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cee1b21523
This will enable changing the virtual boundary of null blk devices. For now, null blk devices didn't have any restriction on the scatter/gather elements received from the block layer. Add a module parameter and a configfs option that will control the virtual boundary. This will enable testing the efficiency of the block layer bounce buffer in case a suitable application will send discontiguous IO to the given device. Initial testing with patched FIO showed the following results (64 jobs, 128 iodepth, 1 nullb device): IO size READ (virt=false) READ (virt=true) Write (virt=false) Write (virt=true) ---------- ------------------- ----------------- ------------------- ------------------- 1k 10.7M 8482k 10.8M 8471k 2k 10.4M 8266k 10.4M 8271k 4k 10.4M 8274k 10.3M 8226k 8k 10.2M 8131k 9800k 7933k 16k 9567k 7764k 8081k 6828k 32k 8865k 7309k 5570k 5153k 64k 7695k 6586k 2682k 2617k 128k 5346k 5489k 1320k 1296k Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Link: https://lore.kernel.org/r/20210412095523.278632-1-mgurtovoy@nvidia.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 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.