[PATCH 0/3] xfs: miscellaneous improvements for 4.10

[PATCH 0/3] xfs: miscellaneous improvements for 4.10

[Dave Chinner]

Hi folks,

Some things that need review, hoepfully in time for the 4.10 cycle.
I've been running all these in my test kernels for some time now,
and they all seem stable and perform as expected. The btree stats
patch substantially reduces the icache footprint of the core btree
code. The rhashtable patch (many thanks to Lucas for writing the
original patch!) gets rid of most of the _xfs_buf_find() lookup
overhead. The CRC update optimisation patch (thanks to the
diagnosis, analysis and prototyping work done by Nick Piggin)
removes CRCs almost entirely from my kernel profiles on metadata
intensive workloads.

Comments, flames and thoughts welcome.

-Dave.

[PATCH 1/3] xfs: make xfs btree stats less huge

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

Embedding a switch statement in every btree stats inc/add adds a lot
of code overhead to the core btree infrastructure paths. Stats are
supposed to be small and lightweight, but the btree stats have
become big and bloated as we've added more btrees. It needs fixing
because the reflink code will just add more overhead again.

Convert the v2 btree stats to arrays instead of independent
variables, and instead use the type to index the specific btree
array via an enum. This allows us to use array based indexing
to update the stats, rather than having to derefence variables
specific to the btree type.

If we then wrap the xfsstats structure in a union and place uint32_t
array beside it, and calculate the correct btree stats array base
array index when creating a btree cursor,  we can easily access
entries in the stats structure without having to switch names based
on the btree type.

We then replace with the switch statement with a simple set of stats
wrapper macros, resulting in a significant simplification of the
btree stats code, and:

   text	   data	    bss	    dec	    hex	filename
  48905	    144	      8	  49057	   bfa1	fs/xfs/libxfs/xfs_btree.o.old
  36793	    144	      8	  36945	   9051	fs/xfs/libxfs/xfs_btree.o

it reduces the core btree infrastructure code size by close to 25%!

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/libxfs/xfs_alloc_btree.c    |   4 +
 fs/xfs/libxfs/xfs_bmap_btree.c     |   1 +
 fs/xfs/libxfs/xfs_btree.h          |  43 +--------
 fs/xfs/libxfs/xfs_ialloc_btree.c   |   2 +
 fs/xfs/libxfs/xfs_refcount_btree.c |   1 +
 fs/xfs/libxfs/xfs_rmap_btree.c     |   1 +
 fs/xfs/xfs_stats.c                 |  10 +-
 fs/xfs/xfs_stats.h                 | 192 ++++++++++++++-----------------------
 8 files changed, 91 insertions(+), 163 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index 5ba2dac5e67c..44cfcd03c451 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -428,6 +428,10 @@ xfs_allocbt_init_cursor(
 	cur->bc_btnum = btnum;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
 	cur->bc_ops = &xfs_allocbt_ops;
+	if (btnum == XFS_BTNUM_BNO)
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtb_2);
+	else
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_abtc_2);
 
 	if (btnum == XFS_BTNUM_CNT) {
 		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
index 8007d2ba9aef..94ad31d372ab 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -803,6 +803,7 @@ xfs_bmbt_init_cursor(
 	cur->bc_nlevels = be16_to_cpu(ifp->if_broot->bb_level) + 1;
 	cur->bc_btnum = XFS_BTNUM_BMAP;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
+	cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_bmbt_2);
 
 	cur->bc_ops = &xfs_bmbt_ops;
 	cur->bc_flags = XFS_BTREE_LONG_PTRS | XFS_BTREE_ROOT_IN_INODE;
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index c2b01d1c79ee..b69b947c4c1b 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -96,46 +96,10 @@ union xfs_btree_rec {
 /*
  * Generic stats interface
  */
-#define __XFS_BTREE_STATS_INC(mp, type, stat) \
-	XFS_STATS_INC(mp, xs_ ## type ## _2_ ## stat)
 #define XFS_BTREE_STATS_INC(cur, stat)	\
-do {    \
-	struct xfs_mount *__mp = cur->bc_mp; \
-	switch (cur->bc_btnum) {  \
-	case XFS_BTNUM_BNO: __XFS_BTREE_STATS_INC(__mp, abtb, stat); break; \
-	case XFS_BTNUM_CNT: __XFS_BTREE_STATS_INC(__mp, abtc, stat); break; \
-	case XFS_BTNUM_BMAP: __XFS_BTREE_STATS_INC(__mp, bmbt, stat); break; \
-	case XFS_BTNUM_INO: __XFS_BTREE_STATS_INC(__mp, ibt, stat); break; \
-	case XFS_BTNUM_FINO: __XFS_BTREE_STATS_INC(__mp, fibt, stat); break; \
-	case XFS_BTNUM_RMAP: __XFS_BTREE_STATS_INC(__mp, rmap, stat); break; \
-	case XFS_BTNUM_REFC: __XFS_BTREE_STATS_INC(__mp, refcbt, stat); break; \
-	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break;	\
-	}       \
-} while (0)
-
-#define __XFS_BTREE_STATS_ADD(mp, type, stat, val) \
-	XFS_STATS_ADD(mp, xs_ ## type ## _2_ ## stat, val)
-#define XFS_BTREE_STATS_ADD(cur, stat, val)  \
-do {    \
-	struct xfs_mount *__mp = cur->bc_mp; \
-	switch (cur->bc_btnum) {  \
-	case XFS_BTNUM_BNO:	\
-		__XFS_BTREE_STATS_ADD(__mp, abtb, stat, val); break; \
-	case XFS_BTNUM_CNT:	\
-		__XFS_BTREE_STATS_ADD(__mp, abtc, stat, val); break; \
-	case XFS_BTNUM_BMAP:	\
-		__XFS_BTREE_STATS_ADD(__mp, bmbt, stat, val); break; \
-	case XFS_BTNUM_INO:	\
-		__XFS_BTREE_STATS_ADD(__mp, ibt, stat, val); break; \
-	case XFS_BTNUM_FINO:	\
-		__XFS_BTREE_STATS_ADD(__mp, fibt, stat, val); break; \
-	case XFS_BTNUM_RMAP:	\
-		__XFS_BTREE_STATS_ADD(__mp, rmap, stat, val); break; \
-	case XFS_BTNUM_REFC:	\
-		__XFS_BTREE_STATS_ADD(__mp, refcbt, stat, val); break; \
-	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break; \
-	}       \
-} while (0)
+	XFS_STATS_INC_OFF((cur)->bc_mp, (cur)->bc_statoff + __XBTS_ ## stat)
+#define XFS_BTREE_STATS_ADD(cur, stat, val)	\
+	XFS_STATS_ADD_OFF((cur)->bc_mp, (cur)->bc_statoff + __XBTS_ ## stat, val)
 
