Re: [PATCH v2 1/2] perf arm-spe: Use SPE data source for neoverse cores

Leo Yan
2022-03-13T11:46:29Z

Hi Ali, German,

On Wed, Mar 02, 2022 at 11:59:05AM +0000, German Gomez wrote:
> Hi Ali,
>
> On 21/02/2022 22:47, Ali Saidi wrote:
> > When synthesizing data from SPE, augment the type with source information
> > for Arm Neoverse cores. The field is IMPLDEF but the Neoverse cores all use
> > the same encoding. I can't find encoding information for any other SPE
> > implementations to unify their choices with Arm's thus that is left for
> > future work.
> >
> > This change populates the mem_lvl_num for Neoverse cores instead of the
> > deprecated mem_lvl namespace.
> >
> > Signed-off-by: Ali Saidi <alisaidi@amazon.com>
> > ---
> > .../util/arm-spe-decoder/arm-spe-decoder.c | 1 +
> > .../util/arm-spe-decoder/arm-spe-decoder.h | 12 ++
> > tools/perf/util/arm-spe.c | 106 +++++++++++++++---
> > 3 files changed, 104 insertions(+), 15 deletions(-)
> >
> > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> > index 5e390a1a79ab..091987dd3966 100644
> > --- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> > @@ -220,6 +220,7 @@ static int arm_spe_read_record(struct arm_spe_decoder *decoder)
> >
> > break;
> > case ARM_SPE_DATA_SOURCE:
> > + decoder->record.source = payload;
> > break;
> > case ARM_SPE_BAD:
> > break;
> > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> > index 69b31084d6be..c81bf90c0996 100644
> > --- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.h
> > @@ -29,6 +29,17 @@ enum arm_spe_op_type {
> > ARM_SPE_ST = 1 << 1,
> > };
> >
> > +enum arm_spe_neoverse_data_source {
> > + ARM_SPE_NV_L1D = 0x0,
> > + ARM_SPE_NV_L2 = 0x8,
> > + ARM_SPE_NV_PEER_CORE = 0x9,
> > + ARM_SPE_NV_LCL_CLSTR = 0xa,
> > + ARM_SPE_NV_SYS_CACHE = 0xb,
> > + ARM_SPE_NV_PEER_CLSTR = 0xc,
> > + ARM_SPE_NV_REMOTE = 0xd,
> > + ARM_SPE_NV_DRAM = 0xe,
> > +};
> > +
> > struct arm_spe_record {
> > enum arm_spe_sample_type type;
> > int err;
> > @@ -40,6 +51,7 @@ struct arm_spe_record {
> > u64 virt_addr;
> > u64 phys_addr;
> > u64 context_id;
> > + u16 source;
> > };
> >
> > struct arm_spe_insn;
> > diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> > index d2b64e3f588b..e0243c2fed5f 100644
> > --- a/tools/perf/util/arm-spe.c
> > +++ b/tools/perf/util/arm-spe.c
> > @@ -34,6 +34,7 @@
> > #include "arm-spe-decoder/arm-spe-decoder.h"
> > #include "arm-spe-decoder/arm-spe-pkt-decoder.h"
> >
> > +#include <../../../arch/arm64/include/asm/cputype.h>
> > #define MAX_TIMESTAMP (~0ULL)
> >
> > struct arm_spe {
> > @@ -45,6 +46,7 @@ struct arm_spe {
> > struct perf_session *session;
> > struct machine *machine;
> > u32 pmu_type;
> > + u64 midr;
> >
> > struct perf_tsc_conversion tc;
> >
> > @@ -399,33 +401,103 @@ static bool arm_spe__is_memory_event(enum arm_spe_sample_type type)
> > return false;
> > }
> >
> > -static u64 arm_spe__synth_data_source(const struct arm_spe_record *record)
> > -{
> > - union perf_mem_data_src data_src = { 0 };
> > +static const struct midr_range neoverse_spe[] = {
> > + MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
> > + MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
> > + {},
> > +};
> >
> > - if (record->op == ARM_SPE_LD)
> > - data_src.mem_op = PERF_MEM_OP_LOAD;
> > - else
> > - data_src.mem_op = PERF_MEM_OP_STORE;
> >
> > +static void arm_spe__synth_data_source_neoverse(const struct arm_spe_record *record,
> > + union perf_mem_data_src *data_src)
> > +{
> > + switch (record->source) {
> > + case ARM_SPE_NV_L1D:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
>
> I understand mem_lvl is deprecated but shouldn't we add the level bits here as well for backwards compat?

Thanks for pointing out this. Yeah, I think German's suggestion is
valid, the commit 6ae5fa61d27d ("perf/x86: Fix data source decoding
for Skylake") introduces new field 'mem_lvl_num', but it also keeps
backwards compatible for the field 'mem_lvl'.

> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_L1;
> > + break;
> > + case ARM_SPE_NV_L2:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_L2;
> > + break;
> > + case ARM_SPE_NV_PEER_CORE:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
> > + data_src->mem_snoop = PERF_MEM_SNOOP_HITM;
> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_ANY_CACHE;

For PEER_CORE data source, we don't know if it's coming from peer
core's L1 cache or L2 cache, right?

If so, do you think if it's possible to retrieve more accurate info
from the field "record->type"?

