Snort mailing list archives
Re: Optimized implementation of AC and AC_Q pattern matching algorithms
From: Pablo Cantos <pablocantos () gmail com>
Date: Sat, 26 Jan 2013 16:50:37 +0100
Hi Abed, First of all, thanks for your contribution. I have checked your proposal in snort 2.9.1 by using two different pcap files, one of them (612MB-sized) throws around 900k alerts and the other one (1GB-sized) throws just 55 alerts. I have used an AMD Turion II dual-core mobile M520 at 2.3GHz, 512KB cache L2 by each core and 4GB RAM. These are the performance jumps that I have obtained: 612MB file -> 4.24% for MPSE, 5.93% for ac-q 1GB file -> 7.93% for MPSE, 8.03% for ac-q These results were obtained by measuring the times taken to analyze each pcap file by the MPSE and AC, separately. I have been working for several months with Snort to get improvements in other areas of the MPSE, I have also studied the AC_SEARCH macros and I didn't find them completely efficients but I didn't go further. Now, after seeing your proposal and checking the AC_SEARCH_Q again I thought that taking small changes it could work even better. You have suggested to pre-fetch the new state before was used it: #define AC_SEARCH_Q \ + *acstate_t new_state;* \ for (; T < Tend; T++) \ { \ ps = NextState[state]; \ sindex = xlatcase[T[0]]; \ + *new_state = ps[2 + sindex];* \ if (ps[1]) \ { \ if (MatchList[state]) \ { \ if (_add_queue(&acsm->q,MatchList[state])) \ { \ if (_process_queue(&acsm->q, Match,data)) \ { \ *current_state = state; \ return 1; \ } \ } \ } \ } \ *- state = ps[2 + sindex]; \ * + *state = new_state;* \ } #endif But I think the routine could be more efficient too if we just fetch the new state in the end, and we move down one line: #define AC_SEARCH_Q \ for (; T < Tend; T++) \ { \ ps = NextState[state]; \ *- sindex = xlatcase[T[0]]; \* if (ps[1]) \ { \ if (MatchList[state]) \ { \ if (_add_queue(&acsm->q,MatchList[state])) \ { \ if (_process_queue(&acsm->q, Match,data)) \ { \ *current_state = state; \ return 1; \ } \ } \ } \ } \ *+ sindex = xlatcase[T[0]]; \* state = ps[2 + sindex]; \ } #endif In this way, I think the number of instructions could be reduced too. And these are the results that I have obtained: 612MB file -> 15.66% for MPSE, 22.13% for ac-q 1GB file -> 34.49% for MPSE, 35.13% for ac-q I will try to repeat these tests using other more powerful computers. In any case, we will give more information on Monday.
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Current thread:
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms Pablo Cantos (Jan 26)
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms Joel Esler (Jan 26)
- <Possible follow-ups>
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms abed mohammad kamaluddin (Jan 26)
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms abed mohammad kamaluddin (Jan 28)
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms Pablo Cantos (Jan 28)
- SNORT compilation in ECLIPSE patricio (Jan 28)
- Re: Optimized implementation of AC and AC_Q pattern matching algorithms abed mohammad kamaluddin (Jan 28)