[ThinLTO] Correct documentation on default number of threads

Summary:
The number of threads used for ThinLTO backend parallelism was
dropped to the number of cores in r284618 to avoid oversubscribing
physical cores due to hyperthreading. This updates the documentation
to reflect that change.

Fixes PR38610.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D50882

llvm-svn: 340021
This commit is contained in:
Teresa Johnson 2018-08-17 13:19:36 +00:00
parent 16a2f54eee
commit c9818ebc02

View File

@ -105,7 +105,9 @@ Controlling Backend Parallelism
-------------------------------
.. _parallelism:
By default, the ThinLTO link step will launch up to
By default, the ThinLTO link step will launch as many
threads in parallel as there are cores. If the number of
cores can't be computed for the architecture, then it will launch
``std::thread::hardware_concurrency`` number of threads in parallel.
For machines with hyper-threading, this is the total number of
virtual cores. For some applications and machine configurations this