On 10/05/2021 10:48, Richard Purdie wrote: > On Mon, 2021-05-10 at 10:33 +0800, Yu, Mingli wrote: >> From: Mingli Yu <mingli...@windriver.com> >> >> For the jitter entropy source, each task thread will create an internal >> counter timer thread when the system clock resolution is under 5MHz. >> >> But it will introduce high cpu usage for a long time and also make random >> data generate too slow if sets the CPU affinity mask of the internal counter >> timer thread. >> >> There is no solution until now and the Upstream recommends to disable >> the internal timer and think Jitter RNG will not work due to the coarse >> timer. Check [1] and [2] for more details. >> >> So disable the CPU affinity mask as a workaround to avoid lots of context >> switch and too high cpu load for a long time. >> >> [1] https://github.com/smuellerDD/jitterentropy-library/issues/37 >> [2] https://github.com/nhorman/rng-tools/pull/123 >> >> Signed-off-by: Mingli Yu <mingli...@windriver.com> >> --- >> ...tter.c-disable-the-CPU-affinity-mask.patch | 48 +++++++++++++++++++ >> .../rng-tools/rng-tools_6.11.bb | 1 + >> 2 files changed, 49 insertions(+) >> create mode 100644 >> meta/recipes-support/rng-tools/rng-tools/0001-rngd_jitter.c-disable-the-CPU-affinity-mask.patch > > Thanks for investigating this upstream. From an OE-Core perspective, I've very > reluctant to take what looks like a very board specific change which the > upstream > is advising against. The issue is that this will affect all hardware, not just > the hardware which has the issue. I think we need to find a better solution. > > Cheers, > > Richard >
FWIW I forcefully have to ensure nothing pulls in rng-tools in my builds which are for two different Rockchip chipsets (armv7 and armv8) as the rng-tools binary pegs the CPU at 100% for minutes after boot, every boot. It's particularly annoying as openssh brings it in by default which I've unsuccessfully argued is wrong before. I believe the problem is probably fairly widespread but just unnoticed. Regards, -- Jack Mitchell, Consultant https://www.tuxable.co.uk
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