@@ -39,7 +39,6 @@ struct workqueue_struct *xfs_alloc_wq;
#define XFSA_FIXUP_CNT_OK 2
STATIC int xfs_alloc_ag_vextent_exact(xfs_alloc_arg_t *);
-STATIC int xfs_alloc_ag_vextent_near(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_size(xfs_alloc_arg_t *);
/*
@@ -712,8 +711,435 @@ xfs_alloc_update_counters(
}
/*
- * Allocation group level functions.
+ * Block allocation algorithm and data structures.
*/
+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 */
+ xfs_extlen_t len; /* alloc len */
+ xfs_extlen_t diff; /* diff from search bno */
+ unsigned busy_gen;/* busy state */
+ bool busy;
+};
+
+/*
+ * Set up cursors, etc. in the extent allocation cursor. This function can be
+ * called multiple times to reset an initialized structure without having to
+ * reallocate cursors.
+ */
+static int
+xfs_alloc_cur_setup(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur)
+{
+ xfs_agblock_t agbno = 0;
+ int error;
+ int i;
+
+ acur->cur_len = args->maxlen;
+ acur->rec_bno = 0;
+ acur->rec_len = 0;
+ acur->bno = 0;
+ acur->len = 0;
+ acur->diff = -1;
+ acur->busy = false;
+ acur->busy_gen = 0;
+
+ if (args->agbno != NULLAGBLOCK)
+ agbno = args->agbno;
+
+ /*
+ * Initialize the cntbt cursor and determine whether to start the search
+ * at maxlen or minlen. THIS_AG allocation mode expects the cursor at
+ * the first available maxlen extent or at the end of the tree.
+ */
+ if (!acur->cnt)
+ acur->cnt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_CNT);
+ error = xfs_alloc_lookup_ge(acur->cnt, agbno, acur->cur_len, &i);
+ if (!i) {
+ acur->cur_len = args->minlen;
+ error = xfs_alloc_lookup_ge(acur->cnt, agbno, acur->cur_len,
+ &i);
+ if (error)
+ return error;
+ }
+
+ /* init bnobt left/right search cursors */
+ if (!acur->bnolt)
+ acur->bnolt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_BNO);
+ error = xfs_alloc_lookup_le(acur->bnolt, agbno, args->maxlen, &i);
+ if (error)
+ return error;
+
+ if (!acur->bnogt)
+ acur->bnogt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_BNO);
+ error = xfs_alloc_lookup_ge(acur->bnogt, agbno, args->maxlen, &i);
+
+ return error;
+}
+
+static void
+xfs_alloc_cur_close(
+ struct xfs_alloc_cur *acur,
+ bool error)
+{
+ int cur_error = XFS_BTREE_NOERROR;
+
+ if (error)
+ cur_error = XFS_BTREE_ERROR;
+
+ if (acur->cnt)
+ xfs_btree_del_cursor(acur->cnt, cur_error);
+ if (acur->bnolt)
+ xfs_btree_del_cursor(acur->bnolt, cur_error);
+ if (acur->bnogt)
+ xfs_btree_del_cursor(acur->bnogt, cur_error);
+ acur->cnt = acur->bnolt = acur->bnogt = NULL;
+}
+
+/*
+ * Check an extent for allocation and track the best available candidate in the
+ * allocation structure. The cursor is deactivated if it has entered an out of
+ * range state based on allocation arguments. Optionally return the extent
+ * extent geometry and allocation status if requested by the caller.
+ */
+static int
+xfs_alloc_cur_check(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur,
+ xfs_agblock_t *obno,
+ xfs_extlen_t *olen,
+ bool *new)
+{
+ int error, i;
+ xfs_agblock_t bno, bnoa, bnew;
+ xfs_extlen_t len, lena, diff = -1;
+ bool busy;
+ unsigned busy_gen = 0;
+ bool deactivate = false;
+ bool isbnobt = cur->bc_btnum == XFS_BTNUM_BNO;
+
+ if (new)
+ *new = false;
+
+ error = xfs_alloc_get_rec(cur, &bno, &len, &i);
+ if (error)
+ return error;
+ XFS_WANT_CORRUPTED_RETURN(args->mp, i == 1);
+ if (obno)
+ *obno = bno;
+ if (olen)
+ *olen = len;
+
+ /*
+ * Check against minlen and then compute and check the aligned record.
