Ext4 Developer Interlock Call: 04-23-07 Minutes
Attendees: Mingming Cao, Dave Kleikamp, Avantika Mathur, Ted Ts'o, Suparna Bhattacharya, Jean-Pierre Dion, Jean Noel Cordenner, Valérie Clément, Jose Santos
Minutes can be accessed at: http://ext4.wiki.kernel.org/index.php/Ext4_Developer%27s_Conference_Call
- Mingming proposed moving back to 8am PST meeting time, since the 6am time is inconvenient for
a few people. This discussion will be continued through email, to find a time which works for everyone.
- Next week's meeting will be canceled, unless there is anyone who would like to request a meeting.
- Mingming will be updating the git tree with extents-fix patches from Alex, i_flags patch from Honza, i_extra_isize patch from Kalpak.
Uninitialized Block Groups:
- The patch sent out by Andreas is against 2.6.16 and ext3. Need to port this to current ext4, test and then add to git-tree. Avantika will ask Andreas if he needs help with this.
- There is a patch to export JDB statistics to /proc. In order to get this patch to mainline, there needs to be discussion about the correct place for the statistics; /proc or perhaps debugfs.
- Ted will post the current e2fsprogs patches in progress. Ted has been working with these patches and making changes.
- Main work areas for making e2fsprogs compatible with extents and 64-bit.
- block iterator: make a block iterator work with both extent and non-extent code. Code that is oblivious to extents will still work with the block iterator. This has been written by Andreas Dilger.
- extents: in order to preserve ABI compatibility, support for a new interface for extents which uses 64-bit logical and physical block numbers. The block iterator then translate from on-disk to in-memory format. This will allow for possible future increases of physical and logical block sizes in extents, without breaking ABI.
- bitmaps in e2fsprogs: this will be discussed in more detail at the next meeting, after people have a chance to read related email.
- fallocate syscall interface: the current plan, based on discussions on the mailing list, is to create a separate wrapper for s390 in glibc. Using regular parameter ordering for all other architectures, but a different order on s390. Jakub Jelinek has said that the changes in glibc can be made pretty easily.
- The preallocation patches in the ext4 git-tree are outdated, using the ioctl interface. Once Amit re-posts the patches with the syscall interface, they will be updated in the git-tree as well.
- Mingming mentioned the need to flush preallocation metadata changes to disk if file size or file content is being tested. Discussed doing an fsync at Bmap time.
TESTING extents testing
- Discussed methods for testing extents on highly fragmented filesystems.
- Jose will look into possible tests, including perhaps using the 'aged' option in FFSB
- Ted suggested creating a mountoption that creates a bad block allocator which it jumps to a new block group every 8 blocks. This would force a very large number of extents, and may be a good test for extents.
- We would like to perform more testing on large (>16TB) filesystems
- currently hardware limitations are preventing this testing. We have tested 10TB raid dists, and 16TB loopback devices. Avantika will look into creating very large sparse devices for testing.
Large file deletion
- Valerie had recently tested large file deletion on ext3/4, but did not see the expected performance gain with ext4 due to compact metadata when using extents.
- Valerie will try re-running the test. Jose will also be looking into this test.