (power_check_constraints(cpuhw->events, cpuhw->flags, n0 + 1)) + if (power_check_constraints(cpuhw, cpuhw->events, cpuhw->flags, n0 + 1)) goto out; counter->hw.config = cpuhw->events[n0]; @@ -1005,6 +1009,7 @@ const struct pmu *hw_perf_counter_init(struct perf_counter *counter) unsigned int cflags[MAX_HWCOUNTERS]; int n; int err; + struct cpu_hw_counters *cpuhw; if (!ppmu) return ERR_PTR(-ENXIO); @@ -1083,7 +1088,11 @@ const struct pmu *hw_perf_counter_init(struct perf_counter *counter) cflags[n] = flags; if (check_excludes(ctrs, cflags, n, 1)) return ERR_PTR(-EINVAL); - if (power_check_constraints(events, cflags, n + 1)) + + cpuhw = &get_cpu_var(cpu_hw_counters); + err = power_check_constraints(cpuhw, events, cflags, n + 1); + put_cpu_var(cpu_hw_counters); + if (err) return ERR_PTR(-EINVAL); counter->hw.config = events[n]; -- 2.25.1