<html><body><div style="font-family: times new roman, new york, times, serif; font-size: 12pt; color: #000000"><div>Hi,</div><div><br></div><div>Is your sched_getcpu() system call a vdso too ? This may explain the difference.<br></div><div><br></div><div>Moreover, make sure you #define _LGPL_SOURCE in your benchmark program<br></div><div>before including any lttng ust header. It will inline many functions associated with<br></div><div>tracepoints.<br></div><div><br></div><div>Then, you can try using "perf" to profile the runtime execution of your program<br></div><div>traced by lttng-ust ? This should give us the information we need to investigate the<br></div><div>performance profile.<br></div><div><br></div><div>Thanks,<br></div><div><br></div><div>Mathieu<br></div><div><br></div><div><br></div><hr id="zwchr"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><div class="__aliyun_email_body_block"><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">Hi,dev</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"> About a month ago,I asked a question about how to do time recording for ust event when vdso_clock_gettime not availble on my platform（Glibc too old）.Recently I implemented a lib to analyze vdso in memory and lookuped the symbol vdso_clock_gettime successfully.With this vdso_clock_gettime availble,I get a 16% improvement in time spending per ust event. I.E. I measured the time taked by a event with 10 bytes string :</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"> no vdso_clock_gettime : 0.642us</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"> with vdso_clock_gettime：0.554us</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">However，Both the numbers are much higher than the following 0.28us(But closed to 0.5us --W/O opt). So what's the difference between UST(0.28us) and UST W/O OPT(0.5us)?? </div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><img src="cid:__aliyun143010367216577271" alt="" class="__aliyun_inline_attach_1"></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">PS:My hardware</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">2 x Xeon E5-2430 2.20GHz 100MHz FSB (24 cores) 94.6GB / 96GB 1333MHz DDR3 == 6 x 16GB, 6 x empty</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">Thanks</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;">zhenyu.ren</div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div><div class="__aliyun_signature_wrap"></div><div style="font-family:Tahoma,Arial,STHeiti,SimSun;font-size:14px;color:#000000;"><br></div></div><br>_______________________________________________<br>lttng-dev mailing list<br>lttng-dev@lists.lttng.org<br>http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev<br></blockquote><div><br><br></div><div><br></div><div>-- <br></div><div><span name="x"></span>Mathieu Desnoyers<br>EfficiOS Inc.<br>http://www.efficios.com<span name="x"></span><br></div></div></body></html>