diff options
Diffstat (limited to 'fs/ocfs2/localalloc.c')
| -rw-r--r-- | fs/ocfs2/localalloc.c | 114 |
1 files changed, 112 insertions, 2 deletions
diff --git a/fs/ocfs2/localalloc.c b/fs/ocfs2/localalloc.c index e39a3e7146c..00022aac2e8 100644 --- a/fs/ocfs2/localalloc.c +++ b/fs/ocfs2/localalloc.c @@ -75,10 +75,120 @@ static int ocfs2_local_alloc_new_window(struct ocfs2_super *osb, static int ocfs2_local_alloc_slide_window(struct ocfs2_super *osb, struct inode *local_alloc_inode); +/* + * ocfs2_la_default_mb() - determine a default size, in megabytes of + * the local alloc. + * + * Generally, we'd like to pick as large a local alloc as + * possible. Performance on large workloads tends to scale + * proportionally to la size. In addition to that, the reservations + * code functions more efficiently as it can reserve more windows for + * write. + * + * Some things work against us when trying to choose a large local alloc: + * + * - We need to ensure our sizing is picked to leave enough space in + * group descriptors for other allocations (such as block groups, + * etc). Picking default sizes which are a multiple of 4 could help + * - block groups are allocated in 2mb and 4mb chunks. + * + * - Likewise, we don't want to starve other nodes of bits on small + * file systems. This can easily be taken care of by limiting our + * default to a reasonable size (256M) on larger cluster sizes. + * + * - Some file systems can't support very large sizes - 4k and 8k in + * particular are limited to less than 128 and 256 megabytes respectively. + * + * The following reference table shows group descriptor and local + * alloc maximums at various cluster sizes (4k blocksize) + * + * csize: 4K group: 126M la: 121M + * csize: 8K group: 252M la: 243M + * csize: 16K group: 504M la: 486M + * csize: 32K group: 1008M la: 972M + * csize: 64K group: 2016M la: 1944M + * csize: 128K group: 4032M la: 3888M + * csize: 256K group: 8064M la: 7776M + * csize: 512K group: 16128M la: 15552M + * csize: 1024K group: 32256M la: 31104M + */ +#define OCFS2_LA_MAX_DEFAULT_MB 256 +#define OCFS2_LA_OLD_DEFAULT 8 +unsigned int ocfs2_la_default_mb(struct ocfs2_super *osb) +{ + unsigned int la_mb; + unsigned int gd_mb; + unsigned int megs_per_slot; + struct super_block *sb = osb->sb; + + gd_mb = ocfs2_clusters_to_megabytes(osb->sb, + 8 * ocfs2_group_bitmap_size(sb)); + + /* + * This takes care of files systems with very small group + * descriptors - 512 byte blocksize at cluster sizes lower + * than 16K and also 1k blocksize with 4k cluster size. + */ + if ((sb->s_blocksize == 512 && osb->s_clustersize <= 8192) + || (sb->s_blocksize == 1024 && osb->s_clustersize == 4096)) + return OCFS2_LA_OLD_DEFAULT; + + /* + * Leave enough room for some block groups and make the final + * value we work from a multiple of 4. + */ + gd_mb -= 16; + gd_mb &= 0xFFFFFFFB; + + la_mb = gd_mb; + + /* + * Keep window sizes down to a reasonable default + */ + if (la_mb > OCFS2_LA_MAX_DEFAULT_MB) { + /* + * Some clustersize / blocksize combinations will have + * given us a larger than OCFS2_LA_MAX_DEFAULT_MB + * default size, but get poor distribution when + * limited to exactly 256 megabytes. + * + * As an example, 16K clustersize at 4K blocksize + * gives us a cluster group size of 504M. Paring the + * local alloc size down to 256 however, would give us + * only one window and around 200MB left in the + * cluster group. Instead, find the first size below + * 256 which would give us an even distribution. + * + * Larger cluster group sizes actually work out pretty + * well when pared to 256, so we don't have to do this + * for any group that fits more than two + * OCFS2_LA_MAX_DEFAULT_MB windows. + */ + if (gd_mb > (2 * OCFS2_LA_MAX_DEFAULT_MB)) + la_mb = 256; + else { + unsigned int gd_mult = gd_mb; + + while (gd_mult > 256) + gd_mult = gd_mult >> 1; + + la_mb = gd_mult; + } + } + + megs_per_slot = osb->osb_clusters_at_boot / osb->max_slots; + megs_per_slot = ocfs2_clusters_to_megabytes(osb->sb, megs_per_slot); + /* Too many nodes, too few disk clusters. */ + if (megs_per_slot < la_mb) + la_mb = megs_per_slot; + + return la_mb; +} + void ocfs2_la_set_sizes(struct ocfs2_super *osb, int requested_mb) { struct super_block *sb = osb->sb; - unsigned int la_default_mb = OCFS2_DEFAULT_LOCAL_ALLOC_SIZE; + unsigned int la_default_mb = ocfs2_la_default_mb(osb); unsigned int la_max_mb; la_max_mb = ocfs2_clusters_to_megabytes(sb, @@ -185,7 +295,7 @@ int ocfs2_load_local_alloc(struct ocfs2_super *osb) osb->local_alloc_bits, (osb->bitmap_cpg - 1)); osb->local_alloc_bits = ocfs2_megabytes_to_clusters(osb->sb, - OCFS2_DEFAULT_LOCAL_ALLOC_SIZE); + ocfs2_la_default_mb(osb)); } /* read the alloc off disk */ |