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ublk_drv currently creates block devices with the default max_segments and max_segment_size limits of BLK_MAX_SEGMENTS (128) and BLK_MAX_SEGMENT_SIZE (65536) respectively. These defaults can artificially constrain the I/O size seen by the ublk server - for example, suppose that the ublk server has configured itself to accept I/Os up to 1M and the application is also issuing 1M sized I/Os. If the I/O buffer used by the application is backed by 4K pages, the buffer could consist of up to 1M / 4K = 256 physically discontiguous segments (even if the buffer is virtually contiguous). As such, the I/O could exceed the default max_segments limit and get split. This can cause unnecessary performance issues if the ublk server is optimized to handle 1M I/Os. The block layer's segment count/size limits exist to model hardware constraints which don't exist in ublk_drv's case, so just remove those limits for the block devices created by ublk_drv. Signed-off-by: Uday Shankar <ushankar@purestorage.com> Reviewed-by: Riley Thomasson <riley@purestorage.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20240430211623.2802036-1-ushankar@purestorage.com Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.