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> maxcpus=5
mithrandir
post Mar 21 2019, 03:06 PM
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Today, just out of interest I had a look at the kernel cmdline and noticed we are are restricted to 5 cpus:

root@gemini:/home/gemini# cat /proc/cmdline
console=tty0 console=ttyMT0,921600n1 root=/dev/ram vmalloc=496M slub_max_order=0 slub_debug=OFZPU androidboot.hardware=mt6797 maxcpus=5 androidboot.verifiedbootstate=green bootopt=64S3,32N2,64N2 log_buf_len=4M printk.disable_uart=1 bootprof.pl_t=1127 bootprof.lk_t=2950 boot_reason=4 androidboot.serialno=TGRWNRQ8ORQKC6TK androidboot.bootreason=wdt_by_pass_pwk gpt=1 usb2jtag_mode=0

To prove this I tried while running sysbench ( sysbench --test=threads --num-threads=99 run ) to see the count of enabled cpus:
root@gemini:/home/gemini# cat /proc/cpuinfo |grep proc|wc -l
5

The count of active cpus never went above 5 (as expected). Does anybody know the reason for this restriction? Has anybody already tried to increase this number, maybe to 10? Do we all have this restriction(might be a problem with my setup, but don't think so)? Where could this be changed (it is not part of the mkbootimg call)?

Mith
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Eric BF
post Mar 22 2019, 12:37 AM
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QUOTE(mithrandir @ Mar 21 2019, 11:06 PM) *
Do we all have this restriction(might be a problem with my setup, but don't think so)?

I don't know but I can confirm that I also see maxcpus=5 in the output of that command.
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Adam Boardman
post Mar 22 2019, 01:04 AM
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I assumed it was related to the big.little ARM thing were we want to either be running the higher or lower powered cores. If anyone is running the latest android release (I'm still a few behind as I never use it), it would be very interesting to compare the Android side cmdline and kernel build parameters (probably extract-able from /proc/config.gz).

I was planning on checking this after they release the 8.1, but if anyone wants to do so sooner then there could still be interesting things to learn from the last release.
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Kiriririn
post Mar 22 2019, 03:43 AM
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This definitely did work in the past, i.e. running a heavy multi threaded process fired up all 10 CPU cores
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Varti
post Mar 22 2019, 04:38 AM
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QUOTE(Adam Boardman @ Mar 22 2019, 10:04 AM) *
If anyone is running the latest android release (I'm still a few behind as I never use it), it would be very interesting to compare the Android side cmdline and kernel build parameters (probably extract-able from /proc/config.gz).

I'm running the latest Android release, I have checked under Termux though I couldn't find neither /proc/config.gz nor the /boot folder itself. I guess this might be retrieved from the kernel sources (https://github.com/dguidipc/gemini-android-kernel-3.18/tree/master/kernel-3.18/arch/arm/configs), though I believe there's no guarantee that the config file there was the one used for the latest compiled kernel.

Varti
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mithrandir
post Mar 22 2019, 09:23 AM
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QUOTE(Varti @ Mar 22 2019, 04:38 AM) *
I'm running the latest Android release, I have checked under Termux though I couldn't find neither /proc/config.gz nor the /boot folder itself. I guess this might be retrieved from the kernel sources (https://github.com/dguidipc/gemini-android-kernel-3.18/tree/master/kernel-3.18/arch/arm/configs), though I believe there's no guarantee that the config file there was the one used for the latest compiled kernel.

Varti


It is not related to kernel configuration. From kernel config:
CONFIG_NR_CPUS=10
CONFIG_CMDLINE="console=tty0 console=ttyMT3,921600n1 root=/dev/ram vmalloc=496M slub_max_order=0 slub_debug=O "

Mith
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