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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.
Jianchao Wang
authored
Currently, kyber is very unfriendly with merging. kyber depends on ctx rq_list to do merging, however, most of time, it will not leave any requests in ctx rq_list. This is because even if tokens of one domain is used up, kyber will try to dispatch requests from other domain and flush the rq_list there. To improve this, we setup kyber_ctx_queue (kcq) which is similar with ctx, but it has rq_lists for different domain and build same mapping between kcq and khd as the ctx & hctx. Then we could merge, insert and dispatch for different domains separately. At the same time, only flush the rq_list of kcq when get domain token successfully. Then if one domain token is used up, the requests could be left in the rq_list of that domain and maybe merged with following io. Following is my test result on machine with 8 cores and NVMe card INTEL SSDPEKKR128G7 fio size=256m ioengine=libaio iodepth=64 direct=1 numjobs=8 seq/random +------+---------------------------------------------------------------+ |patch?| bw(MB/s) | iops | slat(usec) | clat(usec) | merge | +----------------------------------------------------------------------+ | w/o | 606/612 | 151k/153k | 6.89/7.03 | 3349.21/3305.40 | 0/0 | +----------------------------------------------------------------------+ | w/ | 1083/616 | 277k/154k | 4.93/6.95 | 1830.62/3279.95 | 223k/3k | +----------------------------------------------------------------------+ When set numjobs to 16, the bw and iops could reach 1662MB/s and 425k on my platform. Signed-off-by:Jianchao Wang <jianchao.w.wang@oracle.com> Tested-by:
Holger Hoffstätte <holger@applied-asynchrony.com> Reviewed-by:
Omar Sandoval <osandov@fb.com> Signed-off-by:
Jens Axboe <axboe@kernel.dk>
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