Re: Linux audit performance impact

[Steve Grubb <sgrubb@redhat.com>]

Hello,

On Wednesday, January 28, 2015 02:57:58 PM Viswanath, Logeswari P wrote:
> We want to know audit performance impact on RHEL and Suse linux to help us
> evaluate linux audit as data source for our host based IDS. When we ran our
> own performance test with a test audispd plugin, we found if a system can
> perform 200000 open/close system calls per second without auditing, system
> can perform only 3000 open/close system calls auditing is enabled for
> open/close system call which is a HUGE impact on the system performance. It
> would be great if anyone can help us answering the following questions.
> 
> 
> 1)      Is this performance impact expected? If yes, what is the reason
> behind it and can we fix it?

I'll leave this for the kernel guys to answer. That said, I think more 
detailed information might be helpful.

If auditd is not started and events go to syslog, does the performance change? 
To do this audit=1 on boot line and auditctl -R /etc/rules.d/your.rules

what rules do you have loaded?

What do you get when audit is enabled and no rules loaded?

If you have other syscall rules loaded that are not open and openat or close, 
does the performance change? I suspect that if you trigger a rule, you are 
thrown onto the slow path. Open is perhaps the most lengthy because of 
multiple auxiliary records and path resolution. But we need data to tell.

That said, I know that the kernel audit path changed a couple years ago so it 
might be worthwhile to test against an old kernel to see if the change has 
affected performance.

-Steve

> 2)      Have anyone done any benchmarking for performance impact? If yes,
> can you please share the numbers and also the steps/programs used the run
> the same.
> 
> 3)      Help us validating the performance test we have done in our test
> setup using the steps mentioned along with the results attached.
> 
> Attached test program (loader.c) to invoke open and close system calls.
> Attached idskerndsp is the audispd plugin program.
> We used time command to determine how much time the system took to complete
> 50000 open/close system calls without (results attached Without-auditing)
> and with auditing enabled on the system (With-auditing-NOLOG-audispd-plugin
> and With-auditing-RAW)
> 
> System details:
> 
> 1 CPU machine
> 
> OS Version
> RHEL 6.5
> 
> Kernel Version
> uname -r
> 2.6.32-431.el6.x86_64
> 
> Note: auditd was occupying 35% of CPU and was sleeping for most of the time
> whereas kauditd was occupying 20% of the CPU.
> 
> Thanks & Regards,
> Logeswari.