Date: Thu, 24 Jan 2019 18:58:40 +0100 From: Gary Jennejohn <gljennjohn@gmail.com> To: freebsd-hackers@freebsd.org Subject: Re: Scheduled ideas: Two threads with one "stone" Message-ID: <20190124185840.0973ea7f@ernst.home> In-Reply-To: <1ce4898f-942b-d5ec-7563-fdceb56f4e88@rlwinm.de> References: <CACpH0Mc09tjybFKpdh=yMRKxvMuHjRC4k6sen1kUo2AoLd7UHw@mail.gmail.com> <1ce4898f-942b-d5ec-7563-fdceb56f4e88@rlwinm.de>
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On Thu, 24 Jan 2019 18:34:21 +0100 Jan Bramkamp <crest@rlwinm.de> wrote: > On 24.01.19 17:32, Zaphod Beeblebrox wrote: > > W.R.T. hyperthreading, it's come to my attention that FreeBSD has had some > > recommendations for awhile --- namely hyperthreading is bad for secure > > systems. That-is-to-say this is not about recent vulnerabilities of recent > > Intel flavoured CPUs, but rather some thoughts on a different solution to a > > different problem. > > > > I was building world on my laptop when I noticed how sucky it had become. > > Now... I well know this is due to the fact that even a "nice -19 make -j32 > > buildworld" will slow the normal priority userland down by about 1/2 > > because the thread that is "me" on the CPU is competing with one of the > > threads that is saturating the CPU. My normal priority thread will get > > scheduled, but it competes equally for resources with threads at much lower > > priority. > > You can use `idprio 10 ...` to minimize the impact of CPU bound tasks. > If you want to go even further you could apply hierarchical resource > limits on the make process. The idprio chainloader puts make and all its > descendants into the idle scheduling class which allows normal time > sharing threads to preempt them. > Or switch to SCHED_4BSD. I ran your command line and was still able to watch a HD movie in full screen mode without a single glitch. My Ryzen has 6 physical cores and 6 SMTs. -- Gary Jennejohn
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