 #define	XFS_BTREE_MAXLEVELS	9	/* max of all btrees */
 
@@ -253,6 +217,7 @@ typedef struct xfs_btree_cur
 	__uint8_t	bc_nlevels;	/* number of levels in the tree */
 	__uint8_t	bc_blocklog;	/* log2(blocksize) of btree blocks */
 	xfs_btnum_t	bc_btnum;	/* identifies which btree type */
+	int		bc_statoff;	/* offset of btre stats array */
 	union {
 		struct {			/* needed for BNO, CNT, INO */
 			struct xfs_buf	*agbp;	/* agf/agi buffer pointer */
diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
index eab68ae2e011..e7ff8ef0e5a7 100644
--- a/fs/xfs/libxfs/xfs_ialloc_btree.c
+++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
@@ -365,9 +365,11 @@ xfs_inobt_init_cursor(
 	if (btnum == XFS_BTNUM_INO) {
 		cur->bc_nlevels = be32_to_cpu(agi->agi_level);
 		cur->bc_ops = &xfs_inobt_ops;
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_ibt_2);
 	} else {
 		cur->bc_nlevels = be32_to_cpu(agi->agi_free_level);
 		cur->bc_ops = &xfs_finobt_ops;
+		cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_fibt_2);
 	}
 
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c
index 453bb2757ec2..6fb2215f8ff7 100644
--- a/fs/xfs/libxfs/xfs_refcount_btree.c
+++ b/fs/xfs/libxfs/xfs_refcount_btree.c
@@ -354,6 +354,7 @@ xfs_refcountbt_init_cursor(
 	cur->bc_btnum = XFS_BTNUM_REFC;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
 	cur->bc_ops = &xfs_refcountbt_ops;
+	cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_refcbt_2);
 
 	cur->bc_nlevels = be32_to_cpu(agf->agf_refcount_level);
 
diff --git a/fs/xfs/libxfs/xfs_rmap_btree.c b/fs/xfs/libxfs/xfs_rmap_btree.c
index 83e672ff7577..de25771764ba 100644
--- a/fs/xfs/libxfs/xfs_rmap_btree.c
+++ b/fs/xfs/libxfs/xfs_rmap_btree.c
@@ -484,6 +484,7 @@ xfs_rmapbt_init_cursor(
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
 	cur->bc_ops = &xfs_rmapbt_ops;
 	cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
+	cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_rmap_2);
 
 	cur->bc_private.a.agbp = agbp;
 	cur->bc_private.a.agno = agno;
diff --git a/fs/xfs/xfs_stats.c b/fs/xfs/xfs_stats.c
index 12d48cd8f8a4..f11282c96887 100644
--- a/fs/xfs/xfs_stats.c
+++ b/fs/xfs/xfs_stats.c
@@ -80,9 +80,9 @@ int xfs_stats_format(struct xfsstats __percpu *stats, char *buf)
 	}
 	/* extra precision counters */
 	for_each_possible_cpu(i) {
-		xs_xstrat_bytes += per_cpu_ptr(stats, i)->xs_xstrat_bytes;
-		xs_write_bytes += per_cpu_ptr(stats, i)->xs_write_bytes;
-		xs_read_bytes += per_cpu_ptr(stats, i)->xs_read_bytes;
+		xs_xstrat_bytes += per_cpu_ptr(stats, i)->s.xs_xstrat_bytes;
+		xs_write_bytes += per_cpu_ptr(stats, i)->s.xs_write_bytes;
+		xs_read_bytes += per_cpu_ptr(stats, i)->s.xs_read_bytes;
 	}
 
 	len += snprintf(buf + len, PATH_MAX-len, "xpc %Lu %Lu %Lu\n",
@@ -106,9 +106,9 @@ void xfs_stats_clearall(struct xfsstats __percpu *stats)
 	for_each_possible_cpu(c) {
 		preempt_disable();
 		/* save vn_active, it's a universal truth! */
-		vn_active = per_cpu_ptr(stats, c)->vn_active;
+		vn_active = per_cpu_ptr(stats, c)->s.vn_active;
 		memset(per_cpu_ptr(stats, c), 0, sizeof(*stats));
-		per_cpu_ptr(stats, c)->vn_active = vn_active;
+		per_cpu_ptr(stats, c)->s.vn_active = vn_active;
 		preempt_enable();
 	}
 }
diff --git a/fs/xfs/xfs_stats.h b/fs/xfs/xfs_stats.h
index 79ad2e69fc33..a8725c64091f 100644
--- a/fs/xfs/xfs_stats.h
+++ b/fs/xfs/xfs_stats.h
@@ -21,10 +21,30 @@
 
