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    SubjectRe: [PATCH] perf cs-etm: Add support for coresight trace for any range of CPUs
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    On 20/04/2023 12:47, Ganapatrao Kulkarni wrote:
    >
    > Hi James,
    >
    > On 20-04-2023 03:13 pm, James Clark wrote:
    >>
    >>
    >> On 19/04/2023 18:21, Ganapatrao Kulkarni wrote:
    >>> The current implementation supports coresight trace for a range of
    >>> CPUs, if the first CPU is CPU0.
    >>>
    >>> Adding changes to enable coresight trace for any range of CPUs by
    >>> decoding the first CPU also from the header.
    >>> Later, first CPU id is used instead of CPU0 across the decoder
    >>> functions.
    >>>
    >>> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
    >>> ---
    >>>   .../perf/util/cs-etm-decoder/cs-etm-decoder.c |  4 +-
    >>>   .../perf/util/cs-etm-decoder/cs-etm-decoder.h |  3 +-
    >>>   tools/perf/util/cs-etm.c                      | 62 ++++++++++++-------
    >>>   3 files changed, 42 insertions(+), 27 deletions(-)
    >>>
    >>> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    >>> b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    >>> index 82a27ab90c8b..41ab299b643b 100644
    >>> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    >>> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
    >>> @@ -724,7 +724,7 @@ cs_etm_decoder__create_etm_decoder(struct
    >>> cs_etm_decoder_params *d_params,
    >>>   }
    >>>     struct cs_etm_decoder *
    >>> -cs_etm_decoder__new(int decoders, struct cs_etm_decoder_params
    >>> *d_params,
    >>> +cs_etm_decoder__new(int first_decoder, int decoders, struct
    >>> cs_etm_decoder_params *d_params,
    >>>               struct cs_etm_trace_params t_params[])
    >>>   {
    >>>       struct cs_etm_decoder *decoder;
    >>> @@ -769,7 +769,7 @@ cs_etm_decoder__new(int decoders, struct
    >>> cs_etm_decoder_params *d_params,
    >>>       /* init raw frame logging if required */
    >>>       cs_etm_decoder__init_raw_frame_logging(d_params, decoder);
    >>>   -    for (i = 0; i < decoders; i++) {
    >>> +    for (i = first_decoder; i < decoders; i++) {
    >>>           ret = cs_etm_decoder__create_etm_decoder(d_params,
    >>>                                &t_params[i],
    >>>                                decoder);
    >>> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
    >>> b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
    >>> index 92a855fbe5b8..b06193fc75b4 100644
    >>> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
    >>> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
    >>> @@ -90,7 +90,8 @@ int cs_etm_decoder__process_data_block(struct
    >>> cs_etm_decoder *decoder,
    >>>                          size_t len, size_t *consumed);
    >>>     struct cs_etm_decoder *
    >>> -cs_etm_decoder__new(int num_cpu,
    >>> +cs_etm_decoder__new(int first_decoder,
    >>> +            int decoders,
    >>>               struct cs_etm_decoder_params *d_params,
    >>>               struct cs_etm_trace_params t_params[]);
    >>>   diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
    >>> index 94e2d02009eb..2619513ae088 100644
    >>> --- a/tools/perf/util/cs-etm.c
    >>> +++ b/tools/perf/util/cs-etm.c
    >>> @@ -55,6 +55,8 @@ struct cs_etm_auxtrace {
    >>>       u8 has_virtual_ts; /* Virtual/Kernel timestamps in the trace. */
    >>>         int num_cpu;
    >>> +    int first_cpu;
    >>> +    int last_cpu;
    >>>       u64 latest_kernel_timestamp;
    >>>       u32 auxtrace_type;
    >>>       u64 branches_sample_type;
    >>> @@ -638,14 +640,13 @@ static void cs_etm__set_trace_param_ete(struct
    >>> cs_etm_trace_params *t_params,
    >>>   }
    >>>     static int cs_etm__init_trace_params(struct cs_etm_trace_params
    >>> *t_params,
    >>> -                     struct cs_etm_auxtrace *etm,
    >>> -                     int decoders)
    >>> +                     struct cs_etm_auxtrace *etm)
    >>>   {
    >>>       int i;
    >>>       u32 etmidr;
    >>>       u64 architecture;
    >>>   -    for (i = 0; i < decoders; i++) {
    >>> +    for (i = etm->first_cpu; i < etm->last_cpu; i++) {
    >>>           architecture = etm->metadata[i][CS_ETM_MAGIC];
    >>>             switch (architecture) {
    >>> @@ -817,7 +818,7 @@ static void cs_etm__free(struct perf_session
    >>> *session)
    >>>       /* Then the RB tree itself */
    >>>       intlist__delete(traceid_list);
    >>>   -    for (i = 0; i < aux->num_cpu; i++)
    >>> +    for (i = aux->first_cpu; i < aux->last_cpu; i++)
    >>>           zfree(&aux->metadata[i]);
    >>>         thread__zput(aux->unknown_thread);
    >>> @@ -921,7 +922,8 @@ static struct cs_etm_queue
    >>> *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
    >>>        * Each queue can only contain data from one CPU when
    >>> unformatted, so only one decoder is
    >>>        * needed.
    >>>        */
    >>> -    int decoders = formatted ? etm->num_cpu : 1;
    >>> +    int first_decoder = formatted ? etm->first_cpu : 0;
