[Snort-devel] Optimized implementation of AC and AC_Q pattern matching algorithms

Hui Cao hcao at ...402...
Fri Jan 25 10:40:40 EST 2013

Hi Abed,

Thanks for the patch. I will create a bug to track this.

What's the compiling option for your testing? How did you profiling
the performance? Knowing those might help us verify the performance


On Fri, Jan 25, 2013 at 9:59 AM, abed mohammad kamaluddin
<abedamu at ...2499...> wrote:
> Hi,
> I have been working on porting snort to multicore MIPs (Octeon) processors
> for high performance networks for which I have analyzed the existing
> software pattern matching algorithms. Even though the focus is on using our
> own proprietary hardware pattern matching engine (which gives more than
> double the performance of the best software algorithm), we are supporting
> all s/w algorithms on our port.
> While profiling Aho-Corasick based search (ac and ac-q) , it was found that
> the number of instructions could be significantly reduced in the main loop
> (the AC_SEARCH macros) if the next state was pre-fetched before it was used.
> Each byte of Input passes through this loop, so the performance increase is
> significant w.r.t to the present implementation. Unexpectedly the gcc
> compiler is unable to perform this optimization on its own.
> Though simple optimization, it translates into more than 10-14% performance
> jump. Also, this is not processor specific. I have tried on both 2U Dual
> Intel Xeon Server and OCTEON68XX (32 core CAVIUM processor) for above 20Gbps
> line rates and I see the bump up. Also the same behavior is observed for
> snort-2.9.0 to snort-2.9.4.
> I am attaching the patch (w.r.t snort 2.9.4) , and would like to contribute
> the same to OSS community.
> Regards
> --
> Abed M K
> Software Engineer
> Cavium IDC
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