 #include <linux/percpu.h>
 
+enum {
+	__XBTS_lookup = 0,
+	__XBTS_compare = 1,
+	__XBTS_insrec = 2,
+	__XBTS_delrec = 3,
+	__XBTS_newroot = 4,
+	__XBTS_killroot = 5,
+	__XBTS_increment = 6,
+	__XBTS_decrement = 7,
+	__XBTS_lshift = 8,
+	__XBTS_rshift = 9,
+	__XBTS_split = 10,
+	__XBTS_join = 11,
+	__XBTS_alloc = 12,
+	__XBTS_free = 13,
+	__XBTS_moves = 14,
+
+	__XBTS_MAX = 15,
+};
+
 /*
  * XFS global statistics
  */
-struct xfsstats {
+struct __xfsstats {
 # define XFSSTAT_END_EXTENT_ALLOC	4
 	__uint32_t		xs_allocx;
 	__uint32_t		xs_allocb;
@@ -117,118 +137,20 @@ struct xfsstats {
 	__uint32_t		xb_page_found;
 	__uint32_t		xb_get_read;
 /* Version 2 btree counters */
-#define XFSSTAT_END_ABTB_V2		(XFSSTAT_END_BUF+15)
-	__uint32_t		xs_abtb_2_lookup;
-	__uint32_t		xs_abtb_2_compare;
-	__uint32_t		xs_abtb_2_insrec;
-	__uint32_t		xs_abtb_2_delrec;
-	__uint32_t		xs_abtb_2_newroot;
-	__uint32_t		xs_abtb_2_killroot;
-	__uint32_t		xs_abtb_2_increment;
-	__uint32_t		xs_abtb_2_decrement;
-	__uint32_t		xs_abtb_2_lshift;
-	__uint32_t		xs_abtb_2_rshift;
-	__uint32_t		xs_abtb_2_split;
-	__uint32_t		xs_abtb_2_join;
-	__uint32_t		xs_abtb_2_alloc;
-	__uint32_t		xs_abtb_2_free;
-	__uint32_t		xs_abtb_2_moves;
-#define XFSSTAT_END_ABTC_V2		(XFSSTAT_END_ABTB_V2+15)
-	__uint32_t		xs_abtc_2_lookup;
-	__uint32_t		xs_abtc_2_compare;
-	__uint32_t		xs_abtc_2_insrec;
-	__uint32_t		xs_abtc_2_delrec;
-	__uint32_t		xs_abtc_2_newroot;
-	__uint32_t		xs_abtc_2_killroot;
-	__uint32_t		xs_abtc_2_increment;
-	__uint32_t		xs_abtc_2_decrement;
-	__uint32_t		xs_abtc_2_lshift;
-	__uint32_t		xs_abtc_2_rshift;
-	__uint32_t		xs_abtc_2_split;
-	__uint32_t		xs_abtc_2_join;
-	__uint32_t		xs_abtc_2_alloc;
-	__uint32_t		xs_abtc_2_free;
-	__uint32_t		xs_abtc_2_moves;
-#define XFSSTAT_END_BMBT_V2		(XFSSTAT_END_ABTC_V2+15)
-	__uint32_t		xs_bmbt_2_lookup;
-	__uint32_t		xs_bmbt_2_compare;
-	__uint32_t		xs_bmbt_2_insrec;
-	__uint32_t		xs_bmbt_2_delrec;
-	__uint32_t		xs_bmbt_2_newroot;
-	__uint32_t		xs_bmbt_2_killroot;
-	__uint32_t		xs_bmbt_2_increment;
-	__uint32_t		xs_bmbt_2_decrement;
-	__uint32_t		xs_bmbt_2_lshift;
-	__uint32_t		xs_bmbt_2_rshift;
-	__uint32_t		xs_bmbt_2_split;
-	__uint32_t		xs_bmbt_2_join;
-	__uint32_t		xs_bmbt_2_alloc;
-	__uint32_t		xs_bmbt_2_free;
-	__uint32_t		xs_bmbt_2_moves;
-#define XFSSTAT_END_IBT_V2		(XFSSTAT_END_BMBT_V2+15)
-	__uint32_t		xs_ibt_2_lookup;
-	__uint32_t		xs_ibt_2_compare;
-	__uint32_t		xs_ibt_2_insrec;
-	__uint32_t		xs_ibt_2_delrec;
-	__uint32_t		xs_ibt_2_newroot;
-	__uint32_t		xs_ibt_2_killroot;
-	__uint32_t		xs_ibt_2_increment;
-	__uint32_t		xs_ibt_2_decrement;
-	__uint32_t		xs_ibt_2_lshift;
-	__uint32_t		xs_ibt_2_rshift;
-	__uint32_t		xs_ibt_2_split;
-	__uint32_t		xs_ibt_2_join;
-	__uint32_t		xs_ibt_2_alloc;
-	__uint32_t		xs_ibt_2_free;
-	__uint32_t		xs_ibt_2_moves;
-#define XFSSTAT_END_FIBT_V2		(XFSSTAT_END_IBT_V2+15)
-	__uint32_t		xs_fibt_2_lookup;
-	__uint32_t		xs_fibt_2_compare;
-	__uint32_t		xs_fibt_2_insrec;
-	__uint32_t		xs_fibt_2_delrec;
-	__uint32_t		xs_fibt_2_newroot;
-	__uint32_t		xs_fibt_2_killroot;
-	__uint32_t		xs_fibt_2_increment;
-	__uint32_t		xs_fibt_2_decrement;
-	__uint32_t		xs_fibt_2_lshift;
-	__uint32_t		xs_fibt_2_rshift;
-	__uint32_t		xs_fibt_2_split;
-	__uint32_t		xs_fibt_2_join;
-	__uint32_t		xs_fibt_2_alloc;
-	__uint32_t		xs_fibt_2_free;
-	__uint32_t		xs_fibt_2_moves;
-#define XFSSTAT_END_RMAP_V2		(XFSSTAT_END_FIBT_V2+15)
-	__uint32_t		xs_rmap_2_lookup;
-	__uint32_t		xs_rmap_2_compare;
-	__uint32_t		xs_rmap_2_insrec;
-	__uint32_t		xs_rmap_2_delrec;
-	__uint32_t		xs_rmap_2_newroot;
-	__uint32_t		xs_rmap_2_killroot;
-	__uint32_t		xs_rmap_2_increment;
-	__uint32_t		xs_rmap_2_decrement;
-	__uint32_t		xs_rmap_2_lshift;
-	__uint32_t		xs_rmap_2_rshift;
-	__uint32_t		xs_rmap_2_split;
-	__uint32_t		xs_rmap_2_join;
-	__uint32_t		xs_rmap_2_alloc;
-	__uint32_t		xs_rmap_2_free;
-	__uint32_t		xs_rmap_2_moves;
-#define XFSSTAT_END_REFCOUNT		(XFSSTAT_END_RMAP_V2 + 15)
-	__uint32_t		xs_refcbt_2_lookup;
-	__uint32_t		xs_refcbt_2_compare;
-	__uint32_t		xs_refcbt_2_insrec;
-	__uint32_t		xs_refcbt_2_delrec;
-	__uint32_t		xs_refcbt_2_newroot;
-	__uint32_t		xs_refcbt_2_killroot;
-	__uint32_t		xs_refcbt_2_increment;
-	__uint32_t		xs_refcbt_2_decrement;
-	__uint32_t		xs_refcbt_2_lshift;
-	__uint32_t		xs_refcbt_2_rshift;
-	__uint32_t		xs_refcbt_2_split;
-	__uint32_t		xs_refcbt_2_join;
-	__uint32_t		xs_refcbt_2_alloc;
-	__uint32_t		xs_refcbt_2_free;
-	__uint32_t		xs_refcbt_2_moves;
+#define XFSSTAT_END_ABTB_V2		(XFSSTAT_END_BUF + __XBTS_MAX)
+	__uint32_t		xs_abtb_2[__XBTS_MAX];
+#define XFSSTAT_END_ABTC_V2		(XFSSTAT_END_ABTB_V2 + __XBTS_MAX)
+	__uint32_t		xs_abtc_2[__XBTS_MAX];
+#define XFSSTAT_END_BMBT_V2		(XFSSTAT_END_ABTC_V2 + __XBTS_MAX)
+	__uint32_t		xs_bmbt_2[__XBTS_MAX];
+#define XFSSTAT_END_IBT_V2		(XFSSTAT_END_BMBT_V2 + __XBTS_MAX)
+	__uint32_t		xs_ibt_2[__XBTS_MAX];
+#define XFSSTAT_END_FIBT_V2		(XFSSTAT_END_IBT_V2 + __XBTS_MAX)
+	__uint32_t		xs_fibt_2[__XBTS_MAX];
+#define XFSSTAT_END_RMAP_V2		(XFSSTAT_END_FIBT_V2 + __XBTS_MAX)
+	__uint32_t		xs_rmap_2[__XBTS_MAX];
+#define XFSSTAT_END_REFCOUNT		(XFSSTAT_END_RMAP_V2 + __XBTS_MAX)
+	__uint32_t		xs_refcbt_2[__XBTS_MAX];
 #define XFSSTAT_END_XQMSTAT		(XFSSTAT_END_REFCOUNT + 6)
 	__uint32_t		xs_qm_dqreclaims;
 	__uint32_t		xs_qm_dqreclaim_misses;
@@ -245,26 +167,58 @@ struct xfsstats {
 	__uint64_t		xs_read_bytes;
 };
 