    >>> +    int decoders = first_decoder + (formatted ? etm->num_cpu : 1);
    >>>         etmq = zalloc(sizeof(*etmq));
    >>>       if (!etmq)
    >>> @@ -937,7 +939,7 @@ static struct cs_etm_queue
    >>> *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
    >>>       if (!t_params)
    >>>           goto out_free;
    >>>   -    if (cs_etm__init_trace_params(t_params, etm, decoders))
    >>> +    if (cs_etm__init_trace_params(t_params, etm))
    >>>           goto out_free;
    >>>         /* Set decoder parameters to decode trace packets */
    >>> @@ -947,8 +949,7 @@ static struct cs_etm_queue
    >>> *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
    >>>                       formatted))
    >>>           goto out_free;
    >>>   -    etmq->decoder = cs_etm_decoder__new(decoders, &d_params,
    >>> -                        t_params);
    >>> +    etmq->decoder = cs_etm_decoder__new(first_decoder, decoders,
    >>> &d_params, t_params);
    >>>         if (!etmq->decoder)
    >>>           goto out_free;
    >>> @@ -2959,11 +2960,11 @@ static int cs_etm__queue_aux_records(struct
    >>> perf_session *session)
    >>>    * Loop through the ETMs and complain if we find at least one where
    >>> ts_source != 1 (virtual
    >>>    * timestamps).
    >>>    */
    >>> -static bool cs_etm__has_virtual_ts(u64 **metadata, int num_cpu)
    >>> +static bool cs_etm__has_virtual_ts(u64 **metadata, struct
    >>> cs_etm_auxtrace *etm)
    >>>   {
    >>>       int j;
    >>>   -    for (j = 0; j < num_cpu; j++) {
    >>> +    for (j = etm->first_cpu; j < etm->last_cpu; j++) {
    >>>           switch (metadata[j][CS_ETM_MAGIC]) {
    >>>           case __perf_cs_etmv4_magic:
    >>>               if (HAS_PARAM(j, ETMV4, TS_SOURCE) ||
    >>> metadata[j][CS_ETMV4_TS_SOURCE] != 1)
    >>> @@ -2982,13 +2983,14 @@ static bool cs_etm__has_virtual_ts(u64
    >>> **metadata, int num_cpu)
    >>>   }
    >>>     /* map trace ids to correct metadata block, from information in
    >>> metadata */
    >>> -static int cs_etm__map_trace_ids_metadata(int num_cpu, u64 **metadata)
    >>> +static int cs_etm__map_trace_ids_metadata(struct cs_etm_auxtrace *etm)
    >>>   {
    >>>       u64 cs_etm_magic;
    >>> +    u64 **metadata = etm->metadata;
    >>>       u8 trace_chan_id;
    >>>       int i, err;
    >>>   -    for (i = 0; i < num_cpu; i++) {
    >>> +    for (i = etm->first_cpu; i < etm->last_cpu; i++) {
    >>>           cs_etm_magic = metadata[i][CS_ETM_MAGIC];
    >>>           switch (cs_etm_magic) {
    >>>           case __perf_cs_etmv3_magic:
    >>> @@ -3015,12 +3017,13 @@ static int cs_etm__map_trace_ids_metadata(int
    >>> num_cpu, u64 **metadata)
    >>>    * If we found AUX_HW_ID packets, then set any metadata marked as
    >>> unused to the
    >>>    * unused value to reduce the number of unneeded decoders created.
    >>>    */
    >>> -static int cs_etm__clear_unused_trace_ids_metadata(int num_cpu, u64
    >>> **metadata)
    >>> +static int cs_etm__clear_unused_trace_ids_metadata(struct
    >>> cs_etm_auxtrace *etm)
    >>>   {
    >>>       u64 cs_etm_magic;
    >>> +    u64 **metadata = etm->metadata;
    >>>       int i;
    >>>   -    for (i = 0; i < num_cpu; i++) {
    >>> +    for (i = etm->first_cpu; i < etm->last_cpu; i++) {
    >>>           cs_etm_magic = metadata[i][CS_ETM_MAGIC];
    >>>           switch (cs_etm_magic) {
    >>>           case __perf_cs_etmv3_magic:
    >>> @@ -3049,7 +3052,7 @@ int cs_etm__process_auxtrace_info_full(union
    >>> perf_event *event,
    >>>       int event_header_size = sizeof(struct perf_event_header);
    >>>       int total_size = auxtrace_info->header.size;
    >>>       int priv_size = 0;
    >>> -    int num_cpu;
    >>> +    int num_cpu, first_cpu = 0, last_cpu;
    >>>       int err = 0;
    >>>       int aux_hw_id_found;
    >>>       int i, j;
    >>> @@ -3068,22 +3071,31 @@ int cs_etm__process_auxtrace_info_full(union
    >>> perf_event *event,
    >>>       /* First the global part */
    >>>       ptr = (u64 *) auxtrace_info->priv;
    >>>       num_cpu = ptr[CS_PMU_TYPE_CPUS] & 0xffffffff;
    >>> -    metadata = zalloc(sizeof(*metadata) * num_cpu);
    >>> +
    >>> +    /* Start parsing after the common part of the header */
    >>> +    i = CS_HEADER_VERSION_MAX;
    >>> +
    >>> +    /*Get CPU id of first event */
    >>> +    first_cpu = ptr[i + CS_ETM_CPU];
    >>> +    last_cpu = first_cpu + num_cpu;
    >>> +
    >>> +    if (first_cpu > cpu__max_cpu().cpu ||
    >>> +            last_cpu > cpu__max_cpu().cpu)
    >>> +        return -EINVAL;
    >>> +
    >>> +    metadata = zalloc(sizeof(*metadata) * last_cpu);
    >>
    >> Hi Ganapatrao,
    >>
    >> I think I see what the problem is, but I'm wondering if a better fix
    >> would be to further decouple the CPU ID from the index in the array.
    >>
    >> With your change it's not clear what happens with sparse recordings, for
    >> example 'perf record -e cs_etm// -C 1,3,5'. And it seems like there is
    >
    > This patch fixes for any range of CPUs.
    > Record with sparse list of CPUs will not work with current code still.
    >

