diff options
Diffstat (limited to 'fs/xfs/libxfs/xfs_alloc.c')
| -rw-r--r-- | fs/xfs/libxfs/xfs_alloc.c | 154 |
1 files changed, 142 insertions, 12 deletions
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 8191301a9039..925eba9489d5 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -716,6 +716,7 @@ struct xfs_alloc_cur { struct xfs_btree_cur *cnt; /* btree cursors */ struct xfs_btree_cur *bnolt; struct xfs_btree_cur *bnogt; + xfs_extlen_t cur_len;/* current search length */ xfs_agblock_t rec_bno;/* extent startblock */ xfs_extlen_t rec_len;/* extent length */ xfs_agblock_t bno; /* alloc bno */ @@ -740,6 +741,7 @@ xfs_alloc_cur_setup( ASSERT(args->alignment == 1 || args->type != XFS_ALLOCTYPE_THIS_BNO); + acur->cur_len = args->maxlen; acur->rec_bno = 0; acur->rec_len = 0; acur->bno = 0; @@ -921,6 +923,76 @@ xfs_alloc_cur_finish( } /* + * Locality allocation lookup algorithm. This expects a cntbt cursor and uses + * bno optimized lookup to search for extents with ideal size and locality. + */ +STATIC int +xfs_alloc_cntbt_iter( + struct xfs_alloc_arg *args, + struct xfs_alloc_cur *acur) +{ + struct xfs_btree_cur *cur = acur->cnt; + xfs_agblock_t bno; + xfs_extlen_t len, cur_len; + int error; + int i; + + if (!xfs_alloc_cur_active(cur)) + return 0; + + /* locality optimized lookup */ + cur_len = acur->cur_len; + error = xfs_alloc_lookup_ge(cur, args->agbno, cur_len, &i); + if (error) + return error; + if (i == 0) + return 0; + error = xfs_alloc_get_rec(cur, &bno, &len, &i); + if (error) + return error; + + /* check the current record and update search length from it */ + error = xfs_alloc_cur_check(args, acur, cur, &i); + if (error) + return error; + ASSERT(len >= acur->cur_len); + acur->cur_len = len; + + /* + * We looked up the first record >= [agbno, len] above. The agbno is a + * secondary key and so the current record may lie just before or after + * agbno. If it is past agbno, check the previous record too so long as + * the length matches as it may be closer. Don't check a smaller record + * because that could deactivate our cursor. + */ + if (bno > args->agbno) { + error = xfs_btree_decrement(cur, 0, &i); + if (!error && i) { + error = xfs_alloc_get_rec(cur, &bno, &len, &i); + if (!error && i && len == acur->cur_len) + error = xfs_alloc_cur_check(args, acur, cur, + &i); + } + if (error) + return error; + } + + /* + * Increment the search key until we find at least one allocation + * candidate or if the extent we found was larger. Otherwise, double the + * search key to optimize the search. Efficiency is more important here + * than absolute best locality. + */ + cur_len <<= 1; + if (!acur->len || acur->cur_len >= cur_len) + acur->cur_len++; + else + acur->cur_len = cur_len; + + return error; +} + +/* * Deal with the case where only small freespaces remain. Either return the * contents of the last freespace record, or allocate space from the freelist if * there is nothing in the tree. @@ -1261,12 +1333,11 @@ xfs_alloc_walk_iter( } /* - * Search in the by-bno btree to the left and to the right simultaneously until - * in each case we find a large enough free extent or run into the edge of the - * tree. When we run into the edge of the tree, we deactivate that cursor. + * Search the by-bno and by-size btrees in parallel in search of an extent with + * ideal locality based on the NEAR mode ->agbno locality hint. */ STATIC int -xfs_alloc_ag_vextent_bnobt( +xfs_alloc_ag_vextent_locality( struct xfs_alloc_arg *args, struct xfs_alloc_cur *acur, int *stat) @@ -1281,6 +1352,9 @@ xfs_alloc_ag_vextent_bnobt( *stat = 0; + error = xfs_alloc_lookup_ge(acur->cnt, args->agbno, acur->cur_len, &i); + if (error) + return