+struct xfsstats {
+	union {
+		struct __xfsstats	s;
+		uint32_t		a[XFSSTAT_END_XQMSTAT];
+	};
+};
+
+/*
+ * simple wrapper for getting the array index of s struct member offset
+ */
+#define XFS_STATS_CALC_INDEX(member)	\
+	(offsetof(struct __xfsstats, member) / (int)sizeof(__uint32_t))
+
+
 int xfs_stats_format(struct xfsstats __percpu *stats, char *buf);
 void xfs_stats_clearall(struct xfsstats __percpu *stats);
 extern struct xstats xfsstats;
 
 #define XFS_STATS_INC(mp, v)					\
 do {								\
-	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->v++;	\
-	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->v++;	\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->s.v++;	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->s.v++;	\
 } while (0)
 
 #define XFS_STATS_DEC(mp, v)					\
 do {								\
-	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->v--;	\
-	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->v--;	\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->s.v--;	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->s.v--;	\
 } while (0)
 
 #define XFS_STATS_ADD(mp, v, inc)					\
 do {									\
-	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->v += (inc);	\
-	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->v += (inc);	\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->s.v += (inc);	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->s.v += (inc);	\
+} while (0)
+
+#define XFS_STATS_INC_OFF(mp, off)				\
+do {								\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->a[off]++;	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->a[off]++;	\
+} while (0)
+
+#define XFS_STATS_DEC_OFF(mp, off)					\
+do {								\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->a[off];	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->a[off];	\
+} while (0)
+
+#define XFS_STATS_ADD_OFF(mp, off, inc)					\
+do {									\
+	per_cpu_ptr(xfsstats.xs_stats, current_cpu())->a[off] += (inc);	\
+	per_cpu_ptr(mp->m_stats.xs_stats, current_cpu())->a[off] += (inc);	\
 } while (0)
 
 #if defined(CONFIG_PROC_FS)
-- 
2.10.2

[PATCH 2/3] xfs: use rhashtable to track buffer cache

[Dave Chinner]

From: Lucas Stach <dev@lynxeye.de>

On filesystems with a lot of metadata and in metadata intensive workloads
xfs_buf_find() is showing up at the top of the CPU cycles trace. Most of
the CPU time is spent on CPU cache misses while traversing the rbtree.

As the buffer cache does not need any kind of ordering, but fast lookups
a hashtable is the natural data structure to use. The rhashtable
infrastructure provides a self-scaling hashtable implementation and
allows lookups to proceed while the table is going through a resize
operation.

This reduces the CPU-time spent for the lookups to 1/3 even for small
filesystems with a relatively small number of cached buffers, with
possibly much larger gains on higher loaded filesystems.

