Overclocking in linux_ kernel 3.19 + kaveri + iommu – anandtech forums reinstall linux kernel

Overclocking in linux_ kernel 3.19 + kaveri + iommu – anandtech forums reinstall linux kernel tl;dr version: Using kernel 3.19 + hardware IOMMU support on a 7700k resulted in non-HSA software performance regressing to that of the processor @ 3.4 ghz no matter what the clockspeed set in the UEFI. HSA relies on a lot of driver crap to work. Linux kernel development robert love If there is any one thing making it hard to set up and run HSA code on a Kaveri machine today, it has to be the massive amount of software infrastructure that must be laid down on top of the OS in order for HSA to be functional. Latest linux kernel For example, here’s a how-to guide on supporting C++AMP in a Linux environment: https://bitbucket.

org/multicoreware/cppamp-driver-ng/wiki/HSA


Support Status I do not know if that is up-to-date, but that probably was at least true sometime in 2014, if not now. Linux kernel statistics Similar guides intended to help the end-user set up Aparapi for HSA via Java lambdas is slightly less hellacious. One of the major components of the HSA software stack as it currently exists is the Kernel Fusion Driver (or kfd). Install kernel linux Check out slide 24 of this presentation: http://www.slideshare.

net/dibyendu.das/guide-to-heterogeneous-system-architecture-hsa-29621342 In Linux, a kfd is provided in certain versions of the Linux kernal. Linux kernel programming tutorial Up until kernel 3.18, you had to go and get a kernel specially-compiled with kfd support, probably from github.

Linux kernel developer In 3.19, the kfd comes standard for those with supported hardware (it does nothing on a non-Kaveri machine). Linux kernel programming for beginners Those of you who have tried 3.19 on a Kaveri machine may notice the OS griping about IOMMU being disabled and failing to initialize the kfd device or whatever. Linux kernel development pdf Presumably, if your motherboard has proper support for IOMMU, you have it disabled (I did). How big is the linux kernel So I enabled it just to stop the noise. Linux kernel headers download I haven’t even tried any kind of HSA development yet, but hey, may as well reduce the startup error train.

What I did not expect was the weird interaction between a Linux kfd kernel, hardware IOMMU support, and an overclocked CPU. I noticed odd behavior from y-cruncher and some other programs after enabling IOMMU under kernel 3.19. Linux view kernel version It became very slow. How to check linux kernel version Here’s a breakdown of what I recorded when running y-cruncher 512m : (all tests were run at NB 2100mhz, 16gb DDR3-2400, 384 shader iGPU 1028mhz on an Asus A88x-Pro. Get linux kernel The graphics driver is the generic Radeon driver, since fglrx is broken in 3.19) Note that the times here did vary somewhat (I did multiple runs).

Latest stable linux kernel Runs that are listed as identical above were within +/- %3 of each other. Upgrade linux kernel For example, some of the 330s runs were in the range of 336-338s. Linux kernel development 3rd edition pdf I was very careful to make sure that all cores were running at the intended clockspeed. Linux kernel development 3rd edition Not only did I use cpufreq to lock the CPU at maximum frequency all of the time, but I monitored current clockspeed using a Conky widget, and I used cpufreq-info to look at frequency history for the present boot.

Vanilla linux kernel At no point did I observe any throttling of the processor. As a brief test, I booted to Win10 @ 4.5 ghz with the other above settings and IOMMU enabled in the UEFI and ran y-cruncher there, and got in the high 220s which is about what I expect from Win10 (it runs y-cruncher slower than Linux on this box). The implications of this “issue” are not especially positive. View kernel version linux Assuming the HSA software stack is streamlined to the point that it is all integrated into the OS and/or graphics drivers, Kaveri users will have a choice: activate hardware IOMMU support and render CPU overclocking completely inoperable, or disable hardware IOMMU support and break HSA compliance (making HSA-capable software not work).

How to know linux kernel version The issue presently seems to be that creating a kfd device requires the CPU to stay within spec or something. Kernel linux android It is possible that it’s a software issue that can be ironed out in the future . . . Linux kernel programming language if anyone really cares to do so. Okay, another update on this (relatively minor) issue.

Linux kernel programming I still consider it to be of some interest, at least personally, since I am -> <- this close to finally writing some admittedly-primitive HSA software. Linux kernel contribution But I digress. I set the CPU multiplier to Auto and left on all the power management stuff to allow Turbo to function (if it can function at all), and then on top of that, I overclocked the bclk to 119 mhz. Linux kernel changelog This set my base clock at 4016 mhz (p3 state), though under Linux, it still registers as 3.4 ghz. How linux kernel works I can't tell what P0-P2 are right now since the tools to do that under Linux don't seem to work with kernel 3.19 yet. Git linux kernel Oh well. Anyway, I ran y-cruncher 512m and got a score of ~270s with hardware IOMMU enabled (allowing a functional kfd device). Linux kernel source code online Then I disabled hardware IOMMU and got ~240s running the same benchmark using the same configuration. Compilare kernel linux I am guessing that some kind of turbo setting kicked in, hence the superior performance. What this tells me is that initializing a kernel fusion device under 3.19 somehow locks the CPU into the base multiplier for the CPU, overriding UEFI and turbo settings. Lts linux kernel Overclocking the bclk still allows one to OC the chip in these circumstances. So, basically, if you want to overclock Kaveri while doing HSA anything, it's gotta be the bclk. edit: I would like to issue a correction. Download linux kernel source It appears that turbo is *not* happening with 119 bclk and the CPU multiplier set to Auto (resulting in a p3 multi of 34x). Which linux kernel It's just that with IOMMU enabled, there's some kind of a performance penalty. Linux kernel release history I tried 119 bclk and fixed 34x CPU multi (turbo disabled) without IOMMU and got ~240s. Instalar kernel linux With IOMMU enabled, 119 bclk, and fixed 34x multi (again turbo disabled) I got up in the 270s range again. Linux kernel programming language This kind of performance regression is not consistent with any of the other kind of Kaveri throttling I've seen to date. Linux kernel preemption It's a little weird. Gah, I am defeated. Linux kernel lts For whatever reason, using the bclk to increase CPU performance while a kfd device is operating under Linux 3.19 now seems to not want to work anymore. What is the kernel in linux Grumble grumble. Linux kernel mailing list At least overclocking the iGPU and NB still work under those circumstances. Linux kernel jobs I'm not sure why it worked one time and won't work now but the whole thing is a bit odd. Gah, I am defeated. Download linux kernel source code For whatever reason, using the bclk to increase CPU performance while a kfd device is operating under Linux 3.19 now seems to not want to work anymore. How to see kernel version in linux Grumble grumble. O que e kernel linux At least overclocking the iGPU and NB still work under those circumstances. Get linux kernel version I'm not sure why it worked one time and won't work now but the whole thing is a bit odd. C'est la vie. Linux kernel pdf Sometimes it wants to work and sometimes it does not. Linux kernel community I'm still struggling to understand how the chip manages to slow down under these conditions. Ide for linux kernel development It does not help that Java 8 update 40 seems to have killed Math.round() and Math.sqrt() performance which had me really confused for awhile there, thinking my chip was slowing down just on those specific Math library methods (?!?!). Site: https://forums.anandtech.com/threads/overclocking-in-linux-kernel-3-19-kaveri-iommu.2421540/

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