News: 0001493278

  ARM Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life (Terry Pratchett, Jingo)

Intel TPEBS & LBR Event Logging Supported By Linux 6.12 With Perf Tools

([Linux Kernel] 3 Hours Ago Intel PEBS + LBR Event Logging)


The perf tooling changes were merged today for the in-development [1]Linux 6.12 kernel. Notable on the perf tools side is supporting some features found in newer Intel processors.

The perf tools with Linux 6.12 add Intel branch counters support using LBR event logging. The Last Branch Record (LBR) event logging allows for logging PMU event data within LBRs.

This LBR Event Logging support is first found with Intel Xeon 6 "Sierra Forest" and upcoming Grand Ridge processors. Grand Ridge and Sierra Forest feature Crestmont E cores but over the incarnation found within Meteor Lake there is now this PMU LBR event logging capability. The Intel documentation with the patches goes on to explain of the LBR event logging:

"The LBR event logging introduces a per-counter indication of precise event occurrences in LBRs. It can provide a means to attribute exposed retirement latency to combinations of events across a block of instructions. It also provides a means of attributing Timed LBR latencies to events."

The other new Intel CPU feature with the perf tools work for Linux 6.12 is supporting Timed PEBS, or Precision Event-Based Sampling. With the perf stat command the new "--enable-tpebs-recording" option can be used for enabling Timed PEBS (TPEBS). More details on Timed PEBS as found with Meteor Lake and Granite Rapids can be found via [2]this Intel.com documentation .

Also on the Intel side with Linux 6.12 perf tools is updating the Meteor Lake metric JSON files for perf events.

Linux 6.12 per tools also allows using BPF+BTF to collect and print syscall and tracepoint arguments within "perf trace", various data type profiling improvements, and more. See [3]the Git merge for the full list of perf tools feature changes this cycle.



[1] https://www.phoronix.com/search/Linux+6.12

[2] https://www.intel.com/content/www/us/en/developer/articles/technical/timed-process-event-based-sampling-tpebs.html

[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=891e8abed532423d3b918b0c445dc8919bc445b5


phoronix

Gentlemen,
Whilst marching from Portugal to a position which commands the
approach to Madrid and the French forces, my officers have been
diligently complying with your requests which have been sent by H.M. ship
from London to Lisbon and thence by dispatch to our headquarters.
We have enumerated our saddles, bridles, tents and tent poles,
and all manner of sundry items for which His Majesty's Government holds
me accountable. I have dispatched reports on the character, wit, and
spleen of every officer. Each item and every farthing has been accounted
for, with two regrettable exceptions for which I beg your indulgence.
Unfortunately the sum of one shilling and ninepence remains
unaccounted for in one infantry battalion's petty cash and there has been
a hideous confusion as the number of jars of raspberry jam issued to
one cavalry regiment during a sandstorm in western Spain. This
reprehensible carelessness may be related to the pressure of circumstance,
since we are war with France, a fact which may come as a bit of a surprise
to you gentlemen in Whitehall.
This brings me to my present purpose, which is to request
elucidation of my instructions from His Majesty's Government so that I
may better understand why I am dragging an army over these barren plains.
I construe that perforce it must be one of two alternative duties, as
given below. I shall pursue either one with the best of my ability, but
I cannot do both:
1. To train an army of uniformed British clerks in Spain for the
benefit of the accountants and copy-boys in London or perchance:
2. To see to it that the forces of Napoleon are driven out of Spain.
-- Duke of Wellington, to the British Foreign Office,
London, 1812