On Fri, 2 Mar 2007, Nick Piggin wrote: > > >From the I/O controller and from the application. > > Why doesn't the application need to deal with TLB entries?
Because it may only operate on a small section of the file and hopefully splice the rest through? But yes support for mmapped I/O would be necessary. > > This would only be a temporary fix pushing the limits to the double or so? > > And using slightly larger page sizes isn't? There was no talk about slightly. 1G page size would actually be quite convenient for some applications. > > Amortized? The controller still would have to hunt down the 4kb page > > pieces that we have to feed him right now. Result: Huge scatter gather > > lists that may themselves create issues with higher page order. > > What sort of numbers do you have for these controllers that aren't > very good at doing sg? Writing a terabyte of memory to disk with handling 256 billion page structs? In case of a system with 1 petabyte of memory this may be rather typical and necessary for the application to be able to save its state on disk. > Isn't the issue was something like your IO controllers have only a > limited number of sg entries, which is fine with 16K pages, but with > 4K pages that doesn't give enough data to cover your RAID stripe? > > We're never going to do a variable sized pagecache just because of that. No, we need support for larger page sizes than 16k. 16k has not been fine for a couple of years. We only agreed to 16k because that was the common consensus. Best performance was always at 64k 4 years ago (but then we have no numbers for higher page sizes yet). Now we would prefer much larger sizes. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
