I didn't realize the xen kernel of RHEL 5 was not numa aware, I figured this out today after trying to run numactl --hardware. I switched RHEL 5 to boot off the other default kernel, which is NUMA aware and everything works!
<br><br>Hopefully this will be helpful for someone else in the future.<br>Thanks<br>Jeremy<br><br><div><span class="gmail_quote">On 9/24/07, <b class="gmail_sendername">Jeremy Fleming</b> <<a href="mailto:firstname.lastname@example.org">
email@example.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">I have a quad opteron node machine where each node is a dual core with each core running at
2.0Gz. The machine has 64 GB of ram, two broadcom ethernet gigabit cards and 2 other gigabit intel cards each supplying 2 ports, and are supported by the e1000 driver. The machine is running the default install of Redhat Enterprise
5.0 (original release, no patches or updates).<br><br><br>Remote machines are supplying ~512 megabit/sec streams over gigabit ethernet to this machine. There are two streams on seperate ethernet lines. I have each stream connected to a different port on one of the intel cards. The streams are sent via multicast, and there are 4 sub-streams per ethernet line. Each substream is approximately
131.072 megabits/sec.<br><br>On the opteron machine I have a process that can pull a substream off of an ethernet port and dump it to a ring buffer in shared memory. To start, the process could never keep up with receiving the data via ethernet and then doing a memcpy to shared memory. Then I found out about NUMA, and decided to use sched_setaffinity to bind the process to a cpu, I bound the process to the same cpu the ethernet card is bound to via it's IRQ.
<br><br>I looked in /proc/interrupts and found "eth0" or "eth1", looked up it's IRQ, then went into /proc/irq/<eth 0 IRQ>/smp_affinity, and checked which cpu the IRQ was bound to. I bound the process to that processor and ran it again. Luckily no data loss and it could keep up. I bound the process before I allocated memory so the memory was bound to the same process too. I was even able to run three more processes, bound to the same cpu and have all 4 read the sub-streams from the ethernet device eth0, with no data loss. I can even run another process which reads from the ring buffer and dumps the data to disk and it causes no slow downs or data loss.
<br><br>Now I want to read a substream from the other stream connected to eth1 while reading from the other 4 sub-streams. I start that up just by binding the same application to the processor associated with eth 1, by checking "/proc/irq/<eth 1 IRQ>/smp_affinity". When the process starts the system starts to not be able to keep up anymore, just like in the beginning when I just had 1 processor reading one stream without doing anything else. I thought I was just trying to do too much work, so I turned off all streams, and ran just two processes bound to two different processors, each bound to the same processor as the associated eth device. I ran them both, and they lose data. If I run them seperately they work fine, but when I read 1 sub-stream from each of the two unique streams they fail.
<br><br>Are the two ethernet devices dumping their multicast data into kernel buffers associated with different processors? <br>How do I know what processor the kernel ethernet buffers are associated with? <br>Is there a way to set cpuaffinity for ethernet devices before they boot up so I know which processors memory they are dumping data to?
<br>Any ideas on why there would be a problem with reading a stream from each eth device at the same time and not with reading 4 streams from one eth device? <br>Do I need to turn a NUMA aware scheduler on somehow, or is that on by default in RHEL 5?
<br>I also noticed that linux assigns IRQs at bootup that vary with each boot, is there a way to statically assign IRQs to the ethernet cards? <br><br>Any help or pointers at all would be great!<br><br>Thanks in advance