18 November

17 November

The Spectre/Meltdown Performance Impact On Linux 4.20, Decimating Benchmarks With New STIBP Overhead

As outlined yesterday, significant slowdowns with the Linux 4.20 kernel turned out to be due to the addition of the kernel-side bits for STIBP (Single Thread Indirect Branch Predictors) for cross-HyperThread Spectre Variant Two mitigation. This has incurred significant performance penalties with the STIBP support in its current state with Linux 4.20 Git and is enabled by default at least for Intel systems with up-to-date microcode. Here are some follow-up benchmarks looking at the performance hit with the Linux 4.20 development kernel as well as the overall Spectre and Meltdown mitigation impact on this latest version of the Linux kernel.

17 November 12:39 PM EST - Software - 55 Comments
AMD Optimizing C/C++ Compiler 1.3 Brings More Zen Tuning

Earlier this month AMD quietly released a new version of their Optimizing C/C++ compiler in the form of AOCC 1.3. This new compiler release has more Zen tuning to try to squeeze even more performance out of Ryzen/EPYC systems when using their LLVM-based compiler.

17 November 06:27 AM EST - AMD - AOCC 1.3 - 2 Comments
Radeon GCC Back-End Updated For Running Single-Threaded C & Fortran On AMD GPUs

Back in September Code Sourcery / Mentor Graphics posted the Radeon GCC back-end they have been developing with the cooperation of AMD. This is for allowing the GCC compiler to eventually offload nicely to Radeon GPUs with its different programming languages and supported parallel programming models, particularly with OpenMP and OpenACC in mind. But for now this patch series just works with single-threaded C and Fortran programs. The second version of this port was posted for review.

17 November 05:20 AM EST - GNU - Radeon GCC v2 - 2 Comments

16 November

The Open-Source AMD Linux Driver Stack Hitting Problems With The Radeon RX 590

While the Radeon RX 590 that launched this week is just yet another Polaris refresh, it turns out the open-source AMD Linux graphics driver stack isn't yet playing well with retail RX 590 graphics cards. This is quite a surprise considering the PCI ID was picked up months ago and the mature Polaris Linux driver support for quite a while now, but could be like the rough Raven Ridge Linux experience where the production cards with the shipping vBIOS isn't what the developers encountered during their pre-production driver enablement.

16 November 08:00 PM EST - Radeon - Radeon RX 590 + Linux - 40 Comments
More Benchmarks Of The Performance Pullback In Linux 4.20

Last night I published some benchmarks after finding Linux 4.20 is regressing in several workloads compared to Linux 4.18/4.19 and at least was affecting Intel Core i9 "HEDT" boxes. Here are more affected workloads regressing on Linux 4.20 and it's not just limited to high-end hardware.

16 November 06:54 AM EST - Linux Kernel - Linux 4.20 Performance Drop - 13 Comments

15 November

Benchmarking Packet.com's Bare Metal Intel Xeon / AMD EPYC Cloud

With the tests earlier this week of the 16-way AMD EPYC cloud comparison the real standout of those tests across Amazon EC2, Packet, and SkySilk was Packet's bare metal cloud. For just $1.00 USD per hour it's possible to have bare metal access to an AMD EPYC 7401P 24-core / 48-thread server that offers incredible value compared to the other public cloud options for on-demand pricing. That led me to running some more benchmarks of Packet.com's other bare metal cloud options to see how the Intel Xeon and AMD EPYC options compare.

15 November 07:40 AM EST - Computers - 1 Comment
The Newest Mesa NIR/SPIR-V Code For Handling OpenCL Kernels

It's now been nearly one year since longtime Nouveau contributor Karol Herbst joined Red Hat where one of his big projects has been working on OpenCL support for this open-source NVIDIA driver by bringing up NIR/SPIR-V support and making the necessary improvements for allowing OpenCL kernels to be represented in that IR commonly used by the Mesa drivers. The work still isn't yet in Mesa Git, but Karol this week sent out his newest patches.

15 November 05:46 AM EST - Mesa - OpenCL NIR - 5 Comments
PHP Lands Preload Feature, Boosting Performance In Some Cases 30~50%

PHP developers unanimously approved and already merged support for the new "preloading" concept for this web server language. PHP preloading basically allows loading PHP code that persists as long as the web server is running and that code will always be ready for each subsequent web request, which in some cases will dramatically speed-up the PHP performance on web servers.

15 November 05:35 AM EST - Free Software - PHP Preload - 5 Comments

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