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This allows a list of requests to be issued, with the LLD only writing the hardware doorbell when necessary, after the last request was prepared. This is more efficient if we have lists of requests to issue, particularly on virtualized hardware, where writing the doorbell is more expensive than on real hardware. The use case for this is plugged IO, where blk-mq flushes a batch of requests all at once. The API is the same as for blk-mq, just with blk-mq concepts tweaked to fit the SCSI subsystem API: the "last" flag in blk_mq_queue_data becomes a flag in scsi_cmnd, while the queue_num in the commit_rqs callback is extracted from the hctx and passed as a parameter. The only complication is that blk-mq uses different plugging heuristics depending on whether commit_rqs is present or not. So we have two different sets of blk_mq_ops and pick one depending on whether the scsi_host template uses commit_rqs or not. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
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| 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 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.