[dchinner: reduce minimum hash size to an acceptable size for large
	   filesystems with many AGs with no active use.]
[dchinner: remove stale rbtree asserts.]
[dchinner: use xfs_buf_map for compare function argument.]
[dchinner: make functions static.]
[dchinner: remove redundant comments.]

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_buf.c   | 121 ++++++++++++++++++++++++++++++++---------------------
 fs/xfs/xfs_buf.h   |   2 +-
 fs/xfs/xfs_linux.h |   1 +
 fs/xfs/xfs_mount.c |   7 +++-
 fs/xfs/xfs_mount.h |   7 +++-
 5 files changed, 86 insertions(+), 52 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index b5b9bffe3520..a2f0648743db 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -219,7 +219,6 @@ _xfs_buf_alloc(
 	init_completion(&bp->b_iowait);
 	INIT_LIST_HEAD(&bp->b_lru);
 	INIT_LIST_HEAD(&bp->b_list);
-	RB_CLEAR_NODE(&bp->b_rbnode);
 	sema_init(&bp->b_sema, 0); /* held, no waiters */
 	spin_lock_init(&bp->b_lock);
 	XB_SET_OWNER(bp);
@@ -473,6 +472,63 @@ _xfs_buf_map_pages(
 /*
  *	Finding and Reading Buffers
  */
+static int
+_xfs_buf_cmp(
+	struct rhashtable_compare_arg *arg,
+	const void *obj)
+{
+	const struct xfs_buf_map *map = arg->key;
+	const struct xfs_buf *bp = obj;
+
+	/*
+	 * The key hashing in the lookup path depends on the key being the
+	 * first element of the compare_arg, make sure to assert this.
+	 */
+	BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
+
+	if (bp->b_bn == map->bm_bn) {
+		if (unlikely(bp->b_length != map->bm_len)) {
+			/*
+			 * found a block number match. If the range doesn't
+			 * match, the only way this is allowed is if the buffer
+			 * in the cache is stale and the transaction that made
+			 * it stale has not yet committed. i.e. we are
+			 * reallocating a busy extent. Skip this buffer and
+			 * continue searching for an exact match.
+			 */
+			ASSERT(bp->b_flags & XBF_STALE);
+			return 1;
+		}
+
+		return 0;
+	}
+
+	return 1;
+}
+
+static const struct rhashtable_params xfs_buf_hash_params = {
+	.min_size = 32,		/* empty/unused AGs have minimal footprint */
+	.nelem_hint = 16,
+	.key_len = sizeof(xfs_daddr_t),
+	.key_offset = offsetof(struct xfs_buf, b_bn),
+	.head_offset = offsetof(struct xfs_buf, b_rhash_head),
+	.automatic_shrinking = true,
+	.obj_cmpfn = _xfs_buf_cmp,
+};
+
+int xfs_buf_hash_init(
+	struct xfs_perag *pag)
+{
+	spin_lock_init(&pag->pag_buf_lock);
+	return rhashtable_init(&pag->pag_buf_hash, &xfs_buf_hash_params);
+}
+
+void
+xfs_buf_hash_destroy(
+	struct xfs_perag *pag)
+{
+	rhashtable_destroy(&pag->pag_buf_hash);
+}
 
 /*
  *	Look up, and creates if absent, a lockable buffer for
@@ -488,27 +544,24 @@ _xfs_buf_find(
 	xfs_buf_t		*new_bp)
 {
 	struct xfs_perag	*pag;
-	struct rb_node		**rbp;
-	struct rb_node		*parent;
 	xfs_buf_t		*bp;
-	xfs_daddr_t		blkno = map[0].bm_bn;
+	struct xfs_buf_map	cmap = { .bm_bn = map[0].bm_bn };
 	xfs_daddr_t		eofs;
-	int			numblks = 0;
 	int			i;
 
 	for (i = 0; i < nmaps; i++)
-		numblks += map[i].bm_len;
+		cmap.bm_len += map[i].bm_len;
 
 	/* Check for IOs smaller than the sector size / not sector aligned */
-	ASSERT(!(BBTOB(numblks) < btp->bt_meta_sectorsize));
-	ASSERT(!(BBTOB(blkno) & (xfs_off_t)btp->bt_meta_sectormask));
+	ASSERT(!(BBTOB(cmap.bm_len) < btp->bt_meta_sectorsize));
+	ASSERT(!(BBTOB(cmap.bm_bn) & (xfs_off_t)btp->bt_meta_sectormask));
 
 	/*
 	 * Corrupted block numbers can get through to here, unfortunately, so we
 	 * have to check that the buffer falls within the filesystem bounds.
 	 */
 	eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
-	if (blkno < 0 || blkno >= eofs) {
+	if (cmap.bm_bn < 0 || cmap.bm_bn >= eofs) {
 		/*
 		 * XXX (dgc): we should really be returning -EFSCORRUPTED here,
 		 * but none of the higher level infrastructure supports
@@ -516,53 +569,29 @@ _xfs_buf_find(
 		 */
 		xfs_alert(btp->bt_mount,
 			  "%s: Block out of range: block 0x%llx, EOFS 0x%llx ",
-			  __func__, blkno, eofs);
+			  __func__, cmap.bm_bn, eofs);
 		WARN_ON(1);
 		return NULL;
 	}
 
-	/* get tree root */
 	pag = xfs_perag_get(btp->bt_mount,
-				xfs_daddr_to_agno(btp->bt_mount, blkno));
+			    xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
 
