Date: Fri, 30 May 2014 23:27:01 +0200 From: Nils Beyer <nbe@renzel.net> To: freebsd-virtualization@freebsd.org Subject: Re: Bheve: Slow linux syscalls on AMD References: <5388B56D.1000501@digiware.nl>
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Hi Willem,
Willem Jan Withagen wrote:
> 1) I'm looking for a better basic syscall in Linux that is not cache,
> faked or otherwise tweaked to nog give what I want.
> Would really be nice if there was a NOP_syscall, just go in and out of
> kernel space.....
Hmm, I've tried your test with "getuid". Seems not to be cached. Here's the
diff:
===============================================================================
# diff 0.orig.c 0.c
24c24
< j=getpid();
---
> (void)getuid();
38c38
< printf("Average time for System call getpid : %f\n",avgTimeSysCall);
---
> printf("Average time for System call getuid : %f\n",avgTimeSysCall);
===============================================================================
And here is the result:
===============================================================================
# strace -c ./0
Average time for System call getuid : 10564.581055
Average time for Function call : 2.285000
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
100.00 0.004590 0 1000000 getuid
0.00 0.000000 0 1 read
0.00 0.000000 0 2 write
0.00 0.000000 0 2 open
0.00 0.000000 0 2 close
0.00 0.000000 0 3 fstat
0.00 0.000000 0 9 mmap
0.00 0.000000 0 3 mprotect
0.00 0.000000 0 1 munmap
0.00 0.000000 0 1 brk
0.00 0.000000 0 1 1 access
0.00 0.000000 0 1 execve
0.00 0.000000 0 1 arch_prctl
------ ----------- ----------- --------- --------- ----------------
100.00 0.004590 1000027 1 total
===============================================================================
> 3) Can somebody do the same test on an intel plaform and see what the
> results are.
Here is the result from a bhyved CentOS on an Intel i3:
===============================================================================
# strace -c ./0.orig
Average time for System call getpid : 3.776000
Average time for Function call : 2.326000
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
-nan 0.000000 0 1 read
-nan 0.000000 0 2 write
-nan 0.000000 0 2 open
-nan 0.000000 0 2 close
-nan 0.000000 0 3 fstat
-nan 0.000000 0 9 mmap
-nan 0.000000 0 3 mprotect
-nan 0.000000 0 1 munmap
-nan 0.000000 0 1 brk
-nan 0.000000 0 1 1 access
-nan 0.000000 0 1 getpid
-nan 0.000000 0 1 execve
-nan 0.000000 0 1 arch_prctl
------ ----------- ----------- --------- --------- ----------------
100.00 0.000000 28 1 total
===============================================================================
Regards,
Nils
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