On Fri, Oct 28, 2011 at 02:28:20PM -0400, John Stoffel wrote: > and service. How would TM benefit me? I don't use Xen, don't want to > play with it honestly because I'm busy enough as it is, and I just > don't see the hard benefits. If you used Xen tmem would be more or less the equivalent of cache=writethrough/writeback. For us tmem is the linux host pagecache running on the baremetal in short. But at least when we vmexit for a read we read 128-512k of it (depending on if=virtio or others and guest kernel readahead decision), not just a fixed absolutely worst case 4k unit like tmem would do... Without tmem Xen can only work like KVM cache=off. If at least it would drop us a copy, but no, it still does the bounce buffer, so I'd rather bounce in the host kernel function file_read_actor than in some superflous (as far as KVM is concerned) tmem code, plus we normally read orders of magnitude more than 4k in each vmexit, so our default cache=writeback/writethroguh may already be more efficient than if we'd use tmem for that. We could only consider for swap compression but for swap compression I've no idea why we still need to do a copy, instead of just compressing from userland page in zerocopy (worst case using any mechanism introduced to provide stable pages). And when host linux pagecache will go hugepage we'll get a >4k copy in one go while tmem bounce will still be stuck at 4k... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>