b843786b0b
We've been noticing a trend of significant lock contention in the swap subsystem as core counts have been increasing in our fleet. It turns out that our swapfiles on btrfs on flash were in fact using the old swap code for rotational storage. This turns out to be a detection issue in the swapon sequence: btrfs sets si->bdev during swap activation, which currently happens *after* swapon's SSD detection and cluster setup. Thus, none of the SSD optimizations and cluster lock splitting are enabled for btrfs swap. Rearrange the swapon sequence so that filesystem activation happens *before* determining swap behavior based on the backing device. Afterwards, the nonrotational drive is detected correctly: - Adding 2097148k swap on /mnt/swapfile. Priority:-3 extents:1 across:2097148k + Adding 2097148k swap on /mnt/swapfile. Priority:-3 extents:1 across:2097148k SS Link: https://lkml.kernel.org/r/20240822112707.351844-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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.