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xfs: get rid of unnecessary xfs_perag_{get,put} pairs

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In the course of some operations, we look up the perag from
the mount multiple times to get or change perag information.
These are often very short pieces of code, so while the
lookup cost is generally low, the cost of the lookup is far
higher than the cost of the operation we are doing on the
perag.

Since we changed buffers to hold references to the perag
they are cached in, many modification contexts already hold
active references to the perag that are held across these
operations. This is especially true for any operation that
is serialised by an allocation group header buffer.

In these cases, we can just use the buffer's reference to
the perag to avoid needing to do lookups to access the
perag. This means that many operations don't need to do
perag lookups at all to access the perag because they've
already looked up objects that own persistent references
and hence can use that reference instead.

Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Gao Xiang 2020-07-13 09:13:00 -07:00 • committed by Darrick J. Wong
parent c3f2375b90
commit 92a005448f
8 changed files with 34 additions and 91 deletions
Download patch file Download diff file Expand all files Collapse all files

22
fs/xfs/libxfs/xfs_alloc.c
View file

@ -710,13 +710,12 @@ xfs_alloc_read_agfl(
STATIC int
xfs_alloc_update_counters(
struct xfs_trans *tp,
struct xfs_perag *pag,
struct xfs_buf *agbp,
long len)
{
struct xfs_agf *agf = agbp->b_addr;
pag->pagf_freeblks += len;
agbp->b_pag->pagf_freeblks += len;
be32_add_cpu(&agf->agf_freeblks, len);
xfs_trans_agblocks_delta(tp, len);
@ -1175,8 +1174,7 @@ xfs_alloc_ag_vextent(
}
if (!args->wasfromfl) {
error = xfs_alloc_update_counters(args->tp, args->pag,
args->agbp,
error = xfs_alloc_update_counters(args->tp, args->agbp,
-((long)(args->len)));
if (error)
return error;
@ -1887,7 +1885,6 @@ xfs_free_ag_extent(
enum xfs_ag_resv_type type)
{
struct xfs_mount *mp;
struct xfs_perag *pag;
struct xfs_btree_cur *bno_cur;
struct xfs_btree_cur *cnt_cur;
xfs_agblock_t gtbno; /* start of right neighbor */
@ -2167,10 +2164,8 @@ xfs_free_ag_extent(
/*
* Update the freespace totals in the ag and superblock.
*/
pag = xfs_perag_get(mp, agno);
error = xfs_alloc_update_counters(tp, pag, agbp, len);
xfs_ag_resv_free_extent(pag, type, tp, len);
xfs_perag_put(pag);
error = xfs_alloc_update_counters(tp, agbp, len);
xfs_ag_resv_free_extent(agbp->b_pag, type, tp, len);
if (error)
goto error0;
@ -2689,7 +2684,7 @@ xfs_alloc_get_freelist(
if (be32_to_cpu(agf->agf_flfirst) == xfs_agfl_size(mp))
agf->agf_flfirst = 0;
pag = xfs_perag_get(mp, be32_to_cpu(agf->agf_seqno));
pag = agbp->b_pag;
ASSERT(!pag->pagf_agflreset);
be32_add_cpu(&agf->agf_flcount, -1);
xfs_trans_agflist_delta(tp, -1);
@ -2701,7 +2696,6 @@ xfs_alloc_get_freelist(
pag->pagf_btreeblks++;
logflags |= XFS_AGF_BTREEBLKS;
}
xfs_perag_put(pag);
xfs_alloc_log_agf(tp, agbp, logflags);
*bnop = bno;
@ -2797,7 +2791,7 @@ xfs_alloc_put_freelist(
if (be32_to_cpu(agf->agf_fllast) == xfs_agfl_size(mp))
agf->agf_fllast = 0;
pag = xfs_perag_get(mp, be32_to_cpu(agf->agf_seqno));
pag = agbp->b_pag;
ASSERT(!pag->pagf_agflreset);
be32_add_cpu(&agf->agf_flcount, 1);
xfs_trans_agflist_delta(tp, 1);
@ -2809,7 +2803,6 @@ xfs_alloc_put_freelist(
pag->pagf_btreeblks--;
logflags |= XFS_AGF_BTREEBLKS;
}
xfs_perag_put(pag);
xfs_alloc_log_agf(tp, agbp, logflags);
@ -3006,7 +2999,7 @@ xfs_alloc_read_agf(
ASSERT(!(*bpp)->b_error);
agf = (*bpp)->b_addr;
pag = xfs_perag_get(mp, agno);
pag = (*bpp)->b_pag;
if (!pag->pagf_init) {
pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
pag->pagf_btreeblks = be32_to_cpu(agf->agf_btreeblks);
@ -3034,7 +3027,6 @@ xfs_alloc_read_agf(
be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
}
#endif
xfs_perag_put(pag);
return 0;
}