Evaluate using Profile-Guided Optimization (PGO) and Post-Link Optimization (PLO) on VTS about nginx-module-vts HOT 3 OPEN

@zamazan4ik
I could completely make sense what you suggested, it can be optimized the following approach. But I'm not sure how can be improved it such that process.
https://stackoverflow.com/questions/13881292/what-information-does-gcc-profile-guided-optimization-pgo-collect-and-which-op
We also can find the detail of this mechanisms on this paper.
https://people.freebsd.org/~lstewart/articles/cpumemory.pdf section7.4.

In generally if it could be improve the performance which you expected, we could be written the following a building process as a tips in README instead of providing the optimized binary. Only we prefer to build such the way at users own risks.

compile with fprofile-generate

% pwd
/home/u5surf/nginx
% CC=gcc ./auto/configure --with-cc-opt='-fprofile-generate -fprofile-dir=./objs' --with-ld-opt='-lgcov' --add-module=../nginx-module-vts
% make

test a several cases

% pwd
/home/u5surf/nginx-module-vts
% sudo PATH=/home/u5surf/nginx/objs:$PATH prove -r t/000.display_html.t
...(during runtime it records coverage data into .gcda files)

recompile with fprofile-use

% pwd
/home/u5surf/nginx
% CC=gcc ./auto/configure --with-cc-opt='-fprofile-use -fprofile-dir=../nginx-module-vts/objs' --with-ld-opt='-lgcov' --add-module=../nginx-module-vts
% make

from nginx-module-vts.

@zamazan4ik Thanks interesting suggestion.
I consider that such optimize through this module might be limited. At first this module is a kind of nginx module, in short the build process is just nginx one, that might only the optimization of nginx.
We should suggest such build process to nginx developers instead this module as formally.

from nginx-module-vts.

Excuse me for the so late response - holidays, you know :)

In generally if it could be improve the performance which you expected, we could be written the following a building process as a tips in README instead of providing the optimized binary. Only we prefer to build such the way at users own risks.

I agree with your suggestion. Having such documentation somewhere (like in the README file) is a good thing to the users to have.

I have the following suggestions for your documentation about PGO:

• Clang also supports PGO so there is no need to bind the PGO documentation only to the GCC compiler. PGO with Clang can be enabled with the same -fprofile-generate/-fprofile-use flags.
• It would be great if in the documentation you put information about the actual performance wins with PGO in the VTS module. But for that, we need to perform some benchmarks.

Here I gathered some PGO-related documentation examples:

• ClickHouse: https://clickhouse.com/docs/en/operations/optimizing-performance/profile-guided-optimization
• Databend: https://databend.rs/doc/contributing/pgo
• Vector: https://vector.dev/docs/administration/tuning/pgo/
• Nebula: https://docs.nebula-graph.io/3.5.0/8.service-tuning/enable_autofdo_for_nebulagraph/
• GCC: Official docs, section "Building with profile feedback"
• Clang:
  • https://llvm.org/docs/HowToBuildWithPGO.html
  • https://llvm.org/docs/AdvancedBuilds.html
• Rustc: https://rustc-dev-guide.rust-lang.org/building/optimized-build.html#profile-guided-optimization
• tsv-utils: https://github.com/eBay/tsv-utils/blob/master/docs/BuildingWithLTO.md

from nginx-module-vts.