diff options
| -rw-r--r-- | module/zfs/metaslab.c | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c index 7ff1a4f5a..86bf3c197 100644 --- a/module/zfs/metaslab.c +++ b/module/zfs/metaslab.c @@ -2335,28 +2335,42 @@ top: * figure out whether the corresponding vdev is * over- or under-used relative to the pool, * and set an allocation bias to even it out. + * + * Bias is also used to compensate for unequally + * sized vdevs so that space is allocated fairly. */ if (mc->mc_aliquot == 0 && metaslab_bias_enabled) { vdev_stat_t *vs = &vd->vdev_stat; - int64_t vu, cu; - - vu = (vs->vs_alloc * 100) / (vs->vs_space + 1); - cu = (mc->mc_alloc * 100) / (mc->mc_space + 1); + int64_t vs_free = vs->vs_space - vs->vs_alloc; + int64_t mc_free = mc->mc_space - mc->mc_alloc; + int64_t ratio; /* * Calculate how much more or less we should * try to allocate from this device during * this iteration around the rotor. - * For example, if a device is 80% full - * and the pool is 20% full then we should - * reduce allocations by 60% on this device. * - * mg_bias = (20 - 80) * 512K / 100 = -307K + * This basically introduces a zero-centered + * bias towards the devices with the most + * free space, while compensating for vdev + * size differences. + * + * Examples: + * vdev V1 = 16M/128M + * vdev V2 = 16M/128M + * ratio(V1) = 100% ratio(V2) = 100% + * + * vdev V1 = 16M/128M + * vdev V2 = 64M/128M + * ratio(V1) = 127% ratio(V2) = 72% * - * This reduces allocations by 307K for this - * iteration. + * vdev V1 = 16M/128M + * vdev V2 = 64M/512M + * ratio(V1) = 40% ratio(V2) = 160% */ - mg->mg_bias = ((cu - vu) * + ratio = (vs_free * mc->mc_alloc_groups * 100) / + (mc_free + 1); + mg->mg_bias = ((ratio - 100) * (int64_t)mg->mg_aliquot) / 100; } else if (!metaslab_bias_enabled) { mg->mg_bias = 0; |