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Oprofileによるボトルネックの調査 メモ

Last updated at Posted at 2015-10-21

インストール

$ yum install oprofile

使い方

$ opcontrol --reset  #プロファイル結果をクリア
$ opcontrol --start  #プロファイル開始
$ opcontrol --stop   #プロファイル終了

結果の確認

$ opreport   # システム全体ののプロファイル結果
$ opreport -l /home/trae/bin/traepktd    #指定プログラムのプロファイル結果(サマリ)
$ opannotate -a /home/trae/bin/traepktd    #指定プログラムのプロファイル結果(詳細)

下記の例だと、"hl_xxxxx"がかなりのボトルネックになっている。
"hl_xxxxx"に性能改善対策がうてれば、実行速度の向上が見込める。

CPU: Intel Architectural Perfmon, speed 3466.91 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
samples  %        symbol name
1384167  11.0792  hl_xxxxx
755803    6.0496  tcp_mxxxxx
723457    5.7907  http_Pxxxxxxx
637085    5.0994  pkt_xxxxxxxx
566604    4.5352  pkt_xxxxxxxx
453462    3.6296  .plt
415683    3.3272  pkt_ipxxxxxxxxxx
396182    3.1711  pkt_ifxxxxxxxxxx
373027    2.9858  pkt_tcpxxxxxxxxx
364275    2.9157  ut_xxxxxxxxx
342519    2.7416  http_xxxxxxxxxxxx
315162    2.5226  ux_xxxxxxxxxxx
~

ソースの該当箇所を確認。
forループの中のmemcmpをどうにかすればよさげなのが判断できる。

/* 
 * Command line: opannotate -s ./xxxxxxxx
 * 
 * Interpretation of command line:
 * Output annotated source file with samples
 * Output all files
 * 
 * CPU: Intel Architectural Perfmon, speed 3466.91 MHz (estimated)
 * Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
 */
/* 
 * Total samples for file : "/home/xxxxxxxx.c"
 * 
 * 910908 16.8646
 */

               :uint64_t hl_xxxxx(hl_t *hl, void *key)

 64052  1.1859 :	for (ridx = __hl_bkt(hl)[hl_hash(key, db->klen, 1981) % db->bnum];
 87402  1.6182 :		ridx > 0;
     2 3.7e-05 :		ridx = *__hl_rec_syn(hl, ridx)) {

273682  5.0670 :		if (memcmp((void *)__hl_rec(hl, ridx), key, db->klen) == 0) {
               :			dprint("key matched at "REC_FMT"\n", REC_ARG(hl, ridx));

               :	}

  3205  0.0593 :}
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