iser-target: Skip data copy if all the command data comes as immediate
Given that supporting zcopy immediate data for all IOs requires iser driver to use its own buffer allocations, we settle with avoiding data copy for IOs with data length of up to 8K (which is more latency sensitive anyway). This trims IO write latency by up to 3us and increase IOPs by up to 40% by saving CPU time doing sg_copy_from_buffer (8K IO size is the obvious winner here). Signed-off-by: Jenny Derzhavetz <jennyf@mellanox.com> Signed-off-by: Sagi Grimberg <sagig@mellanox.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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