This bug has been migrated to another issue tracking site. It has been closed here and may no longer be being monitored.

If you would like to get updates for this issue, or to participate in it, you may do so at Red Hat Issue Tracker .
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Bug 2224925 - Build Clang with Profile-Guided Optimization (PGO)
Summary: Build Clang with Profile-Guided Optimization (PGO)
Keywords:
Status: CLOSED MIGRATED
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: clang
Version: CentOS Stream
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Tom Stellard
QA Contact: qe-baseos-tools-bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2023-07-24 00:18 UTC by Alexander Zaitsev
Modified: 2023-09-22 17:07 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2023-09-22 17:07:38 UTC
Type: Story
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker   RHEL-7436 0 None Migrated None 2023-09-22 17:07:33 UTC
Red Hat Issue Tracker RHELPLAN-163022 0 None None None 2023-07-24 00:19:40 UTC

Description Alexander Zaitsev 2023-07-24 00:18:31 UTC 
Description of problem:

Clang supports (https://llvm.org/docs/HowToBuildWithPGO.html) bootstrapping with Profile-Guided Optimization (PGO). It increases Clang performance a lot (+20% according to the official docs and my own tests). The same thing is already enabled for GCC in Fedora (profiledbootstrap option). I think the same thing could be done for Clang since in the current build script I don't see that Clang is built with PGO.

Actual result:
Clang package is not PGO-optimized.

Expected results:
Provided Clang binaries with Fedora are built with PGO.

Additional option:
As an additional option, you could try to build binary with LLVM BOLT (https://github.com/facebookincubator/BOLT/blob/main/bolt/docs/OptimizingClang.md) but I guess it's another question and it's much more complicated topic.

More about PGO-related optimizations for other software you can find here: https://github.com/zamazan4ik/awesome-pgo

More about PGO optimizations for other LLVM-based projects (you can be interested in them too) you can find here: https://github.com/llvm/llvm-project/issues/63486

Also, I created a similar request in other Linux distributions:
- Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=2156679
- Rocky Linux: https://bugs.rockylinux.org/view.php?id=1618
- AlmaLinux: https://bugs.almalinux.org/view.php?id=350
Comment 1 Alexander Zaitsev 2023-09-01 02:09:29 UTC 
By the way, there is an already supported by Clang extra optimization step after PGO - optimizing Clang with LLVM BOLT.

Here you can read the results of optimizing Clang with PGO + LLVM BOLT compared to PGO:
* Slides: https://llvm.org/devmtg/2022-11/slides/Lightning15-OptimizingClangWithBOLTUsingCMake.pdf
* Results on building Clang: https://github.com/ptr1337/llvm-bolt-scripts/blob/master/results.md
* Linaro results: https://android-review.linaro.org/plugins/gitiles/toolchain/llvm_android/+/f36c64eeddf531b7b1a144c40f61d6c9a78eee7a
* on AMD 7950X3D: https://github.com/llvm/llvm-project/issues/65010#issuecomment-1701255347

Related discussion in the upstream: https://github.com/llvm/llvm-project/issues/65010
Comment 2 RHEL Program Management 2023-09-22 17:05:41 UTC 
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.
Comment 3 RHEL Program Management 2023-09-22 17:07:38 UTC 
This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there.

Due to differences in account names between systems, some fields were not replicated.  Be sure to add yourself to Jira issue's "Watchers" field to continue receiving updates and add others to the "Need Info From" field to continue requesting information.

To find the migrated issue, look in the "Links" section for a direct link to the new issue location. The issue key will have an icon of 2 footprints next to it, and begin with "RHEL-" followed by an integer.  You can also find this issue by visiting https://issues.redhat.com/issues/?jql= and searching the "Bugzilla Bug" field for this BZ's number, e.g. a search like:

"Bugzilla Bug" = 1234567

In the event you have trouble locating or viewing this issue, you can file an issue by sending mail to rh-issues. You can also visit https://access.redhat.com/articles/7032570 for general account information.
Note You need to log in before you can comment on or make changes to this bug.