Hi all, as I just recently discovered here http://www.ogris.de/blkalloc/ ext4 have some unexpected allocation strategies which can cause some problems in certain scenarios (see the 1/1 patch). This is my attempt to fix this, however I think that this will need some discussion because it changes some of the block allocator heuristic quite significantly and I would like to make sure that it will not hurt our performance in some widely used workloads. Eric, could you run your performance testing with your test suite to see how it performs ? Also, I think that the old behaviour might be quite helpful for SSD because we're not overwriting existing blocks but rather trying to use new one, so the firmware should have easier job. However I do not know how significant impact if at all it might have. If we find out that this is helpful for SSD we might make this conditional depending on the type of the device. Which brings me to the other problem. Since the original behaviour is really bad for thinly provisioned devices we would like to avoid using it even if the underlying storage is SSD, however IIRC there is no way to distinguish this from within the kernel. See the comparison between the old and new allocator behaviour http://people.redhat.com/lczerner/allocator/ Comments and testing is welcomed. Thanks! -Lukas -- 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
