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If the last bvec of the 1st bio and the 1st bvec of the next bio are physically contigious, and the latter can be merged to last segment of the 1st bio, we should think they don't violate sg gap(or virt boundary) limit. Both Vitaly and Dexuan reported lots of unmergeable small bios are observed when running mkfs on Hyper-V virtual storage, and performance becomes quite low. This patch fixes that performance issue. The same issue should exist on NVMe, since it sets virt boundary too. Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com> Reported-by: Dexuan Cui <decui@microsoft.com> Tested-by: Dexuan Cui <decui@microsoft.com> Cc: Keith Busch <keith.busch@intel.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.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.