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* [XFS] Lazy Superblock CountersDavid Chinner2007-07-141-8/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When we have a couple of hundred transactions on the fly at once, they all typically modify the on disk superblock in some way. create/unclink/mkdir/rmdir modify inode counts, allocation/freeing modify free block counts. When these counts are modified in a transaction, they must eventually lock the superblock buffer and apply the mods. The buffer then remains locked until the transaction is committed into the incore log buffer. The result of this is that with enough transactions on the fly the incore superblock buffer becomes a bottleneck. The result of contention on the incore superblock buffer is that transaction rates fall - the more pressure that is put on the superblock buffer, the slower things go. The key to removing the contention is to not require the superblock fields in question to be locked. We do that by not marking the superblock dirty in the transaction. IOWs, we modify the incore superblock but do not modify the cached superblock buffer. In short, we do not log superblock modifications to critical fields in the superblock on every transaction. In fact we only do it just before we write the superblock to disk every sync period or just before unmount. This creates an interesting problem - if we don't log or write out the fields in every transaction, then how do the values get recovered after a crash? the answer is simple - we keep enough duplicate, logged information in other structures that we can reconstruct the correct count after log recovery has been performed. It is the AGF and AGI structures that contain the duplicate information; after recovery, we walk every AGI and AGF and sum their individual counters to get the correct value, and we do a transaction into the log to correct them. An optimisation of this is that if we have a clean unmount record, we know the value in the superblock is correct, so we can avoid the summation walk under normal conditions and so mount/recovery times do not change under normal operation. One wrinkle that was discovered during development was that the blocks used in the freespace btrees are never accounted for in the AGF counters. This was once a valid optimisation to make; when the filesystem is full, the free space btrees are empty and consume no space. Hence when it matters, the "accounting" is correct. But that means the when we do the AGF summations, we would not have a correct count and xfs_check would complain. Hence a new counter was added to track the number of blocks used by the free space btrees. This is an *on-disk format change*. As a result of this, lazy superblock counters are a mkfs option and at the moment on linux there is no way to convert an old filesystem. This is possible - xfs_db can be used to twiddle the right bits and then xfs_repair will do the format conversion for you. Similarly, you can convert backwards as well. At some point we'll add functionality to xfs_admin to do the bit twiddling easily.... SGI-PV: 964999 SGI-Modid: xfs-linux-melb:xfs-kern:28652a Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Tim Shimmin <tes@sgi.com>
* [XFS] Reduce endian flipping in alloc_btree, same as was done forEric Sandeen2006-09-281-51/+57
| | | | | | | | | | | ialloc_btree. SGI-PV: 955302 SGI-Modid: xfs-linux-melb:xfs-kern:26910a Signed-off-by: Eric Sandeen <sandeen@sandeen.net> Signed-off-by: Nathan Scott <nathans@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
* [XFS] use NULL for pointer initialisation instead of zero-cast-to-ptrNathan Scott2006-09-281-4/+4
| | | | | | | | SGI-PV: 954580 SGI-Modid: xfs-linux-melb:xfs-kern:26562a Signed-off-by: Nathan Scott <nathans@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
* [XFS] remove left over INT_ comments in *alloc*.c We can verify endianessChristoph Hellwig2006-09-281-8/+8
| | | | | | | | | | | handling with sparse now, no need for comments. SGI-PV: 954580 SGI-Modid: xfs-linux-melb:xfs-kern:26557a Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Nathan Scott <nathans@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
* [XFS] Remove version 1 directory code. Never functioned on Linux, justNathan Scott2006-06-201-2/+0
| | | | | | | | | pure bloat. SGI-PV: 952969 SGI-Modid: xfs-linux-melb:xfs-kern:26251a Signed-off-by: Nathan Scott <nathans@sgi.com>
* [XFS] Endianess annotations for various allocator data structuresChristoph Hellwig2005-11-021-205/+208
| | | | | | | | SGI-PV: 943272 SGI-Modid: xfs-linux:xfs-kern:201006a Signed-off-by: Christoph Hellwig <hch@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>
* [XFS] silence gcc4 warnings. the directory ones are wrong because ofChristoph Hellwig2005-11-021-0/+8
| | | | | | | | | | | information gcc could not find out (that a directory always has a .. entry), the others are outright gcc bugs. SGI-PV: 943511 SGI-Modid: xfs-linux:xfs-kern:200055a Signed-off-by: Christoph Hellwig <hch@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>
* [XFS] Update license/copyright notices to match the prefered SGINathan Scott2005-11-021-25/+11
| | | | | | | | | boilerplate. SGI-PV: 913862 SGI-Modid: xfs-linux:xfs-kern:23903a Signed-off-by: Nathan Scott <nathans@sgi.com>
* [XFS] Remove xfs_macros.c, xfs_macros.h, rework headers a whole lot.Nathan Scott2005-11-021-8/+10
| | | | | | | SGI-PV: 943122 SGI-Modid: xfs-linux:xfs-kern:23901a Signed-off-by: Nathan Scott <nathans@sgi.com>
* Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds2005-04-161-0/+2204
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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