Re: cap on writeback?

2013-03-26 Thread Raymond Jennings
On Mon, Mar 25, 2013 at 8:17 PM, valdis.kletni...@vt.edu wrote: On Mon, 25 Mar 2013 17:23:40 -0700, Raymond Jennings said: Is there some sort of mechanism that throttles the size of the writeback pool? There's a lot of tunables in /proc/sys/vm - everything from drop_caches to swappiness

what does the kernel does after it is being notified of incoming Frame

2013-03-26 Thread Tarun Batra
Hello All, I was trying to search what happen when the kernel is being notified of the incoming Frame. I studied Chapter 10. Frame Reception Of Understanding Linux Network Internals. I only tells how the kernel is notified of the coming frame. But what does the kernel does after it is being

SSDs vs elevators (was Re: cap on writeback?)

2013-03-26 Thread Arlie Stephens
On Mar 25 2013, valdis.kletni...@vt.edu wrote: Just for the record, most of my high-performance stuff runs best with the noop scheduler - when you're striping I/O across several hundred disks, the last thing you want is some some single-minded disk scheduler re-arranging the I/Os and

Re: what does the kernel does after it is being notified of incoming Frame

2013-03-26 Thread Rami Rosen
Hi, Can you give me more references even linked videos. You might want to take a look in section 6, Receiving a packet, in Linux Kernel Networking (free 189 pages doc). see: http://media.wix.com/ugd//295986_4ef6dbdf11fd0a7f74f09741b4b5b2ee.pdf (A shameless plug as I wrote it...) rgs, Rami

relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Kumar amit mehta
Hi All, I was reading some stuff on interrupts and irq lines today and I thought I'll expermient with the network rx path. To start with, I've a Virtual Machine running 3.8 linux kernel. My machine has 4 CPU cores, network (eth) interface is driven by pcnet_32 AMD driver and is tied to IRQ line

Re: relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Arlie Stephens
Hi Amit, On Mar 26 2013, Kumar amit mehta wrote: Hi All, I was reading some stuff on interrupts and irq lines today and I thought I'll expermient with the network rx path. To start with, I've a Virtual Machine running 3.8 linux kernel. My machine has 4 CPU cores, network (eth) interface

Re: relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Rami Rosen
Hi, Kumar, 1) Regarding rx queues: what does ls /sys/class/net/eth0/queues show ? 2) can you try setting affinity for working only with CPU3 and see what happens after some traffic is sent by cat /proc/interrupts? regards, Rami Rosen http://ramirose.wix.com/ramirosen On Tue, Mar 26, 2013 at

Re: relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Kumar amit mehta
On Tue, Mar 26, 2013 at 11:45:55AM -0700, Arlie Stephens wrote: I don't know for sure what linux does, but the NICs I've seen with multiple queues tend to select queues by hashing incoming packets based on source IP, sourse port, destination IP, destination port and (if TCP) protocol.

Re: relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Kumar amit mehta
On Tue, Mar 26, 2013 at 08:35:56PM +0200, Rami Rosen wrote: 1) Regarding rx queues: what does ls /sys/class/net/eth0/queues show ? $ ls /sys/class/net/eth0/queues rx-0 tx-0 2) can you try setting affinity for working only with CPU3 and see what happens after some traffic is sent by cat

Re: relationship between cpu_affinity and Packet RX Processing

2013-03-26 Thread Rami Rosen
Hi, 1) You can be sure that it does not use more than one rx queue. You can find more info about RX queues in http://media.wix.com/ugd//295986_4ef6dbdf11fd0a7f74f09741b4b5b2ee.pdf (I wrote it, a shameless plug...) 2) Does the irqbalance service, which is common in some distros, is running ?