[Beowulf] Enabling I/OAT and DCA on a live system

Linus Harling linus at ussarna.se
Tue Jul 7 03:46:45 PDT 2009

Hi All, though this might be of interest to someone on the list. It is 
an article about how to enable I/OAT and DCA on a live system or a 
system that hides the option in the BIOS.

According to the post:

"So by using I/OAT the network stack in the Linux kernel can offload 
copy operations to increase throughput. I/OAT also includes a feature 
called Direct Cache Access (DCA) which can deliver data directly into 
processor caches. This is particularly cool because when a network 
interrupt arrives and data is copied to system memory, the CPU which 
will access this data will not cause a cache-miss on the CPU because DCA 
has already put the data it needs in the cache. Sick.

Measurements from the Linux Foundation project indicate a 10% reduction 
in CPU usage, while the Myri-10G NIC website claims they’ve measured a 
40% reduction in CPU usage. For more information describing the 
performance benefits of DCA see this incredibly detailed paper: Direct 
Cache Access for High Bandwidth Network I/O."

Regards /Mostly Lurking

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