+ * If a cntbt record is out of size range (i.e., we're walking
+ * backwards) or a bnobt record is out of locality range, deactivate the
+ * cursor.
+ */
+ if (len < args->minlen) {
+ deactivate = !isbnobt;
+ goto fail;
+ }
+
+ busy = xfs_alloc_compute_aligned(args, bno, len, &bnoa, &lena,
+ &busy_gen);
+ acur->busy |= busy;
+ if (busy)
+ acur->busy_gen = busy_gen;
+ if (bnoa < args->min_agbno || bnoa > args->max_agbno) {
+ deactivate = isbnobt;
+ goto fail;
+ }
+ if (lena < args->minlen)
+ goto fail;
+
+ args->len = XFS_EXTLEN_MIN(lena, args->maxlen);
+ xfs_alloc_fix_len(args);
+ ASSERT(args->len >= args->minlen);
+ if (args->len < acur->len)
+ goto fail;
+
+ /*
+ * We have an aligned record that satisfies minlen and beats the current
+ * candidate length. The remaining locality checks are specific to near
+ * allocation mode.
+ */
+ ASSERT(args->type == XFS_ALLOCTYPE_NEAR_BNO);
+ diff = xfs_alloc_compute_diff(args->agbno, args->len,
+ args->alignment, args->datatype,
+ bnoa, lena, &bnew);
+ if (bnew == NULLAGBLOCK)
+ goto fail;
+ if (diff > acur->diff) {
+ /* deactivate bnobt cursor with worse locality */
+ deactivate = isbnobt;
+ goto fail;
+ }
+ if (args->len < acur->len)
+ goto fail;
+
+ /* found a new candidate extent */
+ acur->rec_bno = bno;
+ acur->rec_len = len;
+ acur->bno = bnew;
+ acur->len = args->len;
+ acur->diff = diff;
+ if (new)
+ *new = true;
+ trace_xfs_alloc_cur_new(args->mp, acur->bno, acur->len, acur->diff);
+ return 0;
+
+fail:
+ if (deactivate)
+ cur->bc_private.a.priv.abt.active = false;
+ return 0;
+}
+
+/*
+ * Complete an allocation of a candidate extent. Remove the extent from both
+ * trees and update the args structure.
+ */
+STATIC int
+xfs_alloc_cur_finish(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur)
+{
+ int error;
+
+ ASSERT(acur->len);
+ ASSERT(acur->cnt && acur->bnolt);
+
+ error = xfs_alloc_fixup_trees(acur->cnt, acur->bnolt, acur->rec_bno,
+ acur->rec_len, acur->bno, acur->len, 0);
+ if (error)
+ return error;
+
+ args->agbno = acur->bno;
+ args->len = acur->len;
+ args->wasfromfl = 0;
+
+ trace_xfs_alloc_cur(args);
+ return 0;
+}
+
+/*
+ * 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_lookup_iter(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur)
+{
+ 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;
+
+ /* check the current record and update search length from it */
+ error = xfs_alloc_cur_check(args, acur, cur, &bno, &len, NULL);
+ 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,
+ NULL, NULL, NULL);
+ }
+ }
+ 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;
+}
+
+/*
+ * Incremental lookup algorithm. Walk a btree in either direction looking for
+ * candidate extents. This works for either bnobt (locality allocation) or cntbt
+ * (by-size allocation) cursors.
+ */
+STATIC int
+xfs_alloc_walk_iter(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur,
+ bool increment,
+ bool findone,
+ int iters,
+ int *stat)
+{
+ int error;
+ int i;
+ bool found = false;
+
+ if (!xfs_alloc_cur_active(cur))
+ return 0;
+
+ *stat = 0;
+ for (; iters > 0; iters--) {
+ error = xfs_alloc_cur_check(args, acur, cur, NULL, NULL,
+ &found);
+ if (error)
+ return error;
+ if (found) {
+ *stat = 1;
+ if (findone)
+ break;
+ }
+ if (!xfs_alloc_cur_active(cur))
+ break;
+
+ if (increment)
+ error = xfs_btree_increment(cur, 0, &i);
+ else
+ error = xfs_btree_decrement(cur, 0, &i);
+ if (error)
+ return error;
+ if (i == 0) {
+ cur->bc_private.a.priv.abt.active = false;
+ break;
+ }
+ }
+
+ return error;
+}
+
+/*
+ * High level locality allocation algorithm. Search the bnobt (left and right)
+ * in parallel with locality-optimized cntbt lookups to find an extent with
+ * ideal locality.
