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b4056afbd4
Bcache allocator initially has no free space to allocate. Firstly it does a garbage collection which is triggered by a cache device write and fills free space into ca->free[] lists. The discard happens after the free bucket is handled by garbage collection added into one of the ca->free[] lists. But normally this bucket will be allocated out very soon to requester and filled data onto it. The discard hint on this bucket LBA range doesn't help SSD control to improve internal erasure performance, and waste extra CPU cycles to issue discard bios. This patch removes the almost-useless discard code from alloc.c. Signed-off-by: Coly Li <colyli@fnnas.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.