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Gang ABD Type

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Adding the gang ABD type, which allows for linear and scatter ABDs to
be chained together into a single ABD.

This can be used to avoid doing memory copies to/from ABDs. An example
of this can be found in vdev_queue.c in the vdev_queue_aggregate()
function.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Brian <bwa@clemson.edu>
Co-authored-by: Mark Maybee <mmaybee@cray.com>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #10069
This commit is contained in:
Brian Atkinson
2020-05-20 19:06:09 -06:00
committed by GitHub
parent 501a1511ae
commit fb822260b1
7 changed files with 629 additions and 106 deletions
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module/os/freebsd/zfs/abd_os.c
+61 -1
View File
@@ -90,6 +90,15 @@ SYSCTL_ULONG(_vfs_zfs, OID_AUTO, abd_chunk_size, CTLFLAG_RDTUN,
kmem_cache_t *abd_chunk_cache;
static kstat_t *abd_ksp;
/*
* We use a scattered SPA_MAXBLOCKSIZE sized ABD whose chunks are
* just a single zero'd sized zfs_abd_chunk_size buffer. This
* allows us to conserve memory by only using a single zero buffer
* for the scatter chunks.
*/
abd_t *abd_zero_scatter = NULL;
static char *abd_zero_buf = NULL;
static void
abd_free_chunk(void *c)
{
@@ -193,6 +202,8 @@ abd_alloc_struct(size_t size)
abd_u.abd_scatter.abd_chunks[chunkcnt]);
abd_t *abd = kmem_alloc(abd_size, KM_PUSHPAGE);
ASSERT3P(abd, !=, NULL);
list_link_init(&abd->abd_gang_link);
mutex_init(&abd->abd_mtx, NULL, MUTEX_DEFAULT, NULL);
ABDSTAT_INCR(abdstat_struct_size, abd_size);
return (abd);
@@ -203,10 +214,53 @@ abd_free_struct(abd_t *abd)
{
size_t chunkcnt = abd_is_linear(abd) ? 0 : abd_scatter_chunkcnt(abd);
int size = offsetof(abd_t, abd_u.abd_scatter.abd_chunks[chunkcnt]);
mutex_destroy(&abd->abd_mtx);
ASSERT(!list_link_active(&abd->abd_gang_link));
kmem_free(abd, size);
ABDSTAT_INCR(abdstat_struct_size, -size);
}
/*
* Allocate scatter ABD of size SPA_MAXBLOCKSIZE, where
* each chunk in the scatterlist will be set to abd_zero_buf.
*/
static void
abd_alloc_zero_scatter(void)
{
size_t n = abd_chunkcnt_for_bytes(SPA_MAXBLOCKSIZE);
abd_zero_buf = kmem_zalloc(zfs_abd_chunk_size, KM_SLEEP);
abd_zero_scatter = abd_alloc_struct(SPA_MAXBLOCKSIZE);
abd_zero_scatter->abd_flags = ABD_FLAG_OWNER | ABD_FLAG_ZEROS;
abd_zero_scatter->abd_size = SPA_MAXBLOCKSIZE;
abd_zero_scatter->abd_parent = NULL;
zfs_refcount_create(&abd_zero_scatter->abd_children);
ABD_SCATTER(abd_zero_scatter).abd_offset = 0;
ABD_SCATTER(abd_zero_scatter).abd_chunk_size =
zfs_abd_chunk_size;
for (int i = 0; i < n; i++) {
ABD_SCATTER(abd_zero_scatter).abd_chunks[i] =
abd_zero_buf;
}
ABDSTAT_BUMP(abdstat_scatter_cnt);
ABDSTAT_INCR(abdstat_scatter_data_size, zfs_abd_chunk_size);
}
static void
abd_free_zero_scatter(void)
{
zfs_refcount_destroy(&abd_zero_scatter->abd_children);
ABDSTAT_BUMPDOWN(abdstat_scatter_cnt);
ABDSTAT_INCR(abdstat_scatter_data_size, -(int)zfs_abd_chunk_size);
abd_free_struct(abd_zero_scatter);
abd_zero_scatter = NULL;
kmem_free(abd_zero_buf, zfs_abd_chunk_size);
}
void
abd_init(void)
{
@@ -219,11 +273,15 @@ abd_init(void)
abd_ksp->ks_data = &abd_stats;
kstat_install(abd_ksp);
}
abd_alloc_zero_scatter();
}
void
abd_fini(void)
{
abd_free_zero_scatter();
if (abd_ksp != NULL) {
kstat_delete(abd_ksp);
abd_ksp = NULL;
@@ -271,12 +329,13 @@ abd_alloc_scatter_offset_chunkcnt(size_t chunkcnt)
abd_u.abd_scatter.abd_chunks[chunkcnt]);
abd_t *abd = kmem_alloc(abd_size, KM_PUSHPAGE);
ASSERT3P(abd, !=, NULL);
list_link_init(&abd->abd_gang_link);
mutex_init(&abd->abd_mtx, NULL, MUTEX_DEFAULT, NULL);
ABDSTAT_INCR(abdstat_struct_size, abd_size);
return (abd);
}
abd_t *
abd_get_offset_scatter(abd_t *sabd, size_t off)
{
@@ -332,6 +391,7 @@ abd_iter_scatter_chunk_index(struct abd_iter *aiter)
void
abd_iter_init(struct abd_iter *aiter, abd_t *abd)
{
ASSERT(!abd_is_gang(abd));
abd_verify(abd);
aiter->iter_abd = abd;
aiter->iter_pos = 0;