Re: [PLEASE-TESTME] Zerocopy networking patch, 2.4.0-1

[Jamie Lokier]

Ingo Molnar wrote:
> > > well, this is a performance problem if you are using threads. For normal
> > > processes there is no need for a SMP cross-call, there TLB flushes are
> > > local only.
> > >
> > But that would be ugly as hell:
> > so apache 2.0 would become slower with MSG_NOCOPY, whereas samba 2.2
> > would become faster.
> 
> there *is* a cost of having a shared VM - and this is i suspect
> unavoidable.

Is it possible to avoid the SMP cross-call in the case that the other
threads have neither accessed nor dirtied the page in question?

One way to implement this is to share VMs but not the page tables, or to
share parts of the page tables that don't contain writable pages.

Just a sudden inspired thought...  I don't know if it is possible or
worthwhile.

enjoy,
-- Jamie