+ */
+STATIC int
+xfs_alloc_ag_vextent_cur(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ int *stat)
+{
+ int error;
+ int i;
+ unsigned int findbestcount;
+ struct xfs_btree_cur *fbcur = NULL;
+ bool fbinc = false;
+
+ ASSERT(acur->cnt);
+ ASSERT(args->type != XFS_ALLOCTYPE_THIS_AG);
+ findbestcount = args->mp->m_alloc_mxr[0];
+ *stat = 0;
+
+ /* search as long as we have at least one active cursor */
+ while (xfs_alloc_cur_active(acur->cnt) ||
+ xfs_alloc_cur_active(acur->bnolt) ||
+ xfs_alloc_cur_active(acur->bnogt)) {
+ /*
+ * Search the bnobt left and right. If either of these find a
+ * suitable extent, we know we've found ideal locality. Do a
+ * capped search in the opposite direction and we're done.
+ */
+ error = xfs_alloc_walk_iter(args, acur, acur->bnolt, false,
+ true, 1, &i);
+ if (error)
+ return error;
+ if (i) {
+ fbcur = acur->bnogt;
+ fbinc = true;
+ break;
+ }
+
+ error = xfs_alloc_walk_iter(args, acur, acur->bnogt, true,
+ true, 1, &i);
+ if (error)
+ return error;
+ if (i) {
+ fbcur = acur->bnolt;
+ break;
+ }
+
+ /*
+ * Search the cntbt for a maximum sized extent with ideal
+ * locality. The lookup search terminates on reaching the end of
+ * the cntbt. Break out of the loop if this occurs to throttle
+ * the bnobt scans.
+ */
+ error = xfs_alloc_lookup_iter(args, acur, acur->cnt);
+ if (error)
+ return error;
+ if (!xfs_alloc_cur_active(acur->cnt)) {
+ if (!acur->len) {
+ fbcur = acur->cnt;
+ error = xfs_btree_decrement(fbcur, 0, &i);
+ if (error)
+ return error;
+ if (i)
+ fbcur->bc_private.a.priv.abt.active = true;
+ }
+ break;
+ }
+ }
+
+ /*
+ * Perform a best-effort search in the opposite direction from a bnobt
+ * allocation or backwards from the end of the cntbt if we couldn't find
+ * a maxlen extent.
+ */
+ if (fbcur) {
+ error = xfs_alloc_walk_iter(args, acur, fbcur, fbinc, true,
+ findbestcount, &i);
+ if (error)
+ return error;
+ }
+
+ if (acur->len)
+ *stat = 1;
+
+ return error;
+}
/*
* Deal with the case where only small freespaces remain. Either return the
@@ -817,6 +1243,81 @@ xfs_alloc_ag_vextent_small(
return error;
}
+/*
+ * Allocate a variable extent near bno in the allocation group agno.
+ * Extent's length (returned in len) will be between minlen and maxlen,
+ * and of the form k * prod + mod unless there's nothing that large.
+ * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
+ */
+STATIC int /* error */
+xfs_alloc_ag_vextent_type(
+ xfs_alloc_arg_t *args) /* allocation argument structure */
+{
+ struct xfs_alloc_cur acur = {0,};
+ int error; /* error code */
+ int i; /* result code, temporary */
+ xfs_agblock_t bno; /* start bno of left side entry */
+ xfs_extlen_t len; /* length of left side entry */
+
+ /* handle unitialized agbno range so caller doesn't have to */
+ if (!args->min_agbno && !args->max_agbno)
+ args->max_agbno = args->mp->m_sb.sb_agblocks - 1;
+ ASSERT(args->min_agbno <= args->max_agbno);
+
+ /* clamp agbno to the range if it's outside */
+ if (args->agbno < args->min_agbno)
+ args->agbno = args->min_agbno;
+ if (args->agbno > args->max_agbno)
+ args->agbno = args->max_agbno;
+
+restart:
+ /* set up cursors and allocation tracking structure based on args */
+ error = xfs_alloc_cur_setup(args, &acur);
+ if (error)
+ goto out;
+
+ error = xfs_alloc_ag_vextent_cur(args, &acur, &i);
+ if (error)
+ goto out;
+
+ /*
+ * If we got an extent, finish the allocation. Otherwise check for busy
+ * extents and retry or attempt a small allocation.
