Re: [PATCH] locking/lockdep: Increase MAX_LOCKDEP_ENTRIES by half

From: Qian Cai
Date: Tue May 26 2020 - 16:17:50 EST


On Tue, May 26, 2020 at 09:56:30PM +0200, Peter Zijlstra wrote:
> On Tue, May 26, 2020 at 02:58:50PM -0400, Qian Cai wrote:
>
> > I still don't understand why reading all sysfs files on this system
> > could increase that much, but here is the lockdep file after
> > running sysfs read to see if you could spot anything obviously,
> >
> > https://cailca.github.io/files/lockdep.txt
>
> 00000000f011a2a5 OPS: 20 FD: 45 BD: 1 .+.+: kn->active#834
>
> is that somewhere near the number of CPUs you have?

834? No.

# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 128
On-line CPU(s) list: 0-127
Thread(s) per core: 2
Core(s) per socket: 32
Socket(s): 2
NUMA node(s): 8
Vendor ID: AuthenticAMD
CPU family: 23
Model: 1
Model name: AMD EPYC 7601 32-Core Processor
Stepping: 2
CPU MHz: 2932.801
CPU max MHz: 2200.0000
CPU min MHz: 1200.0000
BogoMIPS: 4391.87
Virtualization: AMD-V
L1d cache: 32K
L1i cache: 64K
L2 cache: 512K
L3 cache: 8192K
NUMA node0 CPU(s): 0-7,64-71
NUMA node1 CPU(s): 8-15,72-79
NUMA node2 CPU(s): 16-23,80-87
NUMA node3 CPU(s): 24-31,88-95
NUMA node4 CPU(s): 32-39,96-103
NUMA node5 CPU(s): 40-47,104-111
NUMA node6 CPU(s): 48-55,112-119
NUMA node7 CPU(s): 56-63,120-127

>
> Anyway, there's very long "kn->active#..." chains in there, which seems
> to suggest some annotation is all sorts of buggered.