-	/* walk tree */
 	spin_lock(&pag->pag_buf_lock);
-	rbp = &pag->pag_buf_tree.rb_node;
-	parent = NULL;
-	bp = NULL;
-	while (*rbp) {
-		parent = *rbp;
-		bp = rb_entry(parent, struct xfs_buf, b_rbnode);
-
-		if (blkno < bp->b_bn)
-			rbp = &(*rbp)->rb_left;
-		else if (blkno > bp->b_bn)
-			rbp = &(*rbp)->rb_right;
-		else {
-			/*
-			 * found a block number match. If the range doesn't
-			 * match, the only way this is allowed is if the buffer
-			 * in the cache is stale and the transaction that made
-			 * it stale has not yet committed. i.e. we are
-			 * reallocating a busy extent. Skip this buffer and
-			 * continue searching to the right for an exact match.
-			 */
-			if (bp->b_length != numblks) {
-				ASSERT(bp->b_flags & XBF_STALE);
-				rbp = &(*rbp)->rb_right;
-				continue;
-			}
-			atomic_inc(&bp->b_hold);
-			goto found;
-		}
+	bp = rhashtable_lookup_fast(&pag->pag_buf_hash, &cmap,
+				    xfs_buf_hash_params);
+	if (bp) {
+		atomic_inc(&bp->b_hold);
+		goto found;
 	}
 
 	/* No match found */
 	if (new_bp) {
-		rb_link_node(&new_bp->b_rbnode, parent, rbp);
-		rb_insert_color(&new_bp->b_rbnode, &pag->pag_buf_tree);
 		/* the buffer keeps the perag reference until it is freed */
 		new_bp->b_pag = pag;
+		rhashtable_insert_fast(&pag->pag_buf_hash,
+				       &new_bp->b_rhash_head,
+				       xfs_buf_hash_params);
 		spin_unlock(&pag->pag_buf_lock);
 	} else {
 		XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
@@ -930,7 +959,6 @@ xfs_buf_rele(
 
 	if (!pag) {
 		ASSERT(list_empty(&bp->b_lru));
-		ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
 		if (atomic_dec_and_test(&bp->b_hold)) {
 			xfs_buf_ioacct_dec(bp);
 			xfs_buf_free(bp);
@@ -938,8 +966,6 @@ xfs_buf_rele(
 		return;
 	}
 
-	ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
-
 	ASSERT(atomic_read(&bp->b_hold) > 0);
 
 	release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
@@ -983,7 +1009,8 @@ xfs_buf_rele(
 		}
 
 		ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
-		rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
+		rhashtable_remove_fast(&pag->pag_buf_hash, &bp->b_rhash_head,
+				       xfs_buf_hash_params);
 		spin_unlock(&pag->pag_buf_lock);
 		xfs_perag_put(pag);
 		freebuf = true;
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 38c9a95bda7d..8a9d3a9599f0 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -151,7 +151,7 @@ typedef struct xfs_buf {
 	 * which is the only bit that is touched if we hit the semaphore
 	 * fast-path on locking.
 	 */
-	struct rb_node		b_rbnode;	/* rbtree node */
+	struct rhash_head	b_rhash_head;	/* pag buffer hash node */
 	xfs_daddr_t		b_bn;		/* block number of buffer */
 	int			b_length;	/* size of buffer in BBs */
 	atomic_t		b_hold;		/* reference count */
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 68640fb63a54..a415f822f2c1 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -78,6 +78,7 @@ typedef __u32			xfs_nlink_t;
 #include <linux/freezer.h>
 #include <linux/list_sort.h>
 #include <linux/ratelimit.h>
+#include <linux/rhashtable.h>
 
 #include <asm/page.h>
 #include <asm/div64.h>
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index b341f10cf481..9b9540db17a6 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -157,6 +157,7 @@ xfs_free_perag(
 		spin_unlock(&mp->m_perag_lock);
 		ASSERT(pag);
 		ASSERT(atomic_read(&pag->pag_ref) == 0);
+		xfs_buf_hash_destroy(pag);
 		call_rcu(&pag->rcu_head, __xfs_free_perag);
 	}
 }
@@ -212,8 +213,8 @@ xfs_initialize_perag(
 		spin_lock_init(&pag->pag_ici_lock);
 		mutex_init(&pag->pag_ici_reclaim_lock);
 		INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
-		spin_lock_init(&pag->pag_buf_lock);
-		pag->pag_buf_tree = RB_ROOT;
+		if (xfs_buf_hash_init(pag))
+			goto out_unwind;
 
 		if (radix_tree_preload(GFP_NOFS))
 			goto out_unwind;
@@ -239,9 +240,11 @@ xfs_initialize_perag(
 	return 0;
 
 out_unwind:
+	xfs_buf_hash_destroy(pag);
 	kmem_free(pag);
 	for (; index > first_initialised; index--) {
 		pag = radix_tree_delete(&mp->m_perag_tree, index);
+		xfs_buf_hash_destroy(pag);
 		kmem_free(pag);
 	}
 	return error;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 819b80b15bfb..84f785218907 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -393,8 +393,8 @@ typedef struct xfs_perag {
 	unsigned long	pag_ici_reclaim_cursor;	/* reclaim restart point */
 
 	/* buffer cache index */
-	spinlock_t	pag_buf_lock;	/* lock for pag_buf_tree */
-	struct rb_root	pag_buf_tree;	/* ordered tree of active buffers */
+	spinlock_t	pag_buf_lock;	/* lock for pag_buf_hash */
+	struct rhashtable pag_buf_hash;
 
 	/* for rcu-safe freeing */
 	struct rcu_head	rcu_head;
@@ -424,6 +424,9 @@ xfs_perag_resv(
 	}
 }
 
+int xfs_buf_hash_init(xfs_perag_t *pag);
+void xfs_buf_hash_destroy(xfs_perag_t *pag);
+
 extern void	xfs_uuid_table_free(void);
 extern int	xfs_log_sbcount(xfs_mount_t *);
 extern __uint64_t xfs_default_resblks(xfs_mount_t *mp);
-- 
2.10.2

[PATCH 3/3] xfs: optimise CRC updates

[Dave Chinner]

From: Dave Chinner <dchinner@redhat.com>

Nick Piggin reported that the CRC overhead in an fsync heavy
workload was higher than expected on a Power8 machine. Part of this
was to do with the fact that the power8 CRC implementation is not
efficient for CRC lengths of less than 512 bytes, and so the way we
split the CRCs over the CRC field means a lot of the CRCs are
reduced to being less than than optimal size.

