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Div instructions show costly in profiles when the tx request header is set. Using right shift instead of a divide operation reduces the cycles spent in the function that sets the tx request header as shown in the profile. Use right shift operation instead. Profile before change: 43.24% 009 | |--23.41%-- user_sdma_send_pkts | | | |--99.90%-- hfi1_user_sdma_process_requestAfter: Profile after change: 45.75% 009 | |--14.81%-- user_sdma_send_pkts | | | |--99.95%-- hfi1_user_sdma_process_request Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com> Signed-off-by: Sebastian Sanchez <sebastian.sanchez@intel.com> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.