On Thu, Mar 15, 2012 at 10:34 AM, Andreas Dilger <adilger@xxxxxxxxx> wrote: > On 2012-03-14, at 6:52 PM, Yongqiang Yang wrote: >> Here is a proposal to enable ext4 allocate blocks across group boundary. >> >> Now ext4 allocates blocks within a single block group by locking a >> group. Flex_bg puts metadata blocks together, as a result,it >> enlarges contiguous blocks. So we can enable ext4 allocate blocks >> within a flex block group. Inode allocation takes group lock as block >> allocation, I am not sure if we should allocate inode within single >> group as before. >> >> If we do this, then the new group boundary will be flex block group >> boundary. I am not sure if it is worth doing. > > The maximum extent size is the same as a single block group, so there > is relatively little value in doing this, IMHO. nope. The value comes from 2 aspects: 1. the preallocation can preallocate much more space , 2. if tail blocks of a group and head blocks of the next group is free, then they can be treated as contiguous blocks. I had a rough look at the code, current code does not handle the situation. Yongqiang. > > Cheers, Andreas > > > > > -- Best Wishes Yongqiang Yang -- 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