+ */
+ if (i) {
+ error = xfs_alloc_cur_finish(args, &acur);
+ if (error)
+ goto out;
+ } else {
+ if (acur.busy) {
+ trace_xfs_alloc_ag_busy(args);
+ xfs_extent_busy_flush(args->mp, args->pag,
+ acur.busy_gen);
+ goto restart;
+ }
+
+ /*
+ * We get here if we can't satisfy minlen or the trees are
+ * empty. We don't pass a cursor so this returns an AGFL block
+ * (i == 0) or nothing.
+ */
+ error = xfs_alloc_ag_vextent_small(args, NULL, &bno, &len, &i);
+ if (error)
+ goto out;
+ ASSERT(i == 0 || (i && len == 0));
+ trace_xfs_alloc_ag_noentry(args);
+
+ args->agbno = bno;
+ args->len = len;
+ }
+
+out:
+ xfs_alloc_cur_close(&acur, error);
+ if (error)
+ trace_xfs_alloc_ag_error(args);
+ return error;
+}
+
/*
* Allocate a variable extent in the allocation group agno.
* Type and bno are used to determine where in the allocation group the
@@ -846,7 +1347,7 @@ xfs_alloc_ag_vextent(
error = xfs_alloc_ag_vextent_size(args);
break;
case XFS_ALLOCTYPE_NEAR_BNO:
- error = xfs_alloc_ag_vextent_near(args);
+ error = xfs_alloc_ag_vextent_type(args);
break;
case XFS_ALLOCTYPE_THIS_BNO:
error = xfs_alloc_ag_vextent_exact(args);
@@ -1004,503 +1505,6 @@ xfs_alloc_ag_vextent_exact(
return error;
}
-/*
- * Search the btree in a given direction via the search cursor and compare
- * the records found against the good extent we've already found.
- */
-STATIC int
-xfs_alloc_find_best_extent(
- struct xfs_alloc_arg *args, /* allocation argument structure */
- struct xfs_btree_cur **gcur, /* good cursor */
- struct xfs_btree_cur **scur, /* searching cursor */
- xfs_agblock_t gdiff, /* difference for search comparison */
- xfs_agblock_t *sbno, /* extent found by search */
- xfs_extlen_t *slen, /* extent length */
- xfs_agblock_t *sbnoa, /* aligned extent found by search */
- xfs_extlen_t *slena, /* aligned extent length */
- int dir) /* 0 = search right, 1 = search left */
-{
- xfs_agblock_t new;
- xfs_agblock_t sdiff;
- int error;
- int i;
- unsigned busy_gen;
-
- /* The good extent is perfect, no need to search. */
- if (!gdiff)
- goto out_use_good;
-
- /*
- * Look until we find a better one, run out of space or run off the end.
- */
- do {
- error = xfs_alloc_get_rec(*scur, sbno, slen, &i);
- if (error)
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- xfs_alloc_compute_aligned(args, *sbno, *slen,
- sbnoa, slena, &busy_gen);
-
- /*
- * The good extent is closer than this one.
- */
- if (!dir) {
- if (*sbnoa > args->max_agbno)
- goto out_use_good;
- if (*sbnoa >= args->agbno + gdiff)
- goto out_use_good;
- } else {
- if (*sbnoa < args->min_agbno)
- goto out_use_good;
- if (*sbnoa <= args->agbno - gdiff)
- goto out_use_good;
- }
-
- /*
- * Same distance, compare length and pick the best.
- */
- if (*slena >= args->minlen) {
- args->len = XFS_EXTLEN_MIN(*slena, args->maxlen);
- xfs_alloc_fix_len(args);
-
- sdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment,
- args->datatype, *sbnoa,
- *slena, &new);
-
- /*
- * Choose closer size and invalidate other cursor.
- */
- if (sdiff < gdiff)
- goto out_use_search;
- goto out_use_good;
- }
-
- if (!dir)
- error = xfs_btree_increment(*scur, 0, &i);
- else
- error = xfs_btree_decrement(*scur, 0, &i);
- if (error)
- goto error0;
- } while (i);
-
-out_use_good:
- xfs_btree_del_cursor(*scur, XFS_BTREE_NOERROR);
- *scur = NULL;
- return 0;
-
-out_use_search:
- xfs_btree_del_cursor(*gcur, XFS_BTREE_NOERROR);
- *gcur = NULL;
- return 0;
-
-error0:
- /* caller invalidates cursors */
- return error;
-}
-
-/*
- * Allocate a variable extent near bno in the allocation group agno.
