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a75de82057
Allow multiple LTBs in the rxpool's ltb_set. The first n-1 LTBs will all be of the same size. The size of the last LTB in the set depends on the number of buffers and buffer (mtu) size. Having a set of LTBs per pool provides a couple of benefits. First, with the current value of IBMVNIC_MAX_LTB_SIZE of 16MB, with an MTU of 9000, we need a LTB (DMA buffer) of that size but the allocation can fail in low memory conditions. With a set of LTBs per pool, we can use several smaller (8MB) LTBs and hopefully have fewer allocation failures. (See also comments in ibmvnic.h on the trade-off with smaller LTBs) Second since the kernel limits the size of the DMA buffer to 16MB (based on MAX_ORDER), with a single DMA buffer per pool, the pool is also limited to 16MB. This in turn limits the number of buffers per pool to 1763 when MTU is 9000. With a set of LTBs per pool, we can have upto the max of 4096 buffers per pool even when MTU is 9000. Suggested-by: Brian King <brking@linux.ibm.com> Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com> Signed-off-by: Dany Madden <drt@linux.ibm.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
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There are various text files in the Documentation/ subdirectory,
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