blackbird-op-linux - Blackbird™ Linux sources for OpenPOWER

	Commit message (Collapse)	Author	Age	Files	Lines
*	arm64: csum: Fix pathological zero-length calls	Robin Murphy	2020-01-17	1	-0/+3
\| \| \| \| \| \| \| \| \| \| \| \| \|	In validating the checksumming results of the new routine, I sadly neglected to test its not-checksumming results. Thus it slipped through that the one case where @buff is already dword-aligned and @len = 0 manages to defeat the tail-masking logic and behave as if @len = 8. For a zero length it doesn't make much sense to deference @buff anyway, so just add an early return (which has essentially zero impact on performance). Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
*	arm64: Implement optimised checksum routine	Robin Murphy	2020-01-16	1	-0/+123
	Apparently there exist certain workloads which rely heavily on software checksumming, for which the generic do_csum() implementation becomes a significant bottleneck. Therefore let's give arm64 its own optimised version - for ease of maintenance this foregoes assembly or intrisics, and is thus not actually arm64-specific, but does rely heavily on C idioms that translate well to the A64 ISA and the typical load/store capabilities of most ARMv8 CPU cores. The resulting increase in checksum throughput scales nicely with buffer size, tending towards 4x for a small in-order core (Cortex-A53), and up to 6x or more for an aggressive big core (Ampere eMAG). Reported-by: Lingyan Huang <huanglingyan2@huawei.com> Tested-by: Lingyan Huang <huanglingyan2@huawei.com> Signed-off-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Will Deacon <will@kernel.org>