- * Extent's length (returned in len) will be between minlen and maxlen,
- * and of the form k * prod + mod unless there's nothing that large.
- * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
- */
-STATIC int /* error */
-xfs_alloc_ag_vextent_near(
- xfs_alloc_arg_t *args) /* allocation argument structure */
-{
- xfs_btree_cur_t *bno_cur_gt; /* cursor for bno btree, right side */
- xfs_btree_cur_t *bno_cur_lt; /* cursor for bno btree, left side */
- xfs_btree_cur_t *cnt_cur; /* cursor for count btree */
- xfs_agblock_t gtbno; /* start bno of right side entry */
- xfs_agblock_t gtbnoa; /* aligned ... */
- xfs_extlen_t gtdiff; /* difference to right side entry */
- xfs_extlen_t gtlen; /* length of right side entry */
- xfs_extlen_t gtlena; /* aligned ... */
- xfs_agblock_t gtnew; /* useful start bno of right side */
- int error; /* error code */
- int i; /* result code, temporary */
- int j; /* result code, temporary */
- xfs_agblock_t ltbno; /* start bno of left side entry */
- xfs_agblock_t ltbnoa; /* aligned ... */
- xfs_extlen_t ltdiff; /* difference to left side entry */
- xfs_extlen_t ltlen; /* length of left side entry */
- xfs_extlen_t ltlena; /* aligned ... */
- xfs_agblock_t ltnew; /* useful start bno of left side */
- xfs_extlen_t rlen; /* length of returned extent */
- bool busy;
- unsigned busy_gen;
-#ifdef DEBUG
- /*
- * Randomly don't execute the first algorithm.
- */
- int dofirst; /* set to do first algorithm */
-
- dofirst = prandom_u32() & 1;
-#endif
-
- /* handle unitialized agbno range so caller doesn't have to */
- if (!args->min_agbno && !args->max_agbno)
- args->max_agbno = args->mp->m_sb.sb_agblocks - 1;
- ASSERT(args->min_agbno <= args->max_agbno);
-
- /* clamp agbno to the range if it's outside */
- if (args->agbno < args->min_agbno)
- args->agbno = args->min_agbno;
- if (args->agbno > args->max_agbno)
- args->agbno = args->max_agbno;
-
-restart:
- bno_cur_lt = NULL;
- bno_cur_gt = NULL;
- ltlen = 0;
- gtlena = 0;
- ltlena = 0;
- busy = false;
-
- /*
- * Get a cursor for the by-size btree.
- */
- cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
- args->agno, XFS_BTNUM_CNT);
-
- /*
- * See if there are any free extents as big as maxlen.
- */
- if ((error = xfs_alloc_lookup_ge(cnt_cur, 0, args->maxlen, &i)))
- goto error0;
- /*
- * If none, then pick up the last entry in the tree unless the
- * tree is empty.
- */
- if (!i) {
- if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, <bno,
- <len, &i)))
- goto error0;
- if (i == 0 || ltlen == 0) {
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- trace_xfs_alloc_near_noentry(args);
- return 0;
- }
- ASSERT(i == 1);
- }
- args->wasfromfl = 0;
-
- /*
- * First algorithm.
- * If the requested extent is large wrt the freespaces available
- * in this a.g., then the cursor will be pointing to a btree entry
- * near the right edge of the tree. If it's in the last btree leaf
- * block, then we just examine all the entries in that block
- * that are big enough, and pick the best one.
- * This is written as a while loop so we can break out of it,
- * but we never loop back to the top.
- */
- while (xfs_btree_islastblock(cnt_cur, 0)) {
- xfs_extlen_t bdiff;
- int besti=0;
- xfs_extlen_t blen=0;
- xfs_agblock_t bnew=0;
-
-#ifdef DEBUG
- if (dofirst)
- break;
-#endif
- /*
- * Start from the entry that lookup found, sequence through
- * all larger free blocks. If we're actually pointing at a
- * record smaller than maxlen, go to the start of this block,
- * and skip all those smaller than minlen.
