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[Bug target/85216] Performance issue with PHP on ppc64 systems
- From: "wschmidt at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Thu, 05 Apr 2018 13:04:08 +0000
- Subject: [Bug target/85216] Performance issue with PHP on ppc64 systems
- Auto-submitted: auto-generated
- References: <bug-85216-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85216
--- Comment #9 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
You mentioned you're on a POWER9 machine. It could be that you have firmware
with Spectre mitigations applied, which will affect all indirect branches. It
may be that you do not have Spectre mitigations applied on your x86 machine, in
which case the comparison would be expected to be quite different. Depending
on firmware levels, the mitigations may be able to be switched off, so you
should check into that first. PHP is known to be sensitive to indirect branch
performance.
The Power landing page for these mitigations is
https://www.ibm.com/blogs/psirt/potential-impact-processors-power-family/.
>From here you should be able to get to further information for your specific
hardware and OS version.