Re: [PATCH v3] drm/amdgpu: add new trace event for page table update v3

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Am 12.08.20 um 10:15 schrieb Shashank Sharma:
Hello Christian,

On 12/08/20 12:15 pm, Christian König wrote:
Am 12.08.20 um 06:33 schrieb Shashank Sharma:
This patch adds a new trace event to track the PTE update
events. This specific event will provide information like:
- start and end of virtual memory mapping
- HW engine flags for the map
- physical address for mapping

This will be particularly useful for memory profiling tools
(like RMV) which are monitoring the page table update events.

V2: Added physical address lookup logic in trace point
V3: switch to use __dynamic_array
      added nptes int the TPprint arguments list
      added page size in the arg list

Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h | 38 +++++++++++++++++++++++
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c    |  9 ++++--
   2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
index 63e734a125fb..b9aae7983b4b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
@@ -321,6 +321,44 @@ DEFINE_EVENT(amdgpu_vm_mapping, amdgpu_vm_bo_cs,
   	    TP_ARGS(mapping)
   );
+TRACE_EVENT(amdgpu_vm_update_ptes,
+	    TP_PROTO(struct amdgpu_vm_update_params *p,
+		     uint64_t start, uint64_t end,
+		     unsigned int nptes, uint64_t dst,
+		     uint64_t incr, uint64_t flags),
+	TP_ARGS(p, start, end, nptes, dst, incr, flags),
+	TP_STRUCT__entry(
+			 __field(u64, start)
+			 __field(u64, end)
+			 __field(u64, flags)
+			 __field(u64, incr)
+			 __field(unsigned int, nptes)
+			 __dynamic_array(u64, dst, nptes)
+	),
+
+	TP_fast_assign(
+			unsigned int i;
+
+			__entry->start = start;
+			__entry->end = end;
+			__entry->flags = flags;
+			__entry->incr = incr;
+			__entry->nptes = nptes;
+
+			for (i = 0; i < nptes; ++i) {
+				u64 addr = p->pages_addr ? amdgpu_vm_map_gart(
+					p->pages_addr, dst) : dst;
+
+				((u64 *)__get_dynamic_array(dst))[i] = addr;
+				dst += incr;
+			}
+	),
+	TP_printk("seg:0x%010llx-0x%010llx, flags:0x%llx, nptr=%u, pgsz:%llu,"
+		  " dst:\n%s", __entry->start, __entry->end, __entry->flags,
+		  __entry->nptes, __entry->incr,
This is not correct. The increment is NOT the page size, but rather the
page size rounded down to a power of 512+4K.

In other words page size can be 4K, 8K, 16K, 32K, 64K....1M, 2M,
4M....512M, 1G, 2G....

But the increment can only be 4K, 2M, 1G....
Understood. But I think the requirement here is for increment. My understanding is that the tool needs to save the page entries, and for that, it will need start of virtual mem, start of physical mem, mapping size and step to increment the entries. If that's so, we can re-label this entry as "step" instead of "page size". Please let me know if you think it's the right thing to do.

We could stick with the naming increment if that helps, but this can also be derived from the number of destination addresses we have.

On the other hand explicitly mentioning it probably won't hurt us either.

And by the way what does "seg" mean?

Christian.

And do we need the nptes here? We just need it to print the correct
number of destination addresses.
Agree, we don't really need nptes here, I will remove that and send V4.

- Shashank

Regards,
Christian.

+		  __print_array(__get_dynamic_array(dst), __entry->nptes, 8))
+);
+
   TRACE_EVENT(amdgpu_vm_set_ptes,
   	    TP_PROTO(uint64_t pe, uint64_t addr, unsigned count,
   		     uint32_t incr, uint64_t flags, bool direct),
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 71e005cf2952..b5dbb5e8bc61 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1513,17 +1513,22 @@ static int amdgpu_vm_update_ptes(struct amdgpu_vm_update_params *params,
   		do {
   			uint64_t upd_end = min(entry_end, frag_end);
   			unsigned nptes = (upd_end - frag_start) >> shift;
+			uint64_t upd_flags = flags | AMDGPU_PTE_FRAG(frag);
/* This can happen when we set higher level PDs to
   			 * silent to stop fault floods.
   			 */
   			nptes = max(nptes, 1u);
+
+			trace_amdgpu_vm_update_ptes(params, frag_start, upd_end,
+						    nptes, dst, incr,
+						    upd_flags);
   			amdgpu_vm_update_flags(params, pt, cursor.level,
   					       pe_start, dst, nptes, incr,
-					       flags | AMDGPU_PTE_FRAG(frag));
+					       upd_flags);
pe_start += nptes * 8;
-			dst += (uint64_t)nptes * AMDGPU_GPU_PAGE_SIZE << shift;
+			dst += nptes * incr;
frag_start = upd_end;
   			if (frag_start >= frag_end) {

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