- */
- if (ltlen || args->alignment > 1) {
- cnt_cur->bc_ptrs[0] = 1;
- do {
- if ((error = xfs_alloc_get_rec(cnt_cur, <bno,
- <len, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- if (ltlen >= args->minlen)
- break;
- if ((error = xfs_btree_increment(cnt_cur, 0, &i)))
- goto error0;
- } while (i);
- ASSERT(ltlen >= args->minlen);
- if (!i)
- break;
- }
- i = cnt_cur->bc_ptrs[0];
- for (j = 1, blen = 0, bdiff = 0;
- !error && j && (blen < args->maxlen || bdiff > 0);
- error = xfs_btree_increment(cnt_cur, 0, &j)) {
- /*
- * For each entry, decide if it's better than
- * the previous best entry.
- */
- if ((error = xfs_alloc_get_rec(cnt_cur, <bno, <len, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy = xfs_alloc_compute_aligned(args, ltbno, ltlen,
- <bnoa, <lena, &busy_gen);
- if (ltlena < args->minlen)
- continue;
- if (ltbnoa < args->min_agbno || ltbnoa > args->max_agbno)
- continue;
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- ASSERT(args->len >= args->minlen);
- if (args->len < blen)
- continue;
- ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, ltbnoa,
- ltlena, <new);
- if (ltnew != NULLAGBLOCK &&
- (args->len > blen || ltdiff < bdiff)) {
- bdiff = ltdiff;
- bnew = ltnew;
- blen = args->len;
- besti = cnt_cur->bc_ptrs[0];
- }
- }
- /*
- * It didn't work. We COULD be in a case where
- * there's a good record somewhere, so try again.
- */
- if (blen == 0)
- break;
- /*
- * Point at the best entry, and retrieve it again.
- */
- cnt_cur->bc_ptrs[0] = besti;
- if ((error = xfs_alloc_get_rec(cnt_cur, <bno, <len, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- ASSERT(ltbno + ltlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
- args->len = blen;
-
- /*
- * We are allocating starting at bnew for blen blocks.
- */
- args->agbno = bnew;
- ASSERT(bnew >= ltbno);
- ASSERT(bnew + blen <= ltbno + ltlen);
- /*
- * Set up a cursor for the by-bno tree.
- */
- bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp,
- args->agbp, args->agno, XFS_BTNUM_BNO);
- /*
- * Fix up the btree entries.
- */
- if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno,
- ltlen, bnew, blen, XFSA_FIXUP_CNT_OK)))
- goto error0;
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
-
- trace_xfs_alloc_near_first(args);
- return 0;
- }
- /*
- * Second algorithm.
- * Search in the by-bno tree to the left and to the right
- * simultaneously, until in each case we find a space big enough,
- * or run into the edge of the tree. When we run into the edge,
- * we deallocate that cursor.
- * If both searches succeed, we compare the two spaces and pick
- * the better one.
- * With alignment, it's possible for both to fail; the upper
- * level algorithm that picks allocation groups for allocations
- * is not supposed to do this.
- */
- /*
- * Allocate and initialize the cursor for the leftward search.
- */
- bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
- args->agno, XFS_BTNUM_BNO);
- /*
- * Lookup <= bno to find the leftward search's starting point.
- */
- if ((error = xfs_alloc_lookup_le(bno_cur_lt, args->agbno, args->maxlen, &i)))
- goto error0;
- if (!i) {
- /*
- * Didn't find anything; use this cursor for the rightward
- * search.
- */
- bno_cur_gt = bno_cur_lt;
- bno_cur_lt = NULL;
- }
- /*
- * Found something. Duplicate the cursor for the rightward search.
- */
- else if ((error = xfs_btree_dup_cursor(bno_cur_lt, &bno_cur_gt)))
- goto error0;
- /*
- * Increment the cursor, so we will point at the entry just right
- * of the leftward entry if any, or to the leftmost entry.
- */
- if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
- goto error0;
- if (!i) {
- /*
- * It failed, there are no rightward entries.
- */
- xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_NOERROR);
- bno_cur_gt = NULL;
- }
- /*
- * 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.
