7e170922f0
CR1_5 aims to optimize allocations which can't be satisfied in CR1. The fact that we couldn't find a group in CR1 suggests that it would be difficult to find a continuous extent to compleltely satisfy our allocations. So before falling to the slower CR2, in CR1.5 we proactively trim the the preallocations so we can find a group with (free / fragments) big enough. This speeds up our allocation at the cost of slightly reduced preallocation. The patch also adds a new sysfs tunable: * /sys/fs/ext4/<partition>/mb_cr1_5_max_trim_order This controls how much CR1.5 can trim a request before falling to CR2. For example, for a request of order 7 and max trim order 2, CR1.5 can trim this upto order 5. Suggested-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Link: https://lore.kernel.org/r/150fdf65c8e4cc4dba71e020ce0859bcf636a5ff.1685449706.git.ojaswin@linux.ibm.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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 Restructured Text 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.