Month: April 2025

A simple guide of using LinuxKI

I think LinuxKI is an underrated Linux performance tuning tool. When I worked in HPE, one of my colleagues heavily relied on LinuxKI to do performance tuning. I still remember one of his workload is like this: 8 Oracle databases run in 8 docker containers simultaneously, and he did following things every day:
(1) Execute runki to collect data;
(2) Use kiall to analyse data, then tune some parameters;
(3) Go back to step (1).

Below is a simple guide of how to use LinuxKI, and I assume the LinuxKI is already installed:
(1) Collect data in /dev/shm directory to reduced the risk of missing LinuxKI events during the tracing and does not add to the disk workload, but be sure /dev/shm has enough memory:

$ cd /dev/mem

(2) Run runki command (-R options means capturing advanced CPU stats):

$ sudo /opt/linuxki/runki -R

After finishing, there is a compressed *.tgz file:

$ ll -h
total 359M
-rw-r--r--. 1 root root 359M Apr 29 13:39 ki_all.pocket-p2.0429_1337.tgz

(3) Copy the *.tgz file into home directory:

$ cp ki_all.pocket-p2.0429_1337.tgz ~/

and now the original file can be safely removed.

(4) The final step is generating the reports:

$ cd ~
$ /opt/linuxki/kiall -r
Processing files in: /home/nanxiao/pocket-p2/0429_1337
Merging KI binary files.  Please wait...
ki.bin files merged by kiinfo -likimerge
/opt/linuxki/kiinfo -kitrace -ts 0429_1337
/opt/linuxki/kiinfo -kiall csv -html -ts 0429_1337
kiall complete

Then we can check and analyse the reports now.

Test locking a spinlock twice behaviour

I was curious whether pthread_spin_lock() can really detect deadlock scenario, so I wrote a simple program to test:

#include <stdio.h>
#include <pthread.h>

int
main(void)
{
    pthread_spinlock_t lock;
    if (pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE) != 0) {
        perror("pthread_spin_init error");
        return 1;
    }

    if (pthread_spin_lock(&lock) != 0) {
        perror("pthread_spin_lock 1 error");
        return 1;
    }

    if (pthread_spin_lock(&lock) != 0) {
        perror("pthread_spin_lock 2 error");
        return 1;
    }

    return 0;
}

Tested it on both Linux and FreeBSD, the program blocked on the second pthread_spin_lock, never return:

$ ./double_lock

P.S., the code can be found here.