- */
- do {
- if (bno_cur_lt) {
- if ((error = xfs_alloc_get_rec(bno_cur_lt, <bno, <len, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy |= xfs_alloc_compute_aligned(args, ltbno, ltlen,
- <bnoa, <lena, &busy_gen);
- if (ltlena >= args->minlen && ltbnoa >= args->min_agbno)
- break;
- if ((error = xfs_btree_decrement(bno_cur_lt, 0, &i)))
- goto error0;
- if (!i || ltbnoa < args->min_agbno) {
- xfs_btree_del_cursor(bno_cur_lt,
- XFS_BTREE_NOERROR);
- bno_cur_lt = NULL;
- }
- }
- if (bno_cur_gt) {
- if ((error = xfs_alloc_get_rec(bno_cur_gt, >bno, >len, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy |= xfs_alloc_compute_aligned(args, gtbno, gtlen,
- >bnoa, >lena, &busy_gen);
- if (gtlena >= args->minlen && gtbnoa <= args->max_agbno)
- break;
- if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
- goto error0;
- if (!i || gtbnoa > args->max_agbno) {
- xfs_btree_del_cursor(bno_cur_gt,
- XFS_BTREE_NOERROR);
- bno_cur_gt = NULL;
- }
- }
- } while (bno_cur_lt || bno_cur_gt);
-
- /*
- * Got both cursors still active, need to find better entry.
- */
- if (bno_cur_lt && bno_cur_gt) {
- if (ltlena >= args->minlen) {
- /*
- * Left side is good, look for a right side entry.
- */
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, ltbnoa,
- ltlena, <new);
-
- error = xfs_alloc_find_best_extent(args,
- &bno_cur_lt, &bno_cur_gt,
- ltdiff, >bno, >len,
- >bnoa, >lena,
- 0 /* search right */);
- } else {
- ASSERT(gtlena >= args->minlen);
-
- /*
- * Right side is good, look for a left side entry.
- */
- args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
- xfs_alloc_fix_len(args);
- gtdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, gtbnoa,
- gtlena, >new);
-
- error = xfs_alloc_find_best_extent(args,
- &bno_cur_gt, &bno_cur_lt,
- gtdiff, <bno, <len,
- <bnoa, <lena,
- 1 /* search left */);
- }
-
- if (error)
- goto error0;
- }
-
- /*
- * If we couldn't get anything, give up.
- */
- if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
-
- if (busy) {
- trace_xfs_alloc_near_busy(args);
- xfs_extent_busy_flush(args->mp, args->pag, busy_gen);
- goto restart;
- }
- trace_xfs_alloc_size_neither(args);
- args->agbno = NULLAGBLOCK;
- return 0;
- }
-
- /*
- * At this point we have selected a freespace entry, either to the
- * left or to the right. If it's on the right, copy all the
- * useful variables to the "left" set so we only have one
- * copy of this code.
- */
- if (bno_cur_gt) {
- bno_cur_lt = bno_cur_gt;
- bno_cur_gt = NULL;
- ltbno = gtbno;
- ltbnoa = gtbnoa;
- ltlen = gtlen;
- ltlena = gtlena;
- j = 1;
- } else
- j = 0;
-
- /*
- * Fix up the length and compute the useful address.
- */
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- rlen = args->len;
- (void)xfs_alloc_compute_diff(args->agbno, rlen, args->alignment,
- args->datatype, ltbnoa, ltlena, <new);
- ASSERT(ltnew >= ltbno);
- ASSERT(ltnew + rlen <= ltbnoa + ltlena);
- ASSERT(ltnew + rlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
- ASSERT(ltnew >= args->min_agbno && ltnew <= args->max_agbno);
- args->agbno = ltnew;
-
- if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno, ltlen,
- ltnew, rlen, XFSA_FIXUP_BNO_OK)))
- goto error0;
-
- if (j)
- trace_xfs_alloc_near_greater(args);
- else
- trace_xfs_alloc_near_lesser(args);
-
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
- return 0;
-
- error0:
- trace_xfs_alloc_near_error(args);
- if (cnt_cur != NULL)
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
- if (bno_cur_lt != NULL)
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_ERROR);
- if (bno_cur_gt != NULL)
- xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_ERROR);
- return error;
-}
-
/*
* Allocate a variable extent anywhere in the allocation group agno.
