On Fri, May 27, 2022 at 07:09:59PM +0800, Zhang Yuchen wrote:

Add /proc/syscalls to display percpu syscall count.

We need a less resource-intensive way to count syscall per cpu
for system problem location.

There is a similar utility syscount in the BCC project, but syscount
has a high performance cost.

The following is a comparison on the same machine, using UnixBench
System Call Overhead:

    ┏━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━┳━━━━━━━━┓
    ┃ Change        ┃ Unixbench Score ┃ Loss   ┃
    ┡━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━╇━━━━━━━━┩
    │ no change     │ 1072.6          │ ---    │
    │ syscall count │ 982.5           │ 8.40%  │
    │ bpf syscount  │ 614.2           │ 42.74% │
    └───────────────┴─────────────────┴────────┘

UnixBench System Call Use sys_gettid to test, this system call only reads
one variable, so the performance penalty seems large. When tested with
fork, the test scores were almost the same.

So the conclusion is that it does not have a significant impact on system
call performance.

This function depends on CONFIG_FTRACE_SYSCALLS because the system call
number is stored in syscall_metadata.

Death by a thousand cuts. 99% of people won't ever use this.

NAK