On 7/18/13 1:53 PM, Theodore Ts'o wrote: > On Thu, Jul 18, 2013 at 01:35:24PM -0500, Eric Sandeen wrote: >>> (Should we do this all the time, instead of when the application >>> explicitly requests it? Maybe; there could be cases with very large, >>> fragmented files accessed by an application such as "file" is only needs >>> to look at a small subset of the file where this could result in an >>> unnecessary work and memory allocated. OTOH, 95%+ of the time this >>> would probably be a win...) >> >> I'd say yes, we should - maybe not in all cases but if you need it for >> AIO, try to make it "all the time" at least for that AIO? > > The problem is we don't know that we're doing AIO until we see the > first io_submit(2) call. With this patch series, we'll pull the > contents of the entire leaf tree block into extent cache, but if the > extent tree is larger than that, if we read in the entire extent tree > on the first AIO request, then that first request will delayed even > more, and it's not clear that's a good thing. Is blocking on a pre-AIO ioctl better than blocking on the first AIO? -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