    Is there a major issue that means sparse can't be done? I'm thinking it
    would be best to fix both issues with one change while we understand
    this part rather than a half fix that might have do be completely
    re-understood and re-done later anyway. Unless there is some big blocker
    but I can't see it?

    >> some wastage in the zalloc here for example if only CPU 256 is traced
    >> then we'd still make 256 decoders but 255 of them would be unused?
    >>
    >> I tried to test sparse recordings, but your change doesn't apply to the
    >> latest coresight/next branch. I did notice that 'perf report -D' doesn't
    >> work with them on coresight/next (it just quits), but I couldn't see if
    >> that's fixed with your change.
    >
    > My patch is rebased on 6.3-RC7 codebase with Mike's 3 perf patches
    > related to dynamic id [1] support(queued for 6.4).
    >
    > "perf report -D" works for me.

    I was referring to sparse CPU lists, which I think you mentioned above
    doesn't work even with this patch.

    >
    > [1] https://www.spinics.net/lists/linux-perf-users/msg27452.html
    >

    It should be based on the next branch here:
    git://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git

    >>
    >> Would a better fix not be to keep the metadata loops from 0-N and
    >> instead save the CPU ID in cs_etm_decoder_params or the decoder. That
    >> way it would support both sparse and not starting from 0 cases? I think
    >
    > Yep, I though this initially, it got complicated due to for more
    > for-loops. I will try again and post V2.
    >

    I can't imagine it would need any extra for loops off the top of my
    head. Just saving the CPU ID in a few structs and using it wherever it's
    needed instead of the loop index. I imagine most of the loops would
    actually stay the same rather than be changed like you have in V1.

    >> the code would be better if it's worded like "i < recorded_cpus" rather
    >> than "i < cpu" to make it clear that i isn't actually the CPU ID it's
    >> just an index.
    >
    > Yes, makes sense to call it "recorded_cpus".
    >
    >>
    >> Also a new test for this scenario would probably be a good idea.
    >>
    >> Thanks
    >> James
    >>
    > Thanks,
    > Ganapat

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