TO otpimise this, change the CRC update mechanism to zero the CRC
field first, and then compute the CRC in one pass over the buffer
and write the result back into the buffer. We can do this safely
because anything writing a CRC has exclusive access to the buffer
the CRC is being calculated over.

We leave the CRC verify code the same - it still splits the CRC
calculation - because we do not want read-only operations modifying
the underlying buffer. This is because read-only operations may not
have an exclusive access to the buffer guaranteed, and so temporary
modifications could leak out to to other processes accessing the
buffer concurrently.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/libxfs/xfs_cksum.h     | 26 ++++++++++++++++++++++----
 fs/xfs/libxfs/xfs_inode_buf.c |  2 +-
 fs/xfs/xfs_log.c              |  2 +-
 fs/xfs/xfs_log_recover.c      | 12 +++++++-----
 4 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_cksum.h b/fs/xfs/libxfs/xfs_cksum.h
index fad1676ad8cd..a416c7cb23ea 100644
--- a/fs/xfs/libxfs/xfs_cksum.h
+++ b/fs/xfs/libxfs/xfs_cksum.h
@@ -6,10 +6,11 @@
 /*
  * Calculate the intermediate checksum for a buffer that has the CRC field
  * inside it.  The offset of the 32bit crc fields is passed as the
- * cksum_offset parameter.
+ * cksum_offset parameter. We do not modify the buffer during verification,
+ * hence we have to split the CRC calculation across the cksum_offset.
  */
 static inline __uint32_t
-xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
+xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
 {
 	__uint32_t zero = 0;
 	__uint32_t crc;
@@ -26,6 +27,20 @@ xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
 }
 
 /*
+ * Fast CRC method where the buffer is modified. Callers must have exclusive
+ * access to the buffer while the calculation takes place.
+ */
+static inline __uint32_t
+xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
+{
+	/* zero the CRC field */
+	*(__le32 *)(buffer + cksum_offset) = 0;
+
+	/* single pass CRC calculation for the entire buffer */
+	return crc32c(XFS_CRC_SEED, buffer, length);
+}
+
+/*
  * Convert the intermediate checksum to the final ondisk format.
  *
  * The CRC32c calculation uses LE format even on BE machines, but returns the
@@ -40,11 +55,14 @@ xfs_end_cksum(__uint32_t crc)
 
 /*
  * Helper to generate the checksum for a buffer.
+ *
+ * This modifies the buffer temporarily - callers must have exclusive
+ * access to the buffer while the calculation takes place.
  */
 static inline void
 xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
 {
-	__uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
+	__uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);
 
 	*(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
 }
@@ -55,7 +73,7 @@ xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
 static inline int
 xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
 {
-	__uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
+	__uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);
 
 	return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
 }
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 54817f82212c..5efeb4233387 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -436,7 +436,7 @@ xfs_dinode_calc_crc(
 		return;
 
 	ASSERT(xfs_sb_version_hascrc(&mp->m_sb));
-	crc = xfs_start_cksum((char *)dip, mp->m_sb.sb_inodesize,
+	crc = xfs_start_cksum_update((char *)dip, mp->m_sb.sb_inodesize,
 			      XFS_DINODE_CRC_OFF);
 	dip->di_crc = xfs_end_cksum(crc);
 }
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 3b74fa011bb1..3ebe444eb60f 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1668,7 +1668,7 @@ xlog_cksum(
 	__uint32_t		crc;
 
 	/* first generate the crc for the record header ... */
-	crc = xfs_start_cksum((char *)rhead,
+	crc = xfs_start_cksum_update((char *)rhead,
 			      sizeof(struct xlog_rec_header),
 			      offsetof(struct xlog_rec_header, h_crc));
 
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index cf754bcbcb1c..4a98762ec8b4 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -5113,19 +5113,21 @@ xlog_recover_process(
 	struct list_head	*buffer_list)
 {
 	int			error;
+	__le32			old_crc = rhead->h_crc;
 	__le32			crc;
 
+
 	crc = xlog_cksum(log, rhead, dp, be32_to_cpu(rhead->h_len));
 
 	/*
 	 * Nothing else to do if this is a CRC verification pass. Just return
 	 * if this a record with a non-zero crc. Unfortunately, mkfs always
-	 * sets h_crc to 0 so we must consider this valid even on v5 supers.
+	 * sets old_crc to 0 so we must consider this valid even on v5 supers.
 	 * Otherwise, return EFSBADCRC on failure so the callers up the stack
 	 * know precisely what failed.
 	 */
 	if (pass == XLOG_RECOVER_CRCPASS) {
-		if (rhead->h_crc && crc != rhead->h_crc)
+		if (old_crc && crc != old_crc)
 			return -EFSBADCRC;
 		return 0;
 	}
@@ -5136,11 +5138,11 @@ xlog_recover_process(
 	 * zero CRC check prevents warnings from being emitted when upgrading
 	 * the kernel from one that does not add CRCs by default.
 	 */
-	if (crc != rhead->h_crc) {
-		if (rhead->h_crc || xfs_sb_version_hascrc(&log->l_mp->m_sb)) {
+	if (crc != old_crc) {
+		if (old_crc || xfs_sb_version_hascrc(&log->l_mp->m_sb)) {
 			xfs_alert(log->l_mp,
 		"log record CRC mismatch: found 0x%x, expected 0x%x.",
-					le32_to_cpu(rhead->h_crc),
+					le32_to_cpu(old_crc),
 					le32_to_cpu(crc));
 			xfs_hex_dump(dp, 32);
 		}
-- 
2.10.2

Re: [PATCH 1/3] xfs: make xfs btree stats less huge

[Christoph Hellwig]

> --- a/fs/xfs/xfs_stats.h
> +++ b/fs/xfs/xfs_stats.h
> @@ -21,10 +21,30 @@
>  
>  #include <linux/percpu.h>
>  
> +enum {
> +	__XBTS_lookup = 0,

Add a comment on top of the enum to explain these are the
offsets into each btree type?

