Messages in this thread | | | Date | Tue, 5 Aug 2003 10:50:06 -0700 | From | Andrew Morton <> | Subject | Re: i_blksize |
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Andries.Brouwer@cwi.nl wrote: > > > Looks like I got myself confused > > Yes. But nevertheless, now that you brought this up, > we might consider throwing out i_blksize. > > I am not aware of anybody who actually uses this to give > per-file advice. So, it could be in the superblock.
I suppose so. reiserfs plays with it.
I can't really see that anyone would want to set the I/O size hint on a per-inode basis, especially as the readahead and writebehind code will cheerfully ignore it.
> Any objections?
I don't think it's worth fiddling with at this time, really.
> If sizeof(struct inode) decreases by 1% then we can keep 1% more inodes. > > That reminds me - I threw out i_dev and i_cdev, but Al reintroduced i_cdev. > We should do as some comment says and make a union with i_bdev and i_pipe. > Another 8 bytes gone.
Well all the inode slab caches are using SLAB_HWCACHE_ALIGN at present, so it's a little moot. Especially on a pentium4-compiled kernel.
But I expect most distributed 2.6 kernels will be pII or pIII-compiled. Let's look:
SMP: sizeof(struct ext2_inode_info) = 0x1d0 sizeof(struct ext3_inode_info) = 0x1e0
Both of these pack eight-per-page. Need to get them to 0x1c4 (and remove SLAB_HWCACHE_ALIGN) to get to nine-per-page.
UP: sizeof(struct ext3_inode_info) = 0x1c4 (whew!) sizeof(struct ext2_inode_info) = 0x1b4
So for these filesystems at least, we need to remove SLAB_HWCACHE_ALIGN and we will get a 12% improvement in packing density on uniprocessor.
unionification of i_[bcp]dev sounds like a good idea to give us a little margin there.
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