On Mon, Jan 19, 2026 at 11:55:53AM +0000, James Clark wrote:
[...]
0 0 0x200 [0x90]: PERF_RECORD_ID_INDEX nr: 4 ... id: 771 idx: 0 cpu: 2 tid: -1 ... id: 772 idx: 1 cpu: 3 tid: -1 ... id: 773 idx: 0 cpu: 2 tid: -1 ... id: 774 idx: 1 cpu: 3 tid: -1
Seems to me that this patch works around the issue by using the CPU ID instead, but event->auxtrace.idx is broken.
I don't think it's a workaround, I think it should have been written this way in the first place.
Agree. Sorry for confusion in my rely.
[...]
@@ -3086,7 +3086,7 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o if (aux_offset >= auxtrace_event->offset && aux_offset + aux_size <= auxtrace_event->offset + auxtrace_event->size) {
struct cs_etm_queue *etmq = etm->queues.queue_array[auxtrace_event->idx].priv;
struct cs_etm_queue *etmq = cs_etm__get_queue(etm, auxtrace_event->cpu);
During decoding, cs_etm allocates its own AUX queues and needs to convert the AUX records into a cs_etm-specific format.
For example:
event_id=405 idx=0 cpu=0 tid=6673 event_id=406 idx=1 cpu=1 tid=6673 event_id=407 idx=2 cpu=3 tid=6673 event_id=408 idx=3 cpu=4 tid=6673 event_id=409 idx=4 cpu=5 tid=6673 ` ` `> CPU ID `> Event ID `> Generic buffer IDs
In this case, I deliberately hotplugged off CPU2. As a result, the buffer IDs are consecutive from 0 to 4, while the CPU ID for CPU2 is missing. When adding AUX records to the cs_etm queues, we need to convert from the generic buffer index to the corresponding CPU ID.
So the above change makes sense to me.
/* * If this AUX event was inside this buffer somewhere, create a new auxtrace event@@ -3095,6 +3095,7 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o auxtrace_fragment.auxtrace = *auxtrace_event; auxtrace_fragment.auxtrace.size = aux_size; auxtrace_fragment.auxtrace.offset = aux_offset;
auxtrace_fragment.auxtrace.idx = etmq->queue_nr;
I am still confused about this. Because above auxtrace will be queued on cs_etm queues, should we convert from the generic buffer index to the cs_etm specific one? E.g.,
auxtrace_fragment.auxtrace.idx = auxtrace_event->cpu;
BTW, if my understanding above is valid, it is good to go through the cs_etm.c file for the "idx <-> CPU ID" conversion.
Thanks, Leo
file_offset += aux_offset - auxtrace_event->offset + auxtrace_event->header.size; pr_debug3("CS ETM: Queue buffer size: %#"PRI_lx64" offset: %#"PRI_lx64-- 2.34.1
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