Le mardi 23 septembre 2008 à 17:13 -0600, Andreas Dilger a écrit : > On Sep 22, 2008 11:32 +0200, Fr�d�ric Boh� wrote: > > Le lundi 22 septembre 2008 à 14:17 +0530, Aneesh Kumar K.V a écrit : > > > What you can do is make ext4_group_info generic for both mballoc and > > > oldalloc. We can then add bg_flag to the in memory ext4_group_info > > > that would indicate whether the group is initialized or not. Here > > > initialized for an UNINIT_GROUP indicate we have done > > > ext4_init_block_bitmap on the buffer_head. Then > > > instead of depending on the buffer_head uptodate flag we can check > > > for the ext4_group_info bg_flags and decided whether the block/inode > > > bitmap need to be initialized. > > > > That makes sense ! I agree with you, we need an additional in-memory > > flag to know whether buffers are initialized or not. Anyway, making > > ext4_group_info generic will lead to unneeded memory consumption for > > oldalloc. Maybe a simple independent bits array could do the trick. Is > > there any advantage to re-use ext4_group_info ? > > For ext4 I think 99% of users will use mballoc, and the reduction in code > complexity is itself useful. I don't think the in-memory overhead is very > much, maybe 1 MB per TB of filesystem space. > You are right ext4_group_info structure was not as big as I thought. Do you mean that making ext4_group_info generic for both mballoc and oldalloc will reduce the code complexity ? > Also, if you are considering this approach (to initialize the in-memory > bitmaps at mount time) they should be written to disk even if unused. > Please also consider doing the inode table zeroing at the same time. > This would allow uninit_bg to avoid doing it at mke2fs time. In fact, I was not considering doing this at mount time, but it could be a good approach. Anyway, I don't understand why we should write bitmaps to disk after that, and why we should zeroing the inode table. Don't we end up with a fast mkfs and a slow mount doing all the stuff older mkfs was doing ? The UNINIT feature would become less interesting. Regards, Frederic -- 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
