<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div>I modified the source code to show exactly how many clock ticks it is taking for each call. It seems that the behavior hinted by Mauro Romano Trajber is actually there:</div><div><div>[enrico@espresso ~]$ ./syscallperf 15</div><div>4925</div><div>1190</div><div>942</div><div>942</div><div>935</div><div>942</div><div>636</div><div>577</div><div>627</div><div>621</div><div>580</div><div>591</div><div>565</div><div>580</div><div>565</div></div><div><br></div><div>I am starting to wonder if this depends on the syscall itself OR on some call optimization.. any gcc experts around?</div><div><br><div>
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><i>Enrico Granata</i></div></div><div><i>Computer Science & Engineering Department (EBU3B) - </i><i>Room 3240</i></div><div><i>office phone 858 534 9914</i></div><div><i>University of California, San Diego</i></div></div></span></div></span></span></div></div></div></span></div></span></div></span></div></div>
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<br><div><div>On Feb 25, 2011, at 12:30 PM, Mauro Romano Trajber wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Sure, the code is attached.<div><div><div><br><br><div class="gmail_quote">On Fri, Feb 25, 2011 at 5:15 PM, Daniel Baluta <span dir="ltr"><<a href="mailto:daniel.baluta@gmail.com">daniel.baluta@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im">On Fri, Feb 25, 2011 at 8:22 PM, Mauro Romano Trajber <<a href="mailto:trajber@gmail.com">trajber@gmail.com</a>> wrote:<br>
> Thanks Enrico and Daniel, you're right. glibc was caching getpid(); but this<br>
> is not the root cause of this behavior.<br>
> Going further, I decide to use call getpid without glibc, using<br>
> syscall(SYS_getpid) to test this behavior and it happened again.<br>
> Calling it once, the test consumes about 7k CPU cycles and 10 calls consumes<br>
> about 10k CPU cycles.<br>
> Any ideas ?<br>
<br>
</div>Can you post a pointer to your code and information about how you got<br>
this numbers?<br>
<br>
thanks,<br>
<font color="#888888">Daniel.<br>
</font></blockquote></div><br></div></div></div>
<span><syscallperf.c></span></blockquote></div><br></div></body></html>