Uncore Manual
Uncore Performance Monitoring
Memory Controller (iMC) Performance Monitoring
88 Reference Number: 329468-002
POWER_SELF_REFRESH
• Title: Clock-Enabled Self-Refresh
• Category: POWER Events
• Event Code: 0x43
• Max. Inc/Cyc:. 0, Register Restrictions: 0-3
• Definition: Counts the number of cycles when the iMC is in self-refresh and the iMC still has a
clock. This happens in some package C-states. For example, the PCU may ask the iMC to enter self-
refresh even though some of the cores are still processing. One use of this is for Monroe technology.
Self-refresh is required during package C3 and C6, but there is no clock in the iMC at this time, so it
is not possible to count these cases.
POWER_THROTTLE_CYCLES
• Title: Throttle Cycles for Rank 0
• Category: POWER Events
• Event Code: 0x41
• Max. Inc/Cyc:. 1, Register Restrictions: 0-3
• Definition: Counts the number of cycles while the iMC is being throttled by either thermal con-
straints or by the PCU throttling. It is not possible to distinguish between the two. This can be fil-
tered by rank. If multiple ranks are selected and are being throttled at the same time, the counter
will only increment by 1.
PREEMPTION
• Title: Read Preemption Count
• Category: PREEMPTION Events
• Event Code: 0x08
• Max. Inc/Cyc:. 1, Register Restrictions: 0-3
• Definition: Counts the number of times a read in the iMC preempts another read or write. Gener-
ally reads to an open page are issued ahead of requests to closed pages. This improves the page hit
rate of the system. However, high priority requests can cause pages of active requests to be closed
in order to get them out. This will reduce the latency of the high-priority request at the expense of
lower bandwidth and increased overall average latency.
Table 2-83. Unit Masks for POWER_THROTTLE_CYCLES
Extension
umask
[15:8]
Description
RANK0 bxxxxxxx1 DIMM ID
Thermal throttling is performed per DIMM. We support 3 DIMMs
per channel. This ID allows us to filter by ID.
RANK1 bxxxxxx1x DIMM ID
RANK2 bxxxxx1xx DIMM ID
RANK3 bxxxx1xxx DIMM ID
RANK4 bxxx1xxxx DIMM ID
RANK5 bxx1xxxxx DIMM ID
RANK6 bx1xxxxxx DIMM ID
RANK7 b1xxxxxxx DIMM ID