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allow callers to allocate and provide the abd_t struct

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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
This commit is contained in:
Matthew Ahrens
2021-01-20 11:24:37 -08:00
committed by GitHub
parent 03f036cbcc
commit e2af2acce3
16 changed files with 261 additions and 295 deletions
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include/sys/abd_impl.h
+5 -43
View File
@@ -32,51 +32,11 @@
extern "C" {
#endif
typedef enum abd_flags {
ABD_FLAG_LINEAR = 1 << 0, /* is buffer linear (or scattered)? */
ABD_FLAG_OWNER = 1 << 1, /* does it own its data buffers? */
ABD_FLAG_META = 1 << 2, /* does this represent FS metadata? */
ABD_FLAG_MULTI_ZONE = 1 << 3, /* pages split over memory zones */
ABD_FLAG_MULTI_CHUNK = 1 << 4, /* pages split over multiple chunks */
ABD_FLAG_LINEAR_PAGE = 1 << 5, /* linear but allocd from page */
ABD_FLAG_GANG = 1 << 6, /* mult ABDs chained together */
ABD_FLAG_GANG_FREE = 1 << 7, /* gang ABD is responsible for mem */
ABD_FLAG_ZEROS = 1 << 8, /* ABD for zero-filled buffer */
} abd_flags_t;
typedef enum abd_stats_op {
ABDSTAT_INCR, /* Increase abdstat values */
ABDSTAT_DECR /* Decrease abdstat values */
} abd_stats_op_t;
struct abd {
abd_flags_t abd_flags;
uint_t abd_size; /* excludes scattered abd_offset */
list_node_t abd_gang_link;
struct abd *abd_parent;
zfs_refcount_t abd_children;
kmutex_t abd_mtx;
union {
struct abd_scatter {
uint_t abd_offset;
#if defined(__FreeBSD__) && defined(_KERNEL)
uint_t abd_chunk_size;
void *abd_chunks[];
#else
uint_t abd_nents;
struct scatterlist *abd_sgl;
#endif
} abd_scatter;
struct abd_linear {
void *abd_buf;
struct scatterlist *abd_sgl; /* for LINEAR_PAGE */
} abd_linear;
struct abd_gang {
list_t abd_gang_chain;
} abd_gang;
} abd_u;
};
struct scatterlist; /* forward declaration */
struct abd_iter {
@@ -95,14 +55,16 @@ struct abd_iter {
extern abd_t *abd_zero_scatter;
abd_t *abd_gang_get_offset(abd_t *, size_t *);
abd_t *abd_alloc_struct(size_t);
void abd_free_struct(abd_t *);
/*
* OS specific functions
*/
abd_t *abd_alloc_struct(size_t);
abd_t *abd_get_offset_scatter(abd_t *, size_t);
void abd_free_struct(abd_t *);
abd_t *abd_alloc_struct_impl(size_t);
abd_t *abd_get_offset_scatter(abd_t *, abd_t *, size_t);
void abd_free_struct_impl(abd_t *);
void abd_alloc_chunks(abd_t *, size_t);
void abd_free_chunks(abd_t *);
boolean_t abd_size_alloc_linear(size_t);