Cluster Project branch, STABLE2, updated. cluster-2.03.02-26-gb88e25c

[rpeterso@sourceware.org]

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- Log -----------------------------------------------------------------
commit b88e25c2d3679cf06f3b9c896365b359a29bba0f
Author: Bob Peterson <rpeterso@redhat.com>
Date:   Tue May 20 09:37:53 2008 -0500

    bz 446085: Back-port faster bitfit algorithm from gfs2 for better
    performance.

-----------------------------------------------------------------------

Summary of changes:
 gfs-kernel/src/gfs/bits.c |   85 +++++++++++++++++++++++++++++++-------------
 gfs-kernel/src/gfs/bits.h |    3 +-
 gfs-kernel/src/gfs/rgrp.c |    3 +-
 3 files changed, 62 insertions(+), 29 deletions(-)

diff --git a/gfs-kernel/src/gfs/bits.c b/gfs-kernel/src/gfs/bits.c
index da08a23..55427bb 100644
--- a/gfs-kernel/src/gfs/bits.c
+++ b/gfs-kernel/src/gfs/bits.c
@@ -31,6 +31,16 @@
 #include "gfs.h"
 #include "bits.h"
 
+#if BITS_PER_LONG == 32
+#define LBITMASK   (0x55555555UL)
+#define LBITSKIP55 (0x55555555UL)
+#define LBITSKIP00 (0x00000000UL)
+#else
+#define LBITMASK   (0x5555555555555555UL)
+#define LBITSKIP55 (0x5555555555555555UL)
+#define LBITSKIP00 (0x0000000000000000UL)
+#endif
+
 static const char valid_change[16] = {
 	        /* current */
 	/* n */ 0, 1, 1, 1,
@@ -115,41 +125,66 @@ gfs_testbit(struct gfs_rgrpd *rgd,
  */
 
 uint32_t
-gfs_bitfit(struct gfs_rgrpd *rgd,
-	   unsigned char *buffer, unsigned int buflen,
+gfs_bitfit(unsigned char *buffer, unsigned int buflen,
 	   uint32_t goal, unsigned char old_state)
 {
-	unsigned char *byte, *end, alloc;
-	uint32_t blk = goal;
-	unsigned int bit;
-
-	byte = buffer + (goal / GFS_NBBY);
-	bit = (goal % GFS_NBBY) * GFS_BIT_SIZE;
-	end = buffer + buflen;
-	alloc = (old_state & 1) ? 0 : 0x55;
-
+	const u8 *byte, *start, *end;
+	int bit, startbit;
+	u32 g1, g2, misaligned;
+	unsigned long *plong;
+	unsigned long lskipval;
+
+	lskipval = (old_state & GFS_BLKST_USED) ? LBITSKIP00 : LBITSKIP55;
+	g1 = (goal / GFS_NBBY);
+	start = buffer + g1;
+	byte = start;
+        end = buffer + buflen;
+	g2 = ALIGN(g1, sizeof(unsigned long));
+	plong = (unsigned long *)(buffer + g2);
+	startbit = bit = (goal % GFS_NBBY) * GFS_BIT_SIZE;
+	misaligned = g2 - g1;
+	if (!misaligned)
+		goto ulong_aligned;
+/* parse the bitmap a byte at a time */
+misaligned:
 	while (byte < end) {
-		if ((*byte & 0x55) == alloc) {
-			blk += (8 - bit) >> 1;
-
-			bit = 0;
-			byte++;
-
-			continue;
+		if (((*byte >> bit) & GFS_BIT_MASK) == old_state) {
+			return goal +
+				(((byte - start) * GFS_NBBY) +
+				 ((bit - startbit) >> 1));
 		}
-
-		if (((*byte >> bit) & GFS_BIT_MASK) == old_state)
-			return blk;
-
 		bit += GFS_BIT_SIZE;
-		if (bit >= 8) {
+		if (bit >= GFS_NBBY * GFS_BIT_SIZE) {
 			bit = 0;
 			byte++;
+			misaligned--;
+			if (!misaligned) {
+				plong = (unsigned long *)byte;
+				goto ulong_aligned;
+			}
 		}
-
-		blk++;
 	}
+	return BFITNOENT;
 
+/* parse the bitmap a unsigned long at a time */
+ulong_aligned:
+	/* Stop at "end - 1" or else prefetch can go past the end and segfault.
+	   We could "if" it but we'd lose some of the performance gained.
+	   This way will only slow down searching the very last 4/8 bytes
+	   depending on architecture.  I've experimented with several ways
+	   of writing this section such as using an else before the goto
+	   but this one seems to be the fastest. */
+	while ((unsigned char *)plong < end - 1) {
+		prefetch(plong + 1);
+		if (((*plong) & LBITMASK) != lskipval)
+			break;
+		plong++;
+	}
+	if ((unsigned char *)plong < end) {
+		byte = (const u8 *)plong;
+		misaligned += sizeof(unsigned long) - 1;
+		goto misaligned;
+	}
 	return BFITNOENT;
 }
 
diff --git a/gfs-kernel/src/gfs/bits.h b/gfs-kernel/src/gfs/bits.h
index ed38102..9990bae 100644
--- a/gfs-kernel/src/gfs/bits.h
+++ b/gfs-kernel/src/gfs/bits.h
@@ -22,8 +22,7 @@ void gfs_setbit(struct gfs_rgrpd *rgd,
 unsigned char gfs_testbit(struct gfs_rgrpd *rgd,
 			  unsigned char *buffer, unsigned int buflen,
 			  uint32_t block);
-uint32_t gfs_bitfit(struct gfs_rgrpd *rgd,
-		    unsigned char *buffer, unsigned int buflen,
+uint32_t gfs_bitfit(unsigned char *buffer, unsigned int buflen,
 		    uint32_t goal, unsigned char old_state);
 uint32_t gfs_bitcount(struct gfs_rgrpd *rgd,
 		      unsigned char *buffer, unsigned int buflen,
diff --git a/gfs-kernel/src/gfs/rgrp.c b/gfs-kernel/src/gfs/rgrp.c
index dd7fdcb..f0a4e3f 100644
--- a/gfs-kernel/src/gfs/rgrp.c
+++ b/gfs-kernel/src/gfs/rgrp.c
@@ -1444,8 +1444,7 @@ blkalloc_internal(struct gfs_rgrpd *rgd,
 	   allocatable block anywhere else, we want to be able wrap around and
 	   search in the first part of our first-searched bit block.  */
 	for (x = 0; x <= length; x++) {
-		blk = gfs_bitfit(rgd,
-				 rgd->rd_bh[buf]->b_data + bits->bi_offset,
+		blk = gfs_bitfit(rgd->rd_bh[buf]->b_data + bits->bi_offset,
 				 bits->bi_len, goal, old_state);
 		if (blk != BFITNOENT)
 			break;


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