Uncore Manual

Uncore Performance Monitoring
R3QPI Performance Monitoring
188 Reference Number: 329468-002
VN1_CREDITS_USED
• Title: VN1 Credit Used
• Category: LINK_VN1_CREDITS Events
• Event Code: 0x38
• Max. Inc/Cyc:. 1, Register Restrictions: 0-1
• Definition: Number of times a VN1 credit was used on the DRS message channel. In order for a
request to be transferred across QPI, it must be guaranteed to have a flit buffer on the remote
socket to sink into. There are two credit pools, VNA and VN1. VNA is a shared pool used to achieve
high performance. The VN1 pool has reserved entries for each message class and is used to prevent
deadlock. Requests first attempt to acquire a VNA credit, and then fall back to VN1 if they fail. This
counts the number of times a VN1 credit was used. Note that a single VN1 credit holds access to
potentially multiple flit buffers. For example, a transfer that uses VNA could use 9 flit buffers and in
that case uses 9 credits. A transfer on VN1 will only count a single credit even though it may use
multiple buffers.
VNA_CREDITS_ACQUIRED
• Title: VNA credit Acquisitions
• Category: LINK_VNA_CREDITS Events
• Event Code: 0x33
• Max. Inc/Cyc:. 4, Register Restrictions: 0-1
• Definition: Number of QPI VNA Credit acquisitions. This event can be used in conjunction with the
VNA In-Use Accumulator to calculate the average lifetime of a credit holder. VNA credits are used by
all message classes in order to communicate across QPI. If a packet is unable to acquire credits, it
will then attempt to use credits from the VN0 pool. Note that a single packet may require multiple
flit buffers (i.e. when data is being transferred). Therefore, this event will increment by the number
of credits acquired in each cycle. Filtering based on message class is not provided. One can count
the number of packets transferred in a given message class using an qfclk event.
Table 2-213. Unit Masks for VN1_CREDITS_USED
Extension
umask
[15:8]
Description
HOM bxxxxxxx1 HOM Message Class
Filter for the Home (HOM) message class. HOM is generally used to
send requests, request responses, and snoop responses.
SNP bxxxxxx1x SNP Message Class
Filter for Snoop (SNP) message class. SNP is used for outgoing
snoops. Note that snoop responses flow on the HOM message class.
NDR bxxxxx1xx NDR Message Class
NDR packets are used to transmit a variety of protocol flits including
grants and completions (CMP).
DRS bxxxx1xxx DRS Message Class
Filter for Data Response (DRS). DRS is generally used to transmit
data with coherency. For example, remote reads and writes, or cache
to cache transfers will transmit their data using DRS.
NCB bxxx1xxxx NCB Message Class
Filter for Non-Coherent Broadcast (NCB). NCB is generally used to
transmit data without coherency. For example, non-coherent read
data returns.
NCS bxx1xxxxx NCS Message Class
Filter for Non-Coherent Standard (NCS). NCS is commonly used for