Uncore Manual

Uncore Performance Monitoring
R3QPI Performance Monitoring
186 Reference Number: 329468-002
• Definition: Number of times a request failed to acquire a DRS VN0 credit. 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 VN0. VNA is a shared pool used to achieve high perfor-
mance. The VN0 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 VN0 if they fail. This therefore
counts the number of times when a request failed to acquire either a VNA or VN0 credit and is
delayed. This should generally be a rare situation.
VN0_CREDITS_USED
• Title: VN0 Credit Used
• Category: LINK_VN0_CREDITS Events
• Event Code: 0x36
• Max. Inc/Cyc:. 1, Register Restrictions: 0-1
• Definition: Number of times a VN0 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 VN0. VNA is a shared pool used to achieve
high performance. The VN0 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 VN0 if they fail. This
counts the number of times a VN0 credit was used. Note that a single VN0 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 VN0 will only count a single credit even though it may use
multiple buffers.
Table 2-210. Unit Masks for VN0_CREDITS_REJECT
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
Table 2-211. Unit Masks for VN0_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).