First Version of Intel PCT Getting Started by louie-tsai · Pull Request #37 · intel/optimization-zone

louie-tsai · 2026-06-23T07:56:39Z

Guide users how to check PCT status and configure PCT for their workloads such as AI inference using vLLM

The Getting Started matches the contents of Intel PCT tech article.
https://www.intel.com/content/www/us/en/content-details/846906/priority-core-turbo-technology-pct-technology-technical-article.html

Signed-off-by: louie-tsai <louie.tsai@intel.com>

Added a frequency diagram for Xeon 6776P with PCT on and updated the PCT validation instructions.

louie-tsai · 2026-06-24T01:52:51Z

@rsiyer-intel
please help to review the PR. thanks

rsiyer-intel · 2026-06-25T22:48:00Z

+✅ CLOS0 CPU count exactly matches the bucket-0 PCT logical budget.
+```
+
+## 4. Benchmark CLOS0 CPUs with Host PerfSpect


Please provide link to PerfSpect, users may not be aware of this tool https://github.com/intel/PerfSpect
When you say Host PerfSpect, please clarify it as "Benchmark CLOS0 CPUs with PerfSpect tool on the host" (there is no separate Host and Container PerfSpect)

Thanks. I changed title accordingly.
I also have how to install perfspect in folded Details section.
Hope the information works.

rsiyer-intel · 2026-06-25T22:58:16Z

+docker compose --progress=plain --profile set up --abort-on-container-exit
+docker compose --progress=plain --profile check up --abort-on-container-exit
+
+./run_host_perfspect_benchmark.sh


Please make this a link to the script.

can't add link in code snapshot section, so added the link in the sentence above code snapshot section. hope it works

rsiyer-intel · 2026-06-25T23:04:13Z

+This is the frequency diagram on Xeon 6776P with PCT on. 
+<img width="835" height="483" alt="image" src="https://github.com/user-attachments/assets/96f8855c-4b83-4c62-a0dd-fa2408f979fb" />
+
+This is the expected pattern: small active core counts hold the highest PCT turbo


Please clarify that the frequency reported is the frequency when "X" number of cores are active. Can you elaborate what the user needs to understand from above image? Should they be looking at 1-8 cores being active? Are you referring to the SSE frequencies ? They should be ignoring SSE(expected) row.

Frequency steps down as more cores are active, because the average of all the cores is taken ? CLOS0 cores will always operate at higher frequency, no matter how many cores are active?

Since we use CPU as head node, we normally don't use AVX512 or AMX on CPUs for GPU workload, so we look into SSE. more CPU cores are active and frequency will go down. CLOS0 CPU still share the power with other CPUs in the same power domain, so CLOS0 CPU frequency will also go down when CLOS2/3 CPUs start active. You could see frequency when CPU Core count > 8, frequency drops when it starts using CLOS2/3 CPUs.

rsiyer-intel · 2026-06-25T23:06:11Z

+
+## Overview
+
+**Intel® Priority Core Turbo (PCT)** is part of **Intel® Speed Select Technology – Turbo Frequency (SST-TF)**.


If you have any public links to Intel Speed Select Technology, please add it here.

good idea. added links for PCT, SST, and SST-TF. thanks

rsiyer-intel · 2026-06-25T23:13:34Z

+
+### PCT bucket-count interpretation
+
+`intel-speed-select turbo-freq info -l <level>` may print the same `bucket-0`,


Can you share how user can download or get the intel-speed-select tool ? I dont think it is covered prior to this.
And show a sample output of info -l ?

I see that intel-speed-select is part of the Dockerfile. We should probably have this section after the build section and after tool is introduced.

I think in general it would be good to have a section preceding PCT bucket-count interpretation that discusses the different software projects that are required/available for PCT, where to get them, and how to install them (even if it's just a reference to scripts used later in the document).

@rsiyer-intel feel better to explain PCT first, and then help on env setup later. added a refer link to build section in the beginning of the seciton.

@adgubrud we interpretate for users and then set it according to numa topology in pct_map_and_set_clos.sh there are just some background knowledge. users don't need to do anything themselves for that interpretation. hope it address your quesiton

@louie-tsai I think I understand the SW requirements a bit better now and my previous comment doesn't apply anymore.

What I'm trying to get at is that a user will likely be coming into this article with no understanding of how to achieve the steps you're outlining. If you mention in the overview that this guide provides a Docker container and supporting scripts without any extra software dependencies, it will be helpful to provide that context.

rsiyer-intel · 2026-06-25T23:32:20Z

+PCT_TOTAL_LOGICAL_CPUS=32
+```
+
+But the `turbo-freq` output shows two reporting anchors per package:


Will be good to specify that this is a 2S 64c per socket - Intel Xeon 6776P system.

added it accordingly

rsiyer-intel · 2026-06-25T23:38:25Z

+Export the kernel build variables first:
+
+```bash
+source ./set_kernel_env.sh


Can you mention minimum kernel requirement in the main README itself ?
echo "WARN: validated GNR PCT flow expects KERNEL_MM=6.8 and KERNEL_TAG=v6.8." >&2

actually, no minimum kernel. 6.8 just default one. when user runs set_kernel_env.sh, it will update env based on their kernel version.

adgubrud · 2026-06-29T22:57:23Z

+
+This is particularly effective for **GPU-accelerated AI inference**, where a small number of CPU threads handle
+**latency-critical, mostly serial tasks** such as tokenization, scheduling, and feeding GPUs.
+Running these threads on **High-Priority (HP) cores** improves GPU utilization, TTFT, and tail latency.


