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path: root/fs/btrfs/free-space-cache.h
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2011-04-25Btrfs: Support reading/writing on disk free ino cacheLi Zefan
This is similar to block group caching. We dedicate a special inode in fs tree to save free ino cache. At the very first time we create/delete a file after mount, the free ino cache will be loaded from disk into memory. When the fs tree is commited, the cache will be written back to disk. To keep compatibility, we check the root generation against the generation of the special inode when loading the cache, so the loading will fail if the btrfs filesystem was mounted in an older kernel before. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2011-04-25Btrfs: Cache free inode numbers in memoryLi Zefan
Currently btrfs stores the highest objectid of the fs tree, and it always returns (highest+1) inode number when we create a file, so inode numbers won't be reclaimed when we delete files, so we'll run out of inode numbers as we keep create/delete files in 32bits machines. This fixes it, and it works similarly to how we cache free space in block cgroups. We start a kernel thread to read the file tree. By scanning inode items, we know which chunks of inode numbers are free, and we cache them in an rb-tree. Because we are searching the commit root, we have to carefully handle the cross-transaction case. The rb-tree is a hybrid extent+bitmap tree, so if we have too many small chunks of inode numbers, we'll use bitmaps. Initially we allow 16K ram of extents, and a bitmap will be used if we exceed this threshold. The extents threshold is adjusted in runtime. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2011-04-25Btrfs: Make free space cache code genericLi Zefan
So we can re-use the code to cache free inode numbers. The change is quite straightforward. Two new structures are introduced. - struct btrfs_free_space_ctl We move those variables that are used for caching free space from struct btrfs_block_group_cache to this new struct. - struct btrfs_free_space_op We do block group specific work (e.g. calculation of extents threshold) through functions registered in this struct. And then we can remove references to struct btrfs_block_group_cache. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2011-04-25Btrfs: Remove unused btrfs_block_group_free_space()Li Zefan
We've already recorded the value in block_group->frees_space. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
2011-03-28Btrfs: add btrfs_trim_fs() to handle FITRIMLi Dongyang
We take an free extent out from allocator, trim it, then put it back, but before we trim the block group, we should make sure the block group is cached, so plus a little change to make cache_block_group() run without a transaction. Signed-off-by: Li Dongyang <lidongyang@novell.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2010-10-29Btrfs: load free space cache if it existsJosef Bacik
This patch actually loads the free space cache if it exists. The only thing that really changes here is that we need to cache the block group if we're going to remove an extent from it. Previously we did not do this since the caching kthread would pick it up. With the on disk cache we don't have this luxury so we need to make sure we read the on disk cache in first, and then remove the extent, that way when the extent is unpinned the free space is added to the block group. This has been tested with all sorts of things. Signed-off-by: Josef Bacik <josef@redhat.com>
2010-10-29Btrfs: write out free space cacheJosef Bacik
This is a simple bit, just dump the free space cache out to our preallocated inode when we're writing out dirty block groups. There are a bunch of changes in inode.c in order to account for special cases. Mostly when we're doing the writeout we're holding trans_mutex, so we need to use the nolock transacation functions. Also we can't do asynchronous completions since the async thread could be blocked on already completed IO waiting for the transaction lock. This has been tested with xfstests and btrfs filesystem balance, as well as my ENOSPC tests. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
2010-10-28Btrfs: create special free space cache inodeJosef Bacik
In order to save free space cache, we need an inode to hold the data, and we need a special item to point at the right inode for the right block group. So first, create a special item that will point to the right inode, and the number of extent entries we will have and the number of bitmaps we will have. We truncate and pre-allocate space everytime to make sure it's uptodate. This feature will be turned on as soon as you mount with -o space_cache, however it is safe to boot into old kernels, they will just generate the cache the old fashion way. When you boot back into a newer kernel we will notice that we modified and not the cache and automatically discard the cache. Signed-off-by: Josef Bacik <josef@redhat.com>
2009-07-24Btrfs: use hybrid extents+bitmap rb tree for free spaceJosef Bacik
Currently btrfs has a problem where it can use a ridiculous amount of RAM simply tracking free space. As free space gets fragmented, we end up with thousands of entries on an rb-tree per block group, which usually spans 1 gig of area. Since we currently don't ever flush free space cache back to disk this gets to be a bit unweildly on large fs's with lots of fragmentation. This patch solves this problem by using PAGE_SIZE bitmaps for parts of the free space cache. Initially we calculate a threshold of extent entries we can handle, which is however many extent entries we can cram into 16k of ram. The maximum amount of RAM that should ever be used to track 1 gigabyte of diskspace will be 32k of RAM, which scales much better than we did before. Once we pass the extent threshold, we start adding bitmaps and using those instead for tracking the free space. This patch also makes it so that any free space thats less than 4 * sectorsize we go ahead and put into a bitmap. This is nice since we try and allocate out of the front of a block group, so if the front of a block group is heavily fragmented and then has a huge chunk of free space at the end, we go ahead and add the fragmented areas to bitmaps and use a normal extent entry to track the big chunk at the back of the block group. I've also taken the opportunity to revamp how we search for free space. Previously we indexed free space via an offset indexed rb tree and a bytes indexed rb tree. I've dropped the bytes indexed rb tree and use only the offset indexed rb tree. This cuts the number of tree operations we were doing previously down by half, and gives us a little bit of a better allocation pattern since we will always start from a specific offset and search forward from there, instead of searching for the size we need and try and get it as close as possible to the offset we want. I've given this a healthy amount of testing pre-new format stuff, as well as post-new format stuff. I've booted up my fedora box which is installed on btrfs with this patch and ran with it for a few days without issues. I've not seen any performance regressions in any of my tests. Since the last patch Yan Zheng fixed a problem where we could have overlapping entries, so updating their offset inline would cause problems. Thanks, Signed-off-by: Josef Bacik <jbacik@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-06-10Btrfs: add mount -o ssd_spread to spread allocations outChris Mason
Some SSDs perform best when reusing block numbers often, while others perform much better when clustering strictly allocates big chunks of unused space. The default mount -o ssd will find rough groupings of blocks where there are a bunch of free blocks that might have some allocated blocks mixed in. mount -o ssd_spread will make sure there are no allocated blocks mixed in. It should perform better on lower end SSDs. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2009-04-03Btrfs: rework allocation clusteringChris Mason
Because btrfs is copy-on-write, we end up picking new locations for blocks very often. This makes it fairly difficult to maintain perfect read patterns over time, but we can at least do some optimizations for writes. This is done today by remembering the last place we allocated and trying to find a free space hole big enough to hold more than just one allocation. The end result is that we tend to write sequentially to the drive. This happens all the time for metadata and it happens for data when mounted -o ssd. But, the way we record it is fairly racey and it tends to fragment the free space over time because we are trying to allocate fairly large areas at once. This commit gets rid of the races by adding a free space cluster object with dedicated locking to make sure that only one process at a time is out replacing the cluster. The free space fragmentation is somewhat solved by allowing a cluster to be comprised of smaller free space extents. This part definitely adds some CPU time to the cluster allocations, but it allows the allocator to consume the small holes left behind by cow. Signed-off-by: Chris Mason <chris.mason@oracle.com>