lkml.org 
[lkml]   [2007]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: irq load balancing
From
On Thu, Sep 13, 2007 at 01:31:39PM -0700, Venkat Subbiah wrote:
> Doing it in a round-robin fashion will be disastrous for performance.
> Your cache miss rate will go through the roof and you'll hit the slow
> paths in the network stack most of the time.
> > Most of the work in my system is spent in enrypt/decrypting traffic.
> Right now all this is done in a tasklet within the softirqd and hence
> all landing up on the same CPU.
> On the receive side it'a packet handler that handles the traffic. On the
> tx side it's done within the transmit path of the packet. So would
> re-architecting this to move the rx packet handler to a different kernel
> thread(with smp affinity to one CPU) and tx to a different kernel
> thread(with SMP affinity to a different CPU) be advisable.
> What's the impact on cache miss and slowpath/fastpath in network stack.

Since most network devices have a single status register for both
receiver and transmit (and errors and the like), which needs a lock to
protect access, you will likely end up with serious thrashing of moving
the lock between cpus.

--
Len Sorensen
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-09-13 22:47    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site