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[Xen-devel] vsyscalls may be going away... impact on Xen time performance on Linux in the future?



Hmmm...

It appears that Xen time mechanisms that use vsyscall may be
getting slower...

"This is a significant performance penalty (~220ns here) for
all vsyscall users, but there aren't many left."

http://lwn.net/Articles/446220/ 

I honestly don't remember all the details myself anymore,
but I think this means that user apps in Xen PV domains
that call gettimeofday a *lot* may be in for a bit of
a shock when they move to a 3.x kernel in the future.
(Many enterprise apps do things like timestamp transactions,
which can lead to 10s of thousands of gettimeofday's
per second.)

See the xen-devel discussion here:

http://lists.xensource.com/archives/html/xen-devel/2010-10/msg00872.html 

Dan

P.S. For lwn subscribers (or non-subscribers willing to wait a week),
see Jonathan Corbet's nice overview at http://lwn.net/Articles/446125/ 

--

Thanks... for the memory!
I really could use more / my throughput's on the floor
The balloon is flat / my swap disk's fat / I've OOM's in store
Overcommitted so much
(with apologies to Bob Hope)


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