Re: Poor performance of pthreads across cpu dies.
Re: Poor performance of pthreads across cpu dies.
- Subject: Re: Poor performance of pthreads across cpu dies.
- From: Terry Lambert <email@hidden>
- Date: Tue, 4 Sep 2007 14:31:35 -0700
On Sep 4, 2007, at 6:09 AM, Andrew Gallatin wrote:
The *NIC* has looked at it, and can easily hash different connections
to several MSI-X interrupt handlers, which are then each bound to
different CPUs (or groups of CPUs).
I am told we support this (Message Signalled Interrupts) for the
latest Intel OS releases, and that it is in fact the preferred method
of interrupt delivery these days, for hardware capable of supporting
it. I wasn't able to find the tech note, which is supposed to have
been published already, according to the author, so you might want to
contact DTS.
Microsoft has though. It is called "receive side scaling" or RSS.
The cleverness is that the NIC and the host has the connections to the
same (sets of) CPUs.
Even in the absence of RSS, multiple MSI-X interrupt handlers, etc,
you can get a decent approximation of a crystal ball by having the
ability to statically bind a single interrupt and a set of hot threads
to set of CPUs. Eg, the administrator is the crystal ball.
It's a little more complex than that when you throw power management
into the Mix, but it's more or less up to the driver author to do the
RSS implementation on top of MSI.
Of course, this requires relatively smart hardware to take full
advantage of it (e.g. Microsoft want segment offloading in the cards,
plus scatter/gather, etc.).
-- Terry
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