On 20/01/2015 15:09, Alexander Motin wrote:
> Author: mav
> Date: Tue Jan 20 13:09:12 2015
> New Revision: 277419
> URL: https://svnweb.freebsd.org/changeset/base/277419
>
> Log:
> Allow skipping dmu_buf_will_dirty() call in dsl_dir_transfer_space().
>
> dsl_dir_transfer_space() is mostly called after dsl_dir_diduse_space(),
> which already calls dmu_buf_will_dirty() for the same dbuf and tx, so
> its duplicate call in those cases will change nothing, only spend time.
>
> Skipping this call by four times reduces time spent in dbuf_write_done()
> and descendants, updating dataset statistics with several congested lock
> acquisitions. When rewriting 8K zvol blocks at 1GB/s rate, this reduces
> CPU time spent inside dbuf_write_done(), according to profiling, from 45%
> of 683K samples to 18% of 422K.
It probably would make sense to discuss such a change with the upstream
folks. Or, at the very least, let them know about it.
> MFC after: 2 weeks
>
> Modified:
> head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
> head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c
>
> Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
> ==============================================================================
> --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c Tue Jan
> 20 12:28:24 2015 (r277418)
> +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c Tue Jan
> 20 13:09:12 2015 (r277419)
> @@ -136,7 +136,7 @@ dsl_dataset_block_born(dsl_dataset_t *ds
> dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD, delta,
> compressed, uncompressed, tx);
> dsl_dir_transfer_space(ds->ds_dir, used - delta,
> - DD_USED_REFRSRV, DD_USED_HEAD, tx);
> + DD_USED_REFRSRV, DD_USED_HEAD, NULL);
> }
>
> int
> @@ -179,7 +179,7 @@ dsl_dataset_block_kill(dsl_dataset_t *ds
> dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD,
> delta, -compressed, -uncompressed, tx);
> dsl_dir_transfer_space(ds->ds_dir, -used - delta,
> - DD_USED_REFRSRV, DD_USED_HEAD, tx);
> + DD_USED_REFRSRV, DD_USED_HEAD, NULL);
> } else {
> dprintf_bp(bp, "putting on dead list: %s", "");
> if (async) {
> @@ -2837,7 +2837,7 @@ dsl_dataset_clone_swap_sync_impl(dsl_dat
> origin_head->ds_dir->dd_origin_txg, UINT64_MAX,
> &odl_used, &odl_comp, &odl_uncomp);
> dsl_dir_transfer_space(origin_head->ds_dir, cdl_used - odl_used,
> - DD_USED_HEAD, DD_USED_SNAP, tx);
> + DD_USED_HEAD, DD_USED_SNAP, NULL);
> }
>
> /* swap ds_*_bytes */
>
> Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c
> ==============================================================================
> --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c Tue Jan
> 20 12:28:24 2015 (r277418)
> +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dir.c Tue Jan
> 20 13:09:12 2015 (r277419)
> @@ -1389,7 +1389,7 @@ dsl_dir_diduse_space(dsl_dir_t *dd, dd_u
> accounted_delta, compressed, uncompressed, tx);
> dsl_dir_transfer_space(dd->dd_parent,
> used - accounted_delta,
> - DD_USED_CHILD_RSRV, DD_USED_CHILD, tx);
> + DD_USED_CHILD_RSRV, DD_USED_CHILD, NULL);
> }
> }
>
> @@ -1397,7 +1397,7 @@ void
> dsl_dir_transfer_space(dsl_dir_t *dd, int64_t delta,
> dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx)
> {
> - ASSERT(dmu_tx_is_syncing(tx));
> + ASSERT(tx == NULL || dmu_tx_is_syncing(tx));
> ASSERT(oldtype < DD_USED_NUM);
> ASSERT(newtype < DD_USED_NUM);
>
> @@ -1405,7 +1405,8 @@ dsl_dir_transfer_space(dsl_dir_t *dd, in
> !(dsl_dir_phys(dd)->dd_flags & DD_FLAG_USED_BREAKDOWN))
> return;
>
> - dmu_buf_will_dirty(dd->dd_dbuf, tx);
> + if (tx != NULL)
> + dmu_buf_will_dirty(dd->dd_dbuf, tx);
> mutex_enter(&dd->dd_lock);
> ASSERT(delta > 0 ?
> dsl_dir_phys(dd)->dd_used_breakdown[oldtype] >= delta :
>
--
Andriy Gapon
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