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Date: Wed, 26 Nov 2008 16:20:40 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: eranian@...glemail.com
cc: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
mingo@...e.hu, x86@...nel.org, andi@...stfloor.org,
eranian@...il.com, sfr@...b.auug.org.au
Subject: Re: [patch 22/24] perfmon: AMD64 processor support (x86)
On Wed, 26 Nov 2008, eranian@...glemail.com wrote:
> +static struct pfm_regmap_desc pfm_amd64_pmc_desc[] = {
> +/* pmc0 */ PMC_D(PFM_REG_I64, "PERFSEL0", PFM_K8_VAL, PFM_K8_RSVD, PFM_K8_NO64, MSR_K7_EVNTSEL0),
> +/* pmc1 */ PMC_D(PFM_REG_I64, "PERFSEL1", PFM_K8_VAL, PFM_K8_RSVD, PFM_K8_NO64, MSR_K7_EVNTSEL1),
> +/* pmc2 */ PMC_D(PFM_REG_I64, "PERFSEL2", PFM_K8_VAL, PFM_K8_RSVD, PFM_K8_NO64, MSR_K7_EVNTSEL2),
> +/* pmc3 */ PMC_D(PFM_REG_I64, "PERFSEL3", PFM_K8_VAL, PFM_K8_RSVD, PFM_K8_NO64, MSR_K7_EVNTSEL3),
Why is PMC_D defined in include/linux/perfmon_pmu.h and only used here ?
> +static int pfm_amd64_acquire_nb(struct pfm_context *ctx)
> +{
> + struct pfm_context **entry, *old;
> + int proc_id;
> +
> +#ifdef CONFIG_SMP
> + proc_id = cpu_data(smp_processor_id()).phys_proc_id;
> +#else
> + proc_id = 0;
> +#endif
And the actual vaule of proc_id aside of generating a compiler warning
is ?
> +/**
> + * pfm_amd64_pmc_write_check -- check validity of pmc writes
> + * @ctx: context to use
> + * @set: event set to use
> + * @req: user request to modify the pmc
> + *
> + * invoked from pfm_write_pmcs() when pfm_nb_sys_owners is not NULL,i.e.,
> + * when we have detected a multi-core processor.
> + *
> + * context is locked, interrupts are masked
> + */
> +static int pfm_amd64_pmc_write_check(struct pfm_context *ctx,
> + struct pfm_event_set *set,
> + struct pfarg_pmr *req)
> +{
> + unsigned int event;
> +
> + /*
> + * delay checking NB event until we load the context
> + */
> + if (ctx->state == PFM_CTX_UNLOADED)
> + return 0;
> +
> + /*
> + * check event is NB event
> + */
> + event = (unsigned int)(req->reg_value & 0xff);
> + if (event < 0xee)
Magic 0xee means what ?
> +/**
> + * pfm_amd64_unload_context -- amd64 mdoels-specific unload callback
> + * @ctx: context to use
> + *
> + * invoked on pfm_unload_context()
> + */
> +static void pfm_amd64_unload_context(struct pfm_context *ctx)
> +{
> + struct pfm_context **entry, *old;
> + int proc_id;
> +
> +#ifdef CONFIG_SMP
> + proc_id = cpu_data(smp_processor_id()).phys_proc_id;
> +#else
> + proc_id = 0;
> +#endif
See above.
> + pfm_arch_bv_set_bit(0, enable_mask);
> + pfm_arch_bv_set_bit(1, enable_mask);
> + pfm_arch_bv_set_bit(2, enable_mask);
> + pfm_arch_bv_set_bit(3, enable_mask);
> + max_enable = 3+1;
Nifty.
> +static int pfm_amd64_setup_nb_event_ctrl(void)
__init ?
> +static void pfm_amd64_setup_registers(void)
Ditto.
> +static int pfm_amd64_probe_pmu(void)
Ditto.
> +/**
> + * pfm_amd64_stop_save - stop monitoring, collect pending overflows
> + * @ctx: context to use
> + * @set: event set to stop
> + *
> + * interrupts are masked, PMU access guaranteed
> + */
> +static int pfm_amd64_stop_save(struct pfm_context *ctx,
> + struct pfm_event_set *set)
> +{
> + struct pfm_arch_pmu_info *pmu_info;
> + u64 used_mask[PFM_PMC_BV];
> + u64 *cnt_pmds;
> + u64 val, wmask, ovfl_mask;
> + u32 i, count;
> +
> + pmu_info = pfm_pmu_info();
We go via a global variable to get a pointer to pfm_amd64_pmu_info,
right ?
> + wmask = 1ULL << pfm_pmu_conf->counter_width;
> +
> + pfm_arch_bv_and(used_mask,
> + set->used_pmcs,
> + enable_mask,
> + max_enable);
> +
> + count = pfm_arch_bv_weight(used_mask, max_enable);
See comments on intel
> + /*
> + * stop monitoring
> + * Unfortunately, this is very expensive!
> + * wrmsrl() is serializing.
> + */
> + for (i = 0; count; i++) {
> + if (pfm_arch_bv_test_bit(i, used_mask)) {
> + wrmsrl(pfm_pmu_conf->pmc_desc[i].hw_addr, 0);
> + count--;
> + }
> + }
> +
> + /*
> + * if we already having a pending overflow condition, we simply
> + * return to take care of this first.
> + */
> + if (set->npend_ovfls)
> + return 1;
Ditto.
> +/**
> + * pfm_amd64_quiesce_pmu -- stop monitoring without grabbing any lock
> + *
> + * called from NMI interrupt handler to immediately stop monitoring
> + * cannot grab any lock, including perfmon related locks
And can race against some other code modifying the msrs
> + */
> +static void __kprobes pfm_amd64_quiesce(void)
> +{
> + /*
> + * quiesce PMU by clearing available registers that have
> + * the start/stop capability
> + */
> + if (pfm_arch_bv_test_bit(0, pfm_pmu_conf->regs_all.pmcs))
> + wrmsrl(MSR_K7_EVNTSEL0, 0);
> + if (pfm_arch_bv_test_bit(1, pfm_pmu_conf->regs_all.pmcs))
> + wrmsrl(MSR_K7_EVNTSEL0+1, 0);
> + if (pfm_arch_bv_test_bit(2, pfm_pmu_conf->regs_all.pmcs))
> + wrmsrl(MSR_K7_EVNTSEL0+2, 0);
> + if (pfm_arch_bv_test_bit(3, pfm_pmu_conf->regs_all.pmcs))
> + wrmsrl(MSR_K7_EVNTSEL0+3, 0);
> +}
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