Ok, what I am proposing is that the IOMMU is set up when a file is opened to provide the address space required for that file's IO. This remains set up until the file is closed, avoiding frequent set-up and tear-down for each IO transfer.
I assume that there is sufficient IOMMU address space to handle any plausible number of files open, and that it is possible to keep the knowledge of address spaces private to the Primary Ldom, and guests would only be aware of the mbufs visible to them, and this is acceptable. (If you cant trust the Primary, I rather suspect you are stuffed anyway). Clearly, dependent of IOMMU architecture, which I do not claim to understand, this could exhaust IO address space before it exhausts physical memory, I don't know. But I cannot see any other reason why this would not avoid frequent set-up and tear-downs. I get the impression that disk access is not great on my Txxxx machines. I expect a 1GHz T1000 to totally piss on a 4GHz Intel machine at web serving, and it doesn't. (Solaris annoys me too much to even try it, but I assume its better than OpenBSD on Spact64 at this time, or Larry Ellison would have to sell his yacht). On Sat, 20 Oct 2018 at 20:04, Theo de Raadt <dera...@openbsd.org> wrote: > In this case, what do mbufs have to do with files? > > I am very confused. > > > I was assuming that the main objection to allocating mbufs for duration > of > > file open, > > rather than allocating per transfer, this could result in a much higher > > number of mbufs > > being in use concurrently. I cannot see any other downside (which may be > > due to my > > not understanding a lot of stuff - I last wrote this level of stuff for > > Unix in the 1980's). > > > > On Sat, 20 Oct 2018 at 14:41, Theo de Raadt <dera...@openbsd.org> wrote: > > > > > Andrew Grillet <and...@grillet.co.uk> wrote: > > > > > > > These days we are not so short of memory - would it not be possible > to > > > > allocate an mbuf (or two for double-buffered) for each file > > > > when opened, and free when closed? > > > > > > What does this have to do with files?? > > > >