> > + break;
> > + /*
> > + * We don't know if this is L1, L2, or even L3 (for the cases the system
> > + * has an L3, but we do know it was a cache-2-cache transfer, so set
> > + * SNOOP_HITM
> > + */
> > + case ARM_SPE_NV_LCL_CLSTR:
> > + case ARM_SPE_NV_PEER_CLSTR:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
> > + data_src->mem_snoop = PERF_MEM_SNOOP_HITM;
> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_ANY_CACHE;

Seems to me, we need to add attribution to indicate the difference
between ARM_SPE_NV_PEER_CORE and ARM_SPE_NV_LCL_CLSTR.

For ARM_SPE_NV_PEER_CLSTR data source, should we set any "remote"
attribution as well?

> > + break;
> > + /*
> > + * System cache is assumed to be L4, as cluster cache (if it exists)
> > + * would be L3 cache on Neoverse platforms
> > + */
> > + case ARM_SPE_NV_SYS_CACHE:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_L4;
> > + break;
> > + /*
> > + * We don't know what level it hit in, except it came from the other
> > + * socket
> > + */
> > + case ARM_SPE_NV_REMOTE:
> > + data_src->mem_snoop = PERF_MEM_SNOOP_HITM;
> > + data_src->mem_remote = PERF_MEM_REMOTE_REMOTE;
> > + break;

Just curious, is it possible that 'record->source' combines multiple
bits? Like we can get a data source value with:

ARM_SPE_NV_REMOTE | ARM_SPE_NV_REMOTE

> > + case ARM_SPE_NV_DRAM:
> > + data_src->mem_lvl = PERF_MEM_LVL_HIT;
> > + data_src->mem_lvl_num = PERF_MEM_LVLNUM_RAM;
> > + break;
> > + default:
> > + break;
> > + }
> > +}
> > +
> > +static void arm_spe__synth_data_source_generic(const struct arm_spe_record *record,
> > + union perf_mem_data_src *data_src)
> > +{
> > if (record->type & (ARM_SPE_LLC_ACCESS | ARM_SPE_LLC_MISS)) {
> > - data_src.mem_lvl = PERF_MEM_LVL_L3;
> > + data_src->mem_lvl = PERF_MEM_LVL_L3;
> >
> > if (record->type & ARM_SPE_LLC_MISS)
> > - data_src.mem_lvl |= PERF_MEM_LVL_MISS;
> > + data_src->mem_lvl |= PERF_MEM_LVL_MISS;
> > else
> > - data_src.mem_lvl |= PERF_MEM_LVL_HIT;
> > + data_src->mem_lvl |= PERF_MEM_LVL_HIT;
> > } else if (record->type & (ARM_SPE_L1D_ACCESS | ARM_SPE_L1D_MISS)) {
> > - data_src.mem_lvl = PERF_MEM_LVL_L1;
> > + data_src->mem_lvl = PERF_MEM_LVL_L1;
> >
> > if (record->type & ARM_SPE_L1D_MISS)
> > - data_src.mem_lvl |= PERF_MEM_LVL_MISS;
> > + data_src->mem_lvl |= PERF_MEM_LVL_MISS;
> > else
> > - data_src.mem_lvl |= PERF_MEM_LVL_HIT;
> > + data_src->mem_lvl |= PERF_MEM_LVL_HIT;
> > }
> >
> > if (record->type & ARM_SPE_REMOTE_ACCESS)
> > - data_src.mem_lvl |= PERF_MEM_LVL_REM_CCE1;
> > + data_src->mem_lvl |= PERF_MEM_LVL_REM_CCE1;
> > +}
> > +
> > +static u64 arm_spe__synth_data_source(const struct arm_spe_record *record, u64 midr)
> > +{
> > + union perf_mem_data_src data_src = { 0 };
> > + bool is_neoverse = is_midr_in_range(midr, neoverse_spe);
> > +
> > + if (record->op & ARM_SPE_LD)
> > + data_src.mem_op = PERF_MEM_OP_LOAD;
> > + else
> > + data_src.mem_op = PERF_MEM_OP_STORE;
> > +
> > + if (is_neoverse)
> > + arm_spe__synth_data_source_neoverse(record, &data_src);
> > + else
> > + arm_spe__synth_data_source_generic(record, &data_src);
> >
> > if (record->type & (ARM_SPE_TLB_ACCESS | ARM_SPE_TLB_MISS)) {
> > data_src.mem_dtlb = PERF_MEM_TLB_WK;
> > @@ -446,7 +518,7 @@ static int arm_spe_sample(struct arm_spe_queue *speq)
> > u64 data_src;
> > int err;
> >
> > - data_src = arm_spe__synth_data_source(record);
> > + data_src = arm_spe__synth_data_source(record, spe->midr);
> >
> > if (spe->sample_flc) {
> > if (record->type & ARM_SPE_L1D_MISS) {
> > @@ -796,6 +868,10 @@ static int arm_spe_process_event(struct perf_session *session,
> > u64 timestamp;
> > struct arm_spe *spe = container_of(session->auxtrace,
> > struct arm_spe, auxtrace);
> > + const char *cpuid = perf_env__cpuid(session->evlist->env);
> > + u64 midr = strtol(cpuid, NULL, 16);
> > +
> > + spe->midr = midr;
>
> I think this midr setup belongs in the arm_spe_process_auxtrace_info callback instead.

Yeah, arm_spe_process_event() would be invoked for multiple times for
processing perf events. arm_spe_process_auxtrace_info() would be a
good place to initialize midr.

Thanks,
Leo