error; error = xfs_alloc_lookup_le(acur->bnolt, args->agbno, 0, &i); if (error) return error; @@ -1289,12 +1363,37 @@ xfs_alloc_ag_vextent_bnobt( return error; /* - * Loop going left with the leftward cursor, right with the rightward - * cursor, until either both directions give up or we find an entry at - * least as big as minlen. + * Search the bnobt and cntbt in parallel. Search the bnobt left and + * right and lookup the closest extent to the locality hint for each + * extent size key in the cntbt. The entire search terminates + * immediately on a bnobt hit because that means we've found best case + * locality. Otherwise the search continues until the cntbt cursor runs + * off the end of the tree. If no allocation candidate is found at this + * point, give up on locality, walk backwards from the end of the cntbt + * and take the first available extent. + * + * The parallel tree searches balance each other out to provide fairly + * consistent performance for various situations. The bnobt search can + * have pathological behavior in the worst case scenario of larger + * allocation requests and fragmented free space. On the other hand, the + * bnobt is able to satisfy most smaller allocation requests much more + * quickly than the cntbt. The cntbt search can sift through fragmented + * free space and sets of free extents for larger allocation requests + * more quickly than the bnobt. Since the locality hint is just a hint + * and we don't want to scan the entire bnobt for perfect locality, the + * cntbt search essentially bounds the bnobt search such that we can + * find good enough locality at reasonable performance in most cases. */ while (xfs_alloc_cur_active(acur->bnolt) || - xfs_alloc_cur_active(acur->bnogt)) { + xfs_alloc_cur_active(acur->bnogt) || + xfs_alloc_cur_active(acur->cnt)) { + + trace_xfs_alloc_cur_lookup(args); + + /* + * Search the bnobt left and right. In the case of a hit, finish + * the search in the opposite direction and we're done. + */ error = xfs_alloc_walk_iter(args, acur, acur->bnolt, false, true, 1, &i); if (error) @@ -1305,7 +1404,6 @@ xfs_alloc_ag_vextent_bnobt( fbinc = true; break; } - error = xfs_alloc_walk_iter(args, acur, acur->bnogt, true, true, 1, &i); if (error) @@ -1316,9 +1414,40 @@ xfs_alloc_ag_vextent_bnobt( fbinc = false; break; } + + /* + * Check the extent with best locality based on the current + * extent size search key and keep track of the best candidate. + */ + error = xfs_alloc_cntbt_iter(args, acur); + if (error) + return error; + if (!xfs_alloc_cur_active(acur->cnt)) { + trace_xfs_alloc_cur_lookup_done(args); + break; + } + } + + /* + * If we failed to find anything due to busy extents, return empty + * handed so the caller can flush and retry. If no busy extents were + * found, walk backwards from the end of the cntbt as a last resort. + */ + if (!xfs_alloc_cur_active(acur->cnt) && !acur->len && !acur->busy) { + error = xfs_btree_decrement(acur->cnt, 0, &i); + if (error) + return error; + if (i) { + acur->cnt->bc_private.a.priv.abt.active = true; + fbcur = acur->cnt; + fbinc = false; + } } - /* search the opposite direction for a better entry */ + /* + * Search in the opposite direction for a better entry in the case of + * a bnobt hit or walk backwards from the end of the cntbt. + */ if (fbcur) { error = xfs_alloc_walk_iter(args, acur, fbcur, fbinc, true, -1, &i); @@ -1447,9 +1576,10 @@ restart: } /* - * Second algorithm. Search the bnobt left and right. + * Second algorithm. Combined cntbt and bnobt search to find ideal + * locality. */ - error = xfs_alloc_ag_vextent_bnobt(args, &acur, &i); + error = xfs_alloc_ag_vextent_locality(args, &acur, &i); if (error) goto out; |