diff options
| -rw-r--r-- | usr/src/uts/common/fs/zfs/vdev.c | 75 |
1 files changed, 50 insertions, 25 deletions
diff --git a/usr/src/uts/common/fs/zfs/vdev.c b/usr/src/uts/common/fs/zfs/vdev.c index 6fee8109e0..db2d12db96 100644 --- a/usr/src/uts/common/fs/zfs/vdev.c +++ b/usr/src/uts/common/fs/zfs/vdev.c @@ -72,15 +72,21 @@ static vdev_ops_t *vdev_ops_table[] = { /* maximum scrub/resilver I/O queue per leaf vdev */ int zfs_scrub_limit = 10; -/* maximum number of metaslabs per top-level vdev */ +/* target number of metaslabs per top-level vdev */ int vdev_max_ms_count = 200; -/* minimum amount of metaslabs per top-level vdev */ +/* minimum number of metaslabs per top-level vdev */ int vdev_min_ms_count = 16; -/* see comment in vdev_metaslab_set_size() */ +/* practical upper limit of total metaslabs per top-level vdev */ +int vdev_ms_count_limit = 1ULL << 17; + +/* lower limit for metaslab size (512M) */ int vdev_default_ms_shift = 29; +/* upper limit for metaslab size (256G) */ +int vdev_max_ms_shift = 38; + boolean_t vdev_validate_skip = B_FALSE; /* @@ -2028,34 +2034,53 @@ void vdev_metaslab_set_size(vdev_t *vd) { uint64_t asize = vd->vdev_asize; - uint64_t ms_shift = 0; + uint64_t ms_count = asize >> vdev_default_ms_shift; + uint64_t ms_shift; /* - * For vdevs that are bigger than 8G the metaslab size varies in - * a way that the number of metaslabs increases in powers of two, - * linearly in terms of vdev_asize, starting from 16 metaslabs. - * So for vdev_asize of 8G we get 16 metaslabs, for 16G, we get 32, - * and so on, until we hit the maximum metaslab count limit - * [vdev_max_ms_count] from which point the metaslab count stays - * the same. + * There are two dimensions to the metaslab sizing calculation: + * the size of the metaslab and the count of metaslabs per vdev. + * In general, we aim for vdev_max_ms_count (200) metaslabs. The + * range of the dimensions are as follows: + * + * 2^29 <= ms_size <= 2^38 + * 16 <= ms_count <= 131,072 + * + * On the lower end of vdev sizes, we aim for metaslabs sizes of + * at least 512MB (2^29) to minimize fragmentation effects when + * testing with smaller devices. However, the count constraint + * of at least 16 metaslabs will override this minimum size goal. + * + * On the upper end of vdev sizes, we aim for a maximum metaslab + * size of 256GB. However, we will cap the total count to 2^17 + * metaslabs to keep our memory footprint in check. + * + * The net effect of applying above constrains is summarized below. + * + * vdev size metaslab count + * -------------|----------------- + * < 8GB ~16 + * 8GB - 100GB one per 512MB + * 100GB - 50TB ~200 + * 50TB - 32PB one per 256GB + * > 32PB ~131,072 + * ------------------------------- */ - ms_shift = vdev_default_ms_shift; - if ((asize >> ms_shift) < vdev_min_ms_count) { - /* - * For devices that are less than 8G we want to have - * exactly 16 metaslabs. We don't want less as integer - * division rounds down, so less metaslabs mean more - * wasted space. We don't want more as these vdevs are - * small and in the likely event that we are running - * out of space, the SPA will have a hard time finding - * space due to fragmentation. - */ + if (ms_count < vdev_min_ms_count) ms_shift = highbit64(asize / vdev_min_ms_count); - ms_shift = MAX(ms_shift, SPA_MAXBLOCKSHIFT); - - } else if ((asize >> ms_shift) > vdev_max_ms_count) { + else if (ms_count > vdev_max_ms_count) ms_shift = highbit64(asize / vdev_max_ms_count); + else + ms_shift = vdev_default_ms_shift; + + if (ms_shift < SPA_MAXBLOCKSHIFT) { + ms_shift = SPA_MAXBLOCKSHIFT; + } else if (ms_shift > vdev_max_ms_shift) { + ms_shift = vdev_max_ms_shift; + /* cap the total count to constrain memory footprint */ + if ((asize >> ms_shift) > vdev_ms_count_limit) + ms_shift = highbit64(asize / vdev_ms_count_limit); } vd->vdev_ms_shift = ms_shift; |