92524fa123
scsi_mq_setup_tags() currently preallocates a big buffer for protection SGL entries. scsi_mq_sgl_size() is used to determine the size for both data and protection information scatterlists but the protection buffer is usually much smaller. For example, one 512-byte sector needs 8 bytes of protection information. Given that the maximum number of sectors for one request is 2560 (BLK_DEF_MAX_SECTORS) sectors, the max protection information buffer size is just 20K. The protection information segment count generally matches the number of bios in the request. As a result, the typical actual number of segments won't be very big. And should the need arise, allocating a bigger SGL from slab is fast enough. Pre-allocate only one SGL entry for protection information and switch to runtime allocation in case that the protection information segment number is bigger than 1. This reduces memory tied up by static command allocations. For example, 500+ MB is saved on single lpfc HBA. [mkp: attempted to clarify commit desc] Cc: Christoph Hellwig <hch@lst.de> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Ewan D. Milne <emilne@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.