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Replace hand-crafted naive byte-by-byte zero block detection routine

Description

Replace hand-crafted naive byte-by-byte zero block detection routine
with macro based around memcmp(). The latter is expected to be some
8 times faster on a modern 64-bit architectures.

In practice, throughput of doing conv=sparse from /dev/zero to /dev/null
went up some 5-fold here from 1.9GB/sec to 9.7GB/sec with this change
(bs=128k).

MFC after: 2 weeks

Details

Committed
sobomaxNov 29 2018, 7:28 PM
Parents
rS341256: If BENEATH is specified, always latch the topping directory vnode.
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