[Qemu-devel] [PATCH v9 0/7] trace: Optimize per-vCPU TCG tracing states

[Emilio G. Cota]

v8: https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg02335.html

Changes from v8:

- Rebased on top of the current tracing tree -- the one that includes
  Lluis' fix (2c321e3c486).
- Added Lluis' R-b tag.
- Added perf numbers in the commit log of the last patch (tl;dr: no overhead).

Thanks,

                Emilio

PS. How to quickly get some linux-user perf numbers:

I used dbt-bench[1] for a before/after comparison. I added a script to that
repo (breakdown.pl, see below) to make it play well with barchart[2].
Obtaining a comparison bar chart is quite simple:

1. Generate one dbt-bench output file per QEMU checkout, e.g.:
  $ git checkout orig && make
  [ orig == "before"; new == "after" ]
  $ ./dbt-bench.pl /path/to/qemu/build/qemu-x86_64 > orig.out
  [ then do the same with orig-disabled, new, etc.]
  [...]
  $ ls *.out
  new-disabled.out  new.out  orig-enabled.out  orig.out

2. Call dbt-bench's breakdown.pl script with the --barchart option, then
  pipe the output to barchart, and finally pipe to gnuplot:
  $ ./breakdown.pl --barchart orig.out orig-enabled.out new.out 
new-disabled.out \
    | ../barchart/barchart.pl --extra-gnuplot='set term dumb 140 30' \
         --extra-gnuplot='set title "NBench score; higher is better"' \
    | gnuplot

Note that barchart is just a front-end for gnuplot >=5, so any valid term will
work (e.g. 'set term pngcairo size 1200,500').

[1] https://github.com/cota/dbt-bench
[2] https://github.com/cota/barchart