eba1469f8f
We always allocate a delayed extent op structure when allocating a tree block (except for log trees), but most of the time we don't need it as we only need to set the BTRFS_BLOCK_FLAG_FULL_BACKREF if we're dealing with a relocation tree and we only need to set the key of a tree block in a btrfs_tree_block_info structure if we are not using skinny metadata (feature enabled by default since btrfs-progs 3.18 and available as of kernel 3.10). In these cases, where we don't need neither to update flags nor to set the key, we only use the delayed extent op structure to set the tree block's level. This is a waste of memory and besides that, the memory allocation can fail and can add additional latency. Instead of using a delayed extent op structure to store the level of the tree block, use the delayed ref head to store it. This doesn't change the size of neither structure and helps us avoid allocating delayed extent ops structures when using the skinny metadata feature and there's no relocation going on. This also gets rid of a BUG_ON(). For example, for a fs_mark run, with 5 iterations, 8 threads and 100K files per iteration, before this patch there were 118109 allocations of delayed extent op structures and after it there were none. Reviewed-by: Boris Burkov <boris@bur.io> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.