I'm hoping someone has seen this before...
I've been trying to track down a performance problem with Linux 3.0.4.
The symptom is system-mode load increasing over time while user-mode
load remains constant while running a data ingest/processing program.
Looking at /proc/meminfo I noticed SUnreclaim increasing steadily.
Looking at /proc/slabinfo I noticed anon_vma and anon_vma_chain also
increasing steadily.
I was able to generate a simple test program that will cause this:
---
#include <unistd.h>
int main(int argc, char *argv[])
{
pid_t pid;
while (1) {
pid = fork();
if (pid == -1) {
/* error */
return 1;
}
if (pid) {
/* parent */
sleep(2);
break;
}
else {
/* child */
sleep(1);
}
}
return 0;
}
---
In the actual program (running as a daemon), a child is reading data
while its parent is processing the previously read data. At any time
there are only a few processes in existence, with older processes
exiting and new processes being fork()ed. Killing the program frees
the slab usage.
I patched the kernel to 3.0.40, but the problem remains. I also
compiled with slab debugging and can see that the growth of anon_vma
and anon_vma_chain is due to anon_vma_clone/anon_vma_fork.
Is this a known issue? Is it fixed in a later release?
Thanks,
--
Daniel K. Forrest Space Science and
dan.forr...@ssec.wisc.edu Engineering Center
(608) 890 - 0558 University of Wisconsin, Madison
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