Uncore Manual

Reference Number: 329468-002 47
Uncore Performance Monitoring
Cacheing Agent (Cbo) Performance Monitoring
RxR_IRQ_RETRY
• Title: Ingress Request Queue Rejects
• Category: INGRESS_RETRY Events
• Event Code: 0x32
• Max. Inc/Cyc:. 1, Register Restrictions: 0-1
• Definition:
Table 2-29. Unit Masks for RxR_IPQ_RETRY
Extension
umask
[15:8]
Description
ANY bxxxxxxx1 Any Reject
Counts the number of times that a request form the IPQ was
retried because of a TOR reject. TOR rejects from the IPQ can be
caused by the Egress being full or Address Conflicts.
FULL bxxxxxx1x No Egress Credits
Counts the number of times that a request form the IPQ was
retried because of a TOR reject from the Egress being full. IPQ
requests make use of the AD Egress for regular responses, the
BL egress to forward data, and the AK egress to return credits.
ADDR_CONFLICT bxxxxx1xx Address Conflict
Counts the number of times that a request form the IPQ was
retried because of a TOR reject from an address conflicts.
Address conflicts out of the IPQ should be rare. They will
generally only occur if two different sockets are sending requests
to the same address at the same time. This is a true “conflict”
case, unlike the IPQ Address Conflict which is commonly caused
by prefetching characteristics.
QPI_CREDITS bxxx1xxxx No QPI Credits
Table 2-30. Unit Masks for RxR_IRQ_RETRY
Extension
umask
[15:8]
Description
ANY bxxxxxxx1 Any Reject
Counts the number of IRQ retries that occur. Requests from the
IRQ are retried if they are rejected from the TOR pipeline for a
variety of reasons. Some of the most common reasons include if
the Egress is full, there are no RTIDs, or there is a Physical
Address match to another outstanding request.
FULL bxxxxxx1x No Egress Credits
Counts the number of times that a request from the IRQ was
retried because it failed to acquire an entry in the Egress. The
egress is the buffer that queues up for allocating onto the ring.
IRQ requests can make use of all four rings and all four
Egresses. If any of the queues that a given request needs to
make use of are full, the request will be retried.
ADDR_CONFLICT bxxxxx1xx Address Conflict
Counts the number of times that a request from the IRQ was
retried because of an address match in the TOR. In order to
maintain coherency, requests to the same address are not
allowed to pass each other up in the Cbo. Therefore, if there is
an outstanding request to a given address, one cannot issue
another request to that address until it is complete. This comes
up most commonly with prefetches. Outstanding prefetches
occasionally will not complete their memory fetch and a demand
request to the same address will then sit in the IRQ and get
retried until the prefetch fills the data into the LLC. Therefore, it
will not be uncommon to see this case in high bandwidth
streaming workloads when the LLC Prefetcher in the core is
enabled.