Re: [PATCH v2 00/15] Introduce threaded trace streaming for basic perf record operation

Jiri Olsa
2020-10-24T15:43:20Z

On Wed, Oct 21, 2020 at 06:52:43PM +0300, Alexey Budankov wrote:
>
> Changes in v2:
> - explicitly added credit tags to patches 6/15 and 15/15,
> additionally to cites [1], [2]
> - updated description of 3/15 to explicitly mention the reason
> to open data directories in read access mode (e.g. for perf report)
> - implemented fix for compilation error of 2/15
> - explicitly elaborated on found issues to be resolved for
> threaded AUX trace capture
>
> v1: https://lore.kernel.org/lkml/810f3a69-0004-9dff-a911-b7ff97220ae0@linux.intel.com/
>
> Patch set provides threaded trace streaming for base perf record
> operation. Provided streaming mode (--threads) mitigates profiling
> data losses and resolves scalability issues of serial and asynchronous
> (--aio) trace streaming modes on multicore server systems. The patch
> set is based on the prototype [1], [2] and the most closely relates
> to mode 3) "mode that creates thread for every monitored memory map".

so what I liked about the previous code was that you could
configure how the threads would be created

default --threads options created thread for each cpu like
in your change:

$ perf record -v --threads ...
...
thread 0 monitor: 0 allowed: 0
thread 1 monitor: 1 allowed: 1
thread 2 monitor: 2 allowed: 2
thread 3 monitor: 3 allowed: 3
thread 4 monitor: 4 allowed: 4
thread 5 monitor: 5 allowed: 5
thread 6 monitor: 6 allowed: 6
thread 7 monitor: 7 allowed: 7

then numa based:

$ perf record -v --threads=numa ...
...
thread 0 monitor: 0-5,12-17 allowed: 0-5,12-17
thread 1 monitor: 6-11,18-23 allowed: 6-11,18-23

socket based:

$ perf record -v --threads=socket ...
...
thread 0 monitor: 0-7 allowed: 0-7

core based:

$ perf record -v --threads=core ...
...
thread 0 monitor: 0,4 allowed: 0,4
thread 1 monitor: 1,5 allowed: 1,5
thread 2 monitor: 2,6 allowed: 2,6
thread 3 monitor: 3,7 allowed: 3,7

and user configurable:

$ perf record -v --threads=0-3/0:4-7/4 ...
...
threads: 0. monitor 0-3, allowed 0
threads: 1. monitor 4-7, allowed 4

so this way you could easily pin threads to cpu/core/socket/numa,
or to some other cpu of your choice, because this will be always
game of try and check where I'm not getting LOST events and not
creating 1000 threads

perf record: Add support for threads numa option value
perf record: Add support for threads socket option value
perf record: Add support for threads core option value
perf record: Add support for threads user option value

jirka