* Extent's length (returned in len) will be between minlen and maxlen,
@@ -1635,14 +1635,10 @@ DEFINE_EVENT(xfs_alloc_class, name, \
DEFINE_ALLOC_EVENT(xfs_alloc_exact_done);
DEFINE_ALLOC_EVENT(xfs_alloc_exact_notfound);
DEFINE_ALLOC_EVENT(xfs_alloc_exact_error);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_nominleft);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_first);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_greater);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_lesser);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_error);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_noentry);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_busy);
-DEFINE_ALLOC_EVENT(xfs_alloc_size_neither);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_error);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_noentry);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_busy);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur);
DEFINE_ALLOC_EVENT(xfs_alloc_size_noentry);
DEFINE_ALLOC_EVENT(xfs_alloc_size_nominleft);
DEFINE_ALLOC_EVENT(xfs_alloc_size_done);
@@ -1658,6 +1654,27 @@ DEFINE_ALLOC_EVENT(xfs_alloc_vextent_noagbp);
DEFINE_ALLOC_EVENT(xfs_alloc_vextent_loopfailed);
DEFINE_ALLOC_EVENT(xfs_alloc_vextent_allfailed);
+TRACE_EVENT(xfs_alloc_cur_new,
+ TP_PROTO(struct xfs_mount *mp, xfs_agblock_t bno, xfs_extlen_t len,
+ xfs_extlen_t diff),
+ TP_ARGS(mp, bno, len, diff),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(xfs_agblock_t, bno)
+ __field(xfs_extlen_t, len)
+ __field(xfs_extlen_t, diff)
+ ),
+ TP_fast_assign(
+ __entry->dev = mp->m_super->s_dev;
+ __entry->bno = bno;
+ __entry->len = len;
+ __entry->diff = diff;
+ ),
+ TP_printk("dev %d:%d bno 0x%x len 0x%x diff 0x%x",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->bno, __entry->len, __entry->diff)
+)
+
DECLARE_EVENT_CLASS(xfs_da_class,
TP_PROTO(struct xfs_da_args *args),
TP_ARGS(args),
The extent allocation code in XFS has several allocation modes with unique implementations. This is slightly unfortunate as the allocation modes are not all that different from a high level perspective. The most involved mode is the near allocation mode which attempts to allocate an optimally sized extent with ideal locality with respect to a provided agbno. In the common case, a near mode allocation consists of a conditional scan of the last cntbt block followed by a concurrent left and right spanning search of the bnobt starting from the ideal point of locality in the bnobt. This works reasonably well as filesystems age via most common allocation patterns. If free space fragments as the filesystem ages, however, the near algorithm has very poor breakdown characteristics. If the extent size lookup happens to land outside (i.e., before) the last cntbt block, the alloc bypasses the cntbt entirely. If a suitably sized extent lies beyond a large enough number of unusable extents from the starting point(s) of the bnobt search, the bnobt search can take a significant amount of time to locate the target extent. This leads to pathological allocation latencies in certain workloads. The near allocation algorithm can be fundamentally improved to take advantage of a preexisting mechanism: that by-size cntbt record lookups can incorporate locality. This means that a single cntbt lookup can return the extent of a particular size with best locality. A single locality lookup only covers extents of the requested size, but for larger extent allocations, repeated locality lookups of increasing sizes can search more efficiently than the bnobt scan because it isolates the search space to extents of suitable size. Such a cntbt search may not always find the extent with absolute best locality, but the tradeoff for good enough locality for a more efficient scan is worthwhile because more often than not, extent size and contiguity are more important for performance than perfect locality for data allocations. This patch introduces generic allocation infrastructure for cursor setup/teardown, selected extent allocation and various means of btree scanning. Based on this infrastructure, it reimplements the near allocation algorithm to balance between repeated cntbt lookups and bnobt left/right scans as opposed to effectively choosing one search algorithm or the other. This provides more predictable allocation latency under breakdown conditions with good enough locality in the common case. The algorithm naturally balances between smaller and larger allocations as smaller allocations are more likely to be satisfied immediately from the bnobt whereas larger allocations are more likely satisfied by the cntbt. The generic infrastructure introduced by this patch will be reused to reduce code duplication between different, but conceptually similar allocation modes in subsequent patches. Signed-off-by: Brian Foster <bfoster@redhat.com> --- fs/xfs/libxfs/xfs_alloc.c | 1004 +++++++++++++++++++------------------ fs/xfs/xfs_trace.h | 33 +- 2 files changed, 529 insertions(+), 508 deletions(-)