Matthew Ahrens e2af2acce3 allow callers to allocate and provide the abd_t struct ... The `abd_get_offset_*()` routines create an abd_t that references another abd_t, and doesn't allocate any pages/buffers of its own. In some workloads, these routines may be called frequently, to create many abd_t's representing small pieces of a single large abd_t. In particular, the upcoming RAIDZ Expansion project makes heavy use of these routines. This commit adds the ability for the caller to allocate and provide the abd_t struct to a variant of `abd_get_offset_*()`. This eliminates the cost of allocating the abd_t and performing the accounting associated with it (`abdstat_struct_size`). The RAIDZ/DRAID code uses this for the `rc_abd`, which references the zio's abd. The upcoming RAIDZ Expansion project will leverage this infrastructure to increase performance of reads post-expansion by around 50%. Additionally, some of the interfaces around creating and destroying abd_t's are cleaned up. Most significantly, the distinction between `abd_put()` and `abd_free()` is eliminated; all types of abd_t's are now disposed of with `abd_free()`. Reviewed-by: Brian Atkinson <batkinson@lanl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Issue #8853 Closes #11439		2021-01-20 11:24:37 -08:00
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spl	FreeBSD: Skip RAW kstat sysctls by default	2020-10-26 14:34:28 -07:00
zfs	allow callers to allocate and provide the abd_t struct	2021-01-20 11:24:37 -08:00