mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-07 17:27:11 -04:00
9e779f3f24
For each bucket we track when the bucket became nonempty and when it became empty again: if we can ensure that there will be no journal flushes in the range [nonempty, empty) (possibly because they occured at the same journal sequence number), then it's safe to reuse the bucket without waiting for a journal commit. This is a major performance optimization for erasure coding, where writes are initially replicated, but the extra replicas are quickly dropped: if those buckets are reused and overwritten without issuing a cache flush to the underlying device, then they only cost bus bandwidth. But there's a tricky corner case when there's multiple empty -> nonempty -> empty transitions in quick succession, i.e. when data is getting overwritten immediately as it's being written. If this happens and the previous empty transition hasn't been flushed, we need to continue tracking the previous nonempty transition - not start a new one. Fixing this means we now need to track both the nonempty and empty transitions in bch_alloc_v4. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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.