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MFV r319742: 8056 zfs send size estimate is inaccurate for some zvols

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illumos/illumos-gate@0255edcc85
0255edcc85

https://www.illumos.org/issues/8056
  The send size estimate for a zvol can be too low, if the size of the record
  headers (dmu_replay_record_t's) is a significant portion of the size.
  This is typically the case when the data is highly compressible, especially
  with embedded blocks.
  The problem is that dmu_adjust_send_estimate_for_indirects() assumes that
  blocks are the size of the "recordsize" property (128KB).
  However, for zvols, the blocks are the size of the "volblocksize" property
  (8KB). Therefore, we estimate that there will be 16x less record headers than
  there really will be.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Paul Dagnelie <pcd@delphix.com>

MFC after:	3 weeks
This commit is contained in:
Andriy Gapon 2017-06-22 16:58:09 +00:00
commit ae5ec64b88
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=320238
1 changed files with 13 additions and 2 deletions
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15
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_send.c
View File

@ -1140,10 +1140,17 @@ dmu_adjust_send_estimate_for_indirects(dsl_dataset_t *ds, uint64_t uncompressed,
*/
uint64_t recordsize;
uint64_t record_count;
objset_t *os;
VERIFY0(dmu_objset_from_ds(ds, &os));
/* Assume all (uncompressed) blocks are recordsize. */
err = dsl_prop_get_int_ds(ds, zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
&recordsize);
if (os->os_phys->os_type == DMU_OST_ZVOL) {
err = dsl_prop_get_int_ds(ds,
zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &recordsize);
} else {
err = dsl_prop_get_int_ds(ds,
zfs_prop_to_name(ZFS_PROP_RECORDSIZE), &recordsize);
}
if (err != 0)
return (err);
record_count = uncompressed / recordsize;
@ -1212,6 +1219,10 @@ dmu_send_estimate(dsl_dataset_t *ds, dsl_dataset_t *fromds,
err = dmu_adjust_send_estimate_for_indirects(ds, uncomp, comp,
stream_compressed, sizep);
/*
* Add the size of the BEGIN and END records to the estimate.
*/
*sizep += 2 * sizeof (dmu_replay_record_t);
return (err);
}