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Improve mg_aliquot math 

When calculating mg_aliquot alike to #12046 use number of unique data
disks in the vdev, not the total number of children vdev.  Increase
default value of the tunable from 512KB to 1MB to compensate.

Before this change each disk in striped pool was getting 512KB of
sequential data, in 2-wide mirror -- 1MB, in 3-wide RAIDZ1 -- 768KB.
After this change in all the cases each disk should get 1MB.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored-By: iXsystems, Inc.
Closes #13388
This commit is contained in:
Alexander Motin 2022-05-04 14:33:42 -04:00 committed by Brian Behlendorf
parent dd9c110ab5
commit 6e1e90d64c
2 changed files with 8 additions and 7 deletions
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6
man/man4/zfs.4
View File

@ -213,12 +213,12 @@ For L2ARC devices less than 1GB, the amount of data
evicts is significant compared to the amount of restored L2ARC data.
In this case, do not write log blocks in L2ARC in order not to waste space.
.
.It Sy metaslab_aliquot Ns = Ns Sy 524288 Ns B Po 512kB Pc Pq ulong
.It Sy metaslab_aliquot Ns = Ns Sy 1048576 Ns B Po 1MB Pc Pq ulong
Metaslab granularity, in bytes.
This is roughly similar to what would be referred to as the "stripe size"
in traditional RAID arrays.
In normal operation, ZFS will try to write this amount of data
to a top-level vdev before moving on to the next one.
In normal operation, ZFS will try to write this amount of data to each disk
before moving on to the next top-level vdev.
.
.It Sy metaslab_bias_enabled Ns = Ns Sy 1 Ns | Ns 0 Pq int
Enable metaslab group biasing based on their vdevs' over- or under-utilization

9
module/zfs/metaslab.c
View File

@ -48,10 +48,10 @@
/*
* Metaslab granularity, in bytes. This is roughly similar to what would be
* referred to as the "stripe size" in traditional RAID arrays. In normal
* operation, we will try to write this amount of data to a top-level vdev
* before moving on to the next one.
* operation, we will try to write this amount of data to each disk before
* moving on to the next top-level vdev.
*/
unsigned long metaslab_aliquot = 512 << 10;
static unsigned long metaslab_aliquot = 1024 * 1024;
/*
* For testing, make some blocks above a certain size be gang blocks.
@ -899,7 +899,8 @@ metaslab_group_activate(metaslab_group_t *mg)
if (++mg->mg_activation_count <= 0)
return;
mg->mg_aliquot = metaslab_aliquot * MAX(1, mg->mg_vd->vdev_children);
mg->mg_aliquot = metaslab_aliquot * MAX(1,
vdev_get_ndisks(mg->mg_vd) - vdev_get_nparity(mg->mg_vd));
metaslab_group_alloc_update(mg);
if ((mgprev = mc->mc_allocator[0].mca_rotor) == NULL) {