Please include the expanded version of TTFT. It should be time-to-first-token, right?

yes. added it accordingly. thanks

adgubrud · 2026-06-29T23:04:48Z

+
+### PCT bucket-count interpretation
+
+`intel-speed-select turbo-freq info -l <level>` may print the same `bucket-0`,


I think in general it would be good to have a section preceding PCT bucket-count interpretation that discusses the different software projects that are required/available for PCT, where to get them, and how to install them (even if it's just a reference to scripts used later in the document).

adgubrud · 2026-06-29T23:05:47Z

+### PCT bucket-count interpretation
+
+`intel-speed-select turbo-freq info -l <level>` may print the same `bucket-0`,
+`bucket-1`, and `bucket-2` SST-TF table under multiple `powerdomain-*` anchors.


Please include a quick description of what a powerdomain anchor is

added it accordingly

adgubrud · 2026-06-29T23:08:30Z

+
+For Intel® Xeon® 6776P system, `bucket-0` reports:
+
+```text


Please include the command that produces this output

it is output from check_status script. added some explanation there.

Please see my alternate suggestion above

adgubrud · 2026-06-29T23:08:50Z

+
+But the `turbo-freq` output shows two reporting anchors per package:
+
+```text


Please include the command that produces this output

it is parsed results. no direct command to get it. we handle it all in our script.

adgubrud · 2026-06-29T23:11:28Z

+0-3,32-35,64-67,96-99,128-131,160-163,192-195,224-227
+```
+
+This is the default strict bucket-0 PCT placement used by the updated set script.


Is the updated set script "set_kernel_env.sh"? Please link to whichever script you're mentioning.

this sentence is not required. removed it accordingly.

adgubrud · 2026-06-29T23:28:08Z

+
+<details>
+<summary> Debug Details </summary>
+


Are there common pitfalls you expect the user to run into? What will these useful commands help with?

no. it is just an optional section for further debugging purpose. in general, users don't need to run it themselves.

Okay - what about a few word description of what info each command will provide? See below

adgubrud · 2026-06-30T20:04:10Z

+| **PCT capacity** | Count `bucket-0` once per package/socket |
+| **HP CPU placement** | Dispatch the package-level PCT core budget across the package's PCT reporting powerdomain anchors |
+
+For Intel® Xeon® 6776P system with 2 sockets and 64 cores per socket, `bucket-0` reports using check_pct_status.sh in [check-pct-status session](#2-check-pct-status):


I think it would be helpful to rephrase like this:

Suggested change

For Intel® Xeon® 6776P system with 2 sockets and 64 cores per socket, `bucket-0` reports using check_pct_status.sh in [check-pct-status session](#2-check-pct-status):

The excerpts below are from execution of (check_pct_status.sh](./check_pct_status.sh) on an Intel® Xeon® 6776P system with 2 sockets and 64 cores per socket. Subsequent sections explain the outputs and how to interpret them.

adgubrud · 2026-06-30T20:24:26Z

+```bash
+intel-speed-select --info
+intel-speed-select turbo-freq info -l 1
+intel-speed-select core-power info
+intel-speed-select -c 0 core-power get-assoc
+```


Suggested change

```bash

intel-speed-select --info

intel-speed-select turbo-freq info -l 1

intel-speed-select core-power info

intel-speed-select -c 0 core-power get-assoc

```

```bash

intel-speed-select --info # what info will this give?

intel-speed-select turbo-freq info -l 1 # what info will this give?

intel-speed-select core-power info # what info will this give?

intel-speed-select -c 0 core-power get-assoc # what info will this give

adgubrud · 2026-06-30T20:51:26Z

Please add an entry to the Optimization Zone main README under the Hardware section: https://github.com/intel-ai-tce/optimization-zone/tree/pct#table-of-contents

First Version of Intel PCT BKMs

ec78429

Signed-off-by: louie-tsai <louie.tsai@intel.com>

louie-tsai force-pushed the pct branch from a3812c1 to ec78429 Compare June 23, 2026 20:39

louie-tsai added 2 commits June 23, 2026 13:43

Enhance README with frequency diagram and PCT details

b3637b7

Added a frequency diagram for Xeon 6776P with PCT on and updated the PCT validation instructions.

simplify README.md by foldable items

fb56cf9

rsiyer-intel requested a review from adgubrud June 25, 2026 01:10

rsiyer-intel reviewed Jun 25, 2026

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rsiyer-intel requested changes Jun 26, 2026

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adgubrud requested changes Jun 29, 2026

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louie-tsai requested review from adgubrud and rsiyer-intel June 30, 2026 08:52

Update README.md according to feedback

b5e5dd4

louie-tsai force-pushed the pct branch from b4e8552 to b5e5dd4 Compare June 30, 2026 08:55

adgubrud reviewed Jun 30, 2026

View reviewed changes


		## Overview

		Intel® Priority Core Turbo (PCT) is part of Intel® Speed Select Technology – Turbo Frequency (SST-TF).


		### PCT bucket-count interpretation

		`intel-speed-select turbo-freq info -l <level>` may print the same `bucket-0`,


		But the `turbo-freq` output shows two reporting anchors per package:

		```text

	For Intel® Xeon® 6776P system with 2 sockets and 64 cores per socket, `bucket-0` reports using check_pct_status.sh in [check-pct-status session](#2-check-pct-status):
	The excerpts below are from execution of (check_pct_status.sh](./check_pct_status.sh) on an Intel® Xeon® 6776P system with 2 sockets and 64 cores per socket. Subsequent sections explain the outputs and how to interpret them.

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louie-tsai commented Jun 23, 2026 •

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