Re: [Crash-utility] [PATCH] Fix machdep->HZ calculation for kernel versions > 2.6.0
Hi Bhupesh,
-----Original Message-----
We have hard-coded the HZ value for some ARCHs to either 1000 or 100
(mainly for kernel versions > 2.6.0), which causes 'help -m' to show
an incorrect hz value for various architectures.
Good catch. but seems crash uses (cfq_slice_async * 25) for machdep->hz
if it exists (please see task_init()), RHEL7 has it, but RHEL8 does not.
What do you see on RHEL8 for x86_64 with your patch?
We should search for an alternate way like the current one first.
Thanks,
Kazu
I tested this on ppc64le and x86_64 and the hz value reported is 1000,
whereas the kernel CONFIG_HZ_100 is set to Y. See some logs below:
crash> help -m
flags: 124000f5
(KSYMS_START|MACHDEP_BT_TEXT|VM_4_LEVEL|VMEMMAP|VMEMMAP_AWARE|PHYS_ENTRY_L4|SWAP_ENTRY_L4|RADIX_MMU|OP
AL_FW)
kvbase: c000000000000000
identity_map_base: c000000000000000
pagesize: 65536
pageshift: 16
pagemask: ffffffffffff0000
pageoffset: ffff
stacksize: 16384
hz: 1000
mhz: 2800
[host@rhel7]$ grep CONFIG_HZ_100= redhat/configs/kernel-3.10.0-ppc64le.config
CONFIG_HZ_100=y
Fix the same by using the sysconf(_SC_CLK_TCK) value instead of the
hardcoded HZ values depending on kernel versions.