> +#define XFS_STATS_CALC_INDEX(member)	\
> +	(offsetof(struct __xfsstats, member) / (int)sizeof(__uint32_t))

what's that int cast for?

Except for these nitpicks this looks great:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 3/3] xfs: optimise CRC updates

[Christoph Hellwig]

> +xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)

> +xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)

What about turning the first argument into a void * for both so that
we can avoid all the pointless casts?

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 3/3] xfs: optimise CRC updates

[Dave Chinner]

On Fri, Dec 02, 2016 at 05:22:45AM -0800, Christoph Hellwig wrote:
> > +xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
> 
> > +xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
> 
> What about turning the first argument into a void * for both so that
> we can avoid all the pointless casts?

I thought the C standard specifically disallowed pointer arithmetic
on void pointers because they are an incomplete type, even though
they have the same alignment/representation as a char *.

IIRC, gcc will throw errors on such code if -pedantic-errors or
-Werror-pointer-arith is specified...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [PATCH 1/3] xfs: make xfs btree stats less huge

[Dave Chinner]

On Fri, Dec 02, 2016 at 05:20:44AM -0800, Christoph Hellwig wrote:
> 
> > --- a/fs/xfs/xfs_stats.h
> > +++ b/fs/xfs/xfs_stats.h
> > @@ -21,10 +21,30 @@
> >  
> >  #include <linux/percpu.h>
> >  
> > +enum {
> > +	__XBTS_lookup = 0,
> 
> Add a comment on top of the enum to explain these are the
> offsets into each btree type?

Will do.

> > +#define XFS_STATS_CALC_INDEX(member)	\
> > +	(offsetof(struct __xfsstats, member) / (int)sizeof(__uint32_t))
> 
> what's that int cast for?

Habit - prevents 64 bit division on 32 bit systems. But given this
is evaluated at compile time, that doesn't matter. Will remove.

> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks!

-- 
Dave Chinner
david@fromorbit.com

Re: [PATCH 1/3] xfs: make xfs btree stats less huge

[Christoph Hellwig]

On Mon, Dec 05, 2016 at 12:14:32PM +1100, Dave Chinner wrote:
> > > +	(offsetof(struct __xfsstats, member) / (int)sizeof(__uint32_t))
> > 
> > what's that int cast for?
> 
> Habit - prevents 64 bit division on 32 bit systems. But given this
> is evaluated at compile time, that doesn't matter. Will remove.

sizeof returns a size_t, which at least on Linux will always be
equivalent to an unsigned long, i.e. 32-bit on a 32-bit system, 64-bit
on a 64-bit system.

Re: [PATCH 3/3] xfs: optimise CRC updates

[Christoph Hellwig]

On Mon, Dec 05, 2016 at 09:12:31AM +1100, Dave Chinner wrote:
> I thought the C standard specifically disallowed pointer arithmetic
> on void pointers because they are an incomplete type, even though
> they have the same alignment/representation as a char *.
> 
> IIRC, gcc will throw errors on such code if -pedantic-errors or
> -Werror-pointer-arith is specified...

void pointer arithmetics is a GNU extension indeed, but on that
the kernel relies on heavily.

Re: [PATCH 2/3] xfs: use rhashtable to track buffer cache

[Christoph Hellwig]

> +static int
> +_xfs_buf_cmp(
> +	struct rhashtable_compare_arg *arg,
> +	const void *obj)
> +{
> +	const struct xfs_buf_map *map = arg->key;
> +	const struct xfs_buf *bp = obj;

How about aligning the parameter / variable names here like we
normally do in XFS?

> +static const struct rhashtable_params xfs_buf_hash_params = {
> +	.min_size = 32,		/* empty/unused AGs have minimal footprint */
> +	.nelem_hint = 16,
> +	.key_len = sizeof(xfs_daddr_t),
> +	.key_offset = offsetof(struct xfs_buf, b_bn),
> +	.head_offset = offsetof(struct xfs_buf, b_rhash_head),
> +	.automatic_shrinking = true,
> +	.obj_cmpfn = _xfs_buf_cmp,

Some tab alignments before the equal signs here?

Also please name the compare function so that it fits the field name,
as that makes grepping so much easier..

	.obj_cmpfn	= xfs_buf_obj_cmpfn,


Otherwise this looks fine to me and seems to survive testing so far:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 2/3] xfs: use rhashtable to track buffer cache

[Dave Chinner]

On Mon, Dec 05, 2016 at 09:04:11AM -0800, Christoph Hellwig wrote:
> > +static int
> > +_xfs_buf_cmp(
> > +	struct rhashtable_compare_arg *arg,
> > +	const void *obj)
> > +{
> > +	const struct xfs_buf_map *map = arg->key;
> > +	const struct xfs_buf *bp = obj;
> 
> How about aligning the parameter / variable names here like we
> normally do in XFS?

Sorry, forgot to do that when I updated the patch.

> > +static const struct rhashtable_params xfs_buf_hash_params = {
> > +	.min_size = 32,		/* empty/unused AGs have minimal footprint */
> > +	.nelem_hint = 16,
> > +	.key_len = sizeof(xfs_daddr_t),
> > +	.key_offset = offsetof(struct xfs_buf, b_bn),
> > +	.head_offset = offsetof(struct xfs_buf, b_rhash_head),
> > +	.automatic_shrinking = true,
> > +	.obj_cmpfn = _xfs_buf_cmp,
> 
> Some tab alignments before the equal signs here?
> 
> Also please name the compare function so that it fits the field name,
> as that makes grepping so much easier..
> 
> 	.obj_cmpfn	= xfs_buf_obj_cmpfn,

Will do.

> Otherwise this looks fine to me and seems to survive testing so far:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks.

-Dave.
-- 
Dave Chinner
david@fromorbit.com