<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
</head>
<body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
Statically linked excitable works fine. The dynamic linker is probably broken.
<div class=""><br class="">
</div>
<div class="">Hong</div>
<div class="">
<div><br class="">
<blockquote type="cite" class="">
<div class="">On Feb 7, 2020, at 12:53 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com" class="">knepley@gmail.com</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div dir="ltr" style="caret-color: rgb(0, 0, 0); font-family: Verdana; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class="">
<div dir="ltr" class="">On Fri, Feb 7, 2020 at 1:23 PM Zhang, Hong via petsc-dev <<a href="mailto:petsc-dev@mcs.anl.gov" class="">petsc-dev@mcs.anl.gov</a>> wrote:<br class="">
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;">
Hi all,<br class="">
<br class="">
Previously I have noticed that the first call to a CUDA function such as cudaMalloc and cudaFree in PETSc takes a long time (7.5 seconds) on summit. Then I prepared a simple example as attached to help OCLF reproduce the problem. It turned out that the problem
was caused by PETSc. The 7.5-second overhead can be observed only when the PETSc lib is linked. If I do not link PETSc, it runs normally. Does anyone have any idea why this happens and how to fix it?<br class="">
</blockquote>
<div class=""><br class="">
</div>
<div class="">Hong, this sounds like a screwed up dynamic linker. Can you try this with a statically linked executable?</div>
<div class=""><br class="">
</div>
<div class=""> Thanks,</div>
<div class=""><br class="">
</div>
<div class=""> Matt</div>
<div class=""> </div>
<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;">
Hong (Mr.)<br class="">
<br class="">
bash-4.2$ cat ex_simple.c<br class="">
#include <time.h><br class="">
#include <cuda_runtime.h><br class="">
#include <stdio.h><br class="">
<br class="">
int main(int argc,char **args)<br class="">
{<br class="">
clock_t start,s1,s2,s3;<br class="">
double cputime;<br class="">
double *init,tmp[100] = {0};<br class="">
<br class="">
start = clock();<br class="">
cudaFree(0);<br class="">
s1 = clock();<br class="">
cudaMalloc((void **)&init,100*sizeof(double));<br class="">
s2 = clock();<br class="">
cudaMemcpy(init,tmp,100*sizeof(double),cudaMemcpyHostToDevice);<br class="">
s3 = clock();<br class="">
printf("free time =%lf malloc time =%lf copy time =%lf\n",((double) (s1 - start)) / CLOCKS_PER_SEC,((double) (s2 - s1)) / CLOCKS_PER_SEC,((double) (s3 - s2)) / CLOCKS_PER_SEC);<br class="">
<br class="">
return 0;<br class="">
}<br class="">
<br class="">
<br class="">
</blockquote>
</div>
<br clear="all" class="">
<div class=""><br class="">
</div>
--<span class="Apple-converted-space"> </span><br class="">
<div dir="ltr" class="gmail_signature">
<div dir="ltr" class="">
<div class="">
<div dir="ltr" class="">
<div class="">
<div dir="ltr" class="">
<div class="">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br class="">
-- Norbert Wiener</div>
<div class=""><br class="">
</div>
<div class=""><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank" class="">https://www.cse.buffalo.edu/~knepley/</a></div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
<br class="">
</div>
</body>
</html>