Lennart Sorensen wrote:
On Tue, Jan 10, 2006 at 09:30:58AM -0700, Jeff V. Merkey wrote:
Bernd Eckenfels wrote:
Here are the patches I use for the splitting. They work well. The
methods employed in Red Hat ES are far better and I am surprised
no one has simply integrated those patches into the kernel which are 4GB
/ 4GB kernel/user.
I was under the impression the 4G/4G split had some non negligable
performance penalties compared to the other options.
It does, but from my testing, I/O performance and app performance seems
negligible. I run the highest performing app/driver
on Linux for disk and network I/O loading and ES3 and ES4 are just as
performant with 4:4 as FC2, FC3, and FC4 with
3:1.
I am now able to capture 4 x gigabit segments with 3:1 at sustained
stream to disk rates of 497 MB/S
and 1 x 10Gbe at 517 MB/S stream to disk. I see no appreciable
performance differences 3:1 vs. 4:4. Modern Xeon
processors have gotten a lot better dealing with TLB invalidation. I
suppose applications that remap
memory all over the place or that do tons of swapping would see some
penalty, and I do see some
performance degredation when user space apps start swapping, but it's
difficult to quantify how much is related
to disk I/O latency vs. TLB overhear. Most TLB flushes will cost you 150
clocks over time as the TLB reloads
itself.
Jeff
Len Sorensen
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