On Fri, Nov 07, 2008 at 09:43:11AM -0500, Theodore Tso wrote: > The one thing we might need for SSD-friendly allocation policies is to > tell the allocators to not try so hard to make sure allocations are > contiguous, but there are other reasons why you want contiguous > extents anyway (such as reducing the size of your extent tree and > reducing the number of block allocation data structures that need to > be updated). And, I think to some extent SSD's do care to some level > about contiguous extents, from the point of view of reducing scatter > gather operations if nothing else, right? It's not so much s-g operations as it is that you can only have 32 commands outstanding with the drive at any given time. Each read/write command can specify only one extent. So if you can ask for one 256k extent rather than have to ask for a 4k extent 64 times, you're going to get your data faster. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
