in 3.7 kernel, how does 1GB page tables for kernel pagetables affect XFS?

[Linda Walsh]

Dave Chinner wrote:
> On Sat, Jan 19, 2013 at 11:47:44AM -0800, Linda Walsh wrote:
>> Given that XFS relies on the page size for it's maximum block size,
>> does switching to 1GB pages for kernel pagetables allow for larger
>> page-size use in XFS -- and therefore, larger blocksize?
> 
> No, it doesn't. The page cache can't use large pages so there's no
> path to allowing XFS to use larger blocks with them.
> 
> As it is, you'd need a system that supports 16k or 64k page sizes
> for this to be useful, otherwise you just waste a *lot* of memory...
> 
>> Is it something that might be in the not too distant future? ;-)
> 
> I have no plans to do this any time soon - there's no compelling
> reason to do so. I can't speak for anyone else, though...

---
	No prob.. I admit a 1GB page size might be a tad large for
my purposes...  I actually was reading 1MB though even that would be
large...but a GB/disk sector...um...-- at least I'd be likely to
get full speed read & writes if I could fill them...(1GB/R or W
gives me about the fastest overall throughput to my disks).

	Can't test higher (i.e. >=2GB) than that due to getting
partial block read/writes (on a 64 bit machine??)  Sounds like
my LSI controller is only 32bits...but that doesn't seem right...
Maybe it only supports consecutive read/writes up to the limit
of the memory on the controller card..

	All that talk about RAIDs recently, got me depressed a bit
when I realize that while I can get fast speeds, type speeds in seeking
around are about 1/10-1/20th the speed...sigh.

	Might that indicate that I should go with smaller RAIDS with more
spindles?  I.e. instead of 3 groups of RAID5 striped as 0, go for 4-5 groups
of RAID5 striped as a 0?  Just aligning the darn things nearly takes a rocket
scientist!  But then start talking about multiple spindles and optimizing
IOP's...ARG!...;-)  (If it wasn't challenging, I'd find it boring...)...