Re: [BProc] vmadump performance

[Grant T. <gt...@sw...>]

>>>>> Erik Arjan Hendriks <er...@he...> writes:

> I find it surprising that the cache stuff is so expensive.  Is the
> hardware somewhat lacking in maintaining coherency between CPUs?

No, the whole cache is on die along with the cores.  Coherency is
"free" to some extent, since both cores share most of the cache.  It's
also "free" wrt DMA, as many of the key periperals are on the inside
of the cache and not the outside.

What's not free is icache flushes, because in addition to being a
little expensive by themselves, they occupy all cores by doign a nasty
interprocess function call.  Doing this for every page is a lot of
work.

I also ended up skipping the brute force zero compare on the freezing
side.  In our application we don't have many private pages which are
full of zeroes, so we come out a little bit ahead here.

--
Grant Taylor - x285 - http://pasta/~gtaylor/
Starent Networks - +1.978.851.1185