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Implement allocation size ranges and use for gang leaves (#17111)

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When forced to resort to ganging, ZFS currently allocates three child
blocks, each one third of the size of the original. This is true
regardless of whether larger allocations could be made, which would
allow us to have fewer gang leaves. This improves performance when
fragmentation is high enough to require ganging, but not so high that
all the free ranges are only just big enough to hold a third of the
recordsize. This is also useful for improving the behavior of a future
change to allow larger gang headers.

We add the ability for the allocation codepath to allocate a range of
sizes instead of a single fixed size. We then use this to pre-allocate
the DVAs for the gang children. If those allocations fail, we fall back
to the normal write path, which will likely re-gang.

Signed-off-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Co-authored-by: Paul Dagnelie <paul.dagnelie@klarasystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
This commit is contained in:
Paul Dagnelie
2025-05-02 15:32:18 -07:00
committed by GitHub
parent a7de203c86
commit 246e5883bb
24 changed files with 392 additions and 107 deletions
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module/zfs/vdev_raidz.c
+31 -3
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@@ -2235,6 +2235,33 @@ vdev_raidz_get_logical_width(vdev_raidz_t *vdrz, uint64_t txg)
mutex_exit(&vdrz->vd_expand_lock);
return (width);
}
/*
* This code converts an asize into the largest psize that can safely be written
* to an allocation of that size for this vdev.
*
* Note that this function will not take into account the effect of gang
* headers, which also modify the ASIZE of the DVAs. It is purely a reverse of
* the psize_to_asize function.
*/
static uint64_t
vdev_raidz_asize_to_psize(vdev_t *vd, uint64_t asize, uint64_t txg)
{
vdev_raidz_t *vdrz = vd->vdev_tsd;
uint64_t psize;
uint64_t ashift = vd->vdev_top->vdev_ashift;
uint64_t cols = vdrz->vd_original_width;
uint64_t nparity = vdrz->vd_nparity;
cols = vdev_raidz_get_logical_width(vdrz, txg);
ASSERT0(asize % (1 << ashift));
psize = (asize >> ashift);
psize -= nparity * DIV_ROUND_UP(psize, cols);
psize <<= ashift;
return (asize);
}
/*
* Note: If the RAIDZ vdev has been expanded, older BP's may have allocated
@@ -2245,7 +2272,7 @@ vdev_raidz_get_logical_width(vdev_raidz_t *vdrz, uint64_t txg)
* allocate P+1 sectors regardless of width ("cols", which is at least P+1).
*/
static uint64_t
vdev_raidz_asize(vdev_t *vd, uint64_t psize, uint64_t txg)
vdev_raidz_psize_to_asize(vdev_t *vd, uint64_t psize, uint64_t txg)
{
vdev_raidz_t *vdrz = vd->vdev_tsd;
uint64_t asize;
@@ -2309,7 +2336,7 @@ vdev_raidz_io_verify(zio_t *zio, raidz_map_t *rm, raidz_row_t *rr, int col)
zfs_range_seg64_t logical_rs, physical_rs, remain_rs;
logical_rs.rs_start = rr->rr_offset;
logical_rs.rs_end = logical_rs.rs_start +
vdev_raidz_asize(zio->io_vd, rr->rr_size,
vdev_raidz_psize_to_asize(zio->io_vd, rr->rr_size,
BP_GET_BIRTH(zio->io_bp));
raidz_col_t *rc = &rr->rr_col[col];
@@ -5093,7 +5120,8 @@ vdev_ops_t vdev_raidz_ops = {
.vdev_op_fini = vdev_raidz_fini,
.vdev_op_open = vdev_raidz_open,
.vdev_op_close = vdev_raidz_close,
.vdev_op_asize = vdev_raidz_asize,
.vdev_op_psize_to_asize = vdev_raidz_psize_to_asize,
.vdev_op_asize_to_psize = vdev_raidz_asize_to_psize,
.vdev_op_min_asize = vdev_raidz_min_asize,
.vdev_op_min_alloc = NULL,
.vdev_op_io_start = vdev_raidz_io_start,