From: Evgeniy Polyakov <[EMAIL PROTECTED]> Date: Sun, 5 Mar 2006 04:43:25 +0300
> According to investigation made for kevent based FS AIO reading, > get_user_pages() performange graph looks like sqrt() function > with plato starting on about 64-80 pages on Xeon 2.4Ghz with 1Gb of ram, > while memcopy() is linear, so it can be noticebly slower than > copy_to_user() if get_user_pages() is used aggressively, so userspace > application must reuse the same, already grabbed buffer for maximum > performance, but Intel folks did not provide theirs usage case and any > benchmarks as far as I know. Of course, and programming the DMA controller has overhead as well. This is why would would not use I/O AT with small transfer sizes. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
