[Cluster-devel] [PATCH 02/15] GFS2: Set of distributed preferences for rgrps

[Steven Whitehouse <swhiteho@redhat.com>]

From: Bob Peterson <rpeterso@redhat.com>

This patch tries to use the journal numbers to evenly distribute
which node prefers which resource group for block allocations. This
is to help performance.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 39e7e99..1b89918 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -97,6 +97,7 @@ struct gfs2_rgrpd {
 #define GFS2_RDF_CHECK		0x10000000 /* check for unlinked inodes */
 #define GFS2_RDF_UPTODATE	0x20000000 /* rg is up to date */
 #define GFS2_RDF_ERROR		0x40000000 /* error in rg */
+#define GFS2_RDF_PREFERRED	0x80000000 /* This rgrp is preferred */
 #define GFS2_RDF_MASK		0xf0000000 /* mask for internal flags */
 	spinlock_t rd_rsspin;           /* protects reservation related vars */
 	struct rb_root rd_rstree;       /* multi-block reservation tree */
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 7474c41..f4e4a0c 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -936,7 +936,7 @@ static int read_rindex_entry(struct gfs2_inode *ip)
 	rgd->rd_gl->gl_vm.start = rgd->rd_addr * bsize;
 	rgd->rd_gl->gl_vm.end = rgd->rd_gl->gl_vm.start + (rgd->rd_length * bsize) - 1;
 	rgd->rd_rgl = (struct gfs2_rgrp_lvb *)rgd->rd_gl->gl_lksb.sb_lvbptr;
-	rgd->rd_flags &= ~GFS2_RDF_UPTODATE;
+	rgd->rd_flags &= ~(GFS2_RDF_UPTODATE | GFS2_RDF_PREFERRED);
 	if (rgd->rd_data > sdp->sd_max_rg_data)
 		sdp->sd_max_rg_data = rgd->rd_data;
 	spin_lock(&sdp->sd_rindex_spin);
@@ -955,6 +955,36 @@ fail:
 }
 
 /**
+ * set_rgrp_preferences - Run all the rgrps, selecting some we prefer to use
+ * @sdp: the GFS2 superblock
+ *
+ * The purpose of this function is to select a subset of the resource groups
+ * and mark them as PREFERRED. We do it in such a way that each node prefers
+ * to use a unique set of rgrps to minimize glock contention.
+ */
+static void set_rgrp_preferences(struct gfs2_sbd *sdp)
+{
+	struct gfs2_rgrpd *rgd, *first;
+	int i;
+
+	/* Skip an initial number of rgrps, based on this node's journal ID.
+	   That should start each node out on its own set. */
+	rgd = gfs2_rgrpd_get_first(sdp);
+	for (i = 0; i < sdp->sd_lockstruct.ls_jid; i++)
+		rgd = gfs2_rgrpd_get_next(rgd);
+	first = rgd;
+
+	do {
+		rgd->rd_flags |= GFS2_RDF_PREFERRED;
+		for (i = 0; i < sdp->sd_journals; i++) {
+			rgd = gfs2_rgrpd_get_next(rgd);
+			if (rgd == first)
+				break;
+		}
+	} while (rgd != first);
+}
+
+/**
  * gfs2_ri_update - Pull in a new resource index from the disk
  * @ip: pointer to the rindex inode
  *
@@ -973,6 +1003,8 @@ static int gfs2_ri_update(struct gfs2_inode *ip)
 	if (error < 0)
 		return error;
 
+	set_rgrp_preferences(sdp);
+
 	sdp->sd_rindex_uptodate = 1;
 	return 0;
 }
@@ -1891,6 +1923,25 @@ static bool gfs2_select_rgrp(struct gfs2_rgrpd **pos, const struct gfs2_rgrpd *b
 }
 
 /**
+ * fast_to_acquire - determine if a resource group will be fast to acquire
+ *
+ * If this is one of our preferred rgrps, it should be quicker to acquire,
+ * because we tried to set ourselves up as dlm lock master.
+ */
+static inline int fast_to_acquire(struct gfs2_rgrpd *rgd)
+{
+	struct gfs2_glock *gl = rgd->rd_gl;
+
+	if (gl->gl_state != LM_ST_UNLOCKED && list_empty(&gl->gl_holders) &&
+	    !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) &&
+	    !test_bit(GLF_DEMOTE, &gl->gl_flags))
+		return 1;
+	if (rgd->rd_flags & GFS2_RDF_PREFERRED)
+		return 1;
+	return 0;
+}
+
+/**
  * gfs2_inplace_reserve - Reserve space in the filesystem
  * @ip: the inode to reserve space for
  * @ap: the allocation parameters
@@ -1932,10 +1983,15 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
 			rg_locked = 0;
 			if (skip && skip--)
 				goto next_rgrp;
-			if (!gfs2_rs_active(rs) && (loops < 2) &&
-			     gfs2_rgrp_used_recently(rs, 1000) &&
-			     gfs2_rgrp_congested(rs->rs_rbm.rgd, loops))
-				goto next_rgrp;
+			if (!gfs2_rs_active(rs)) {
+				if (loops == 0 &&
+				    !fast_to_acquire(rs->rs_rbm.rgd))
+					goto next_rgrp;
+				if ((loops < 2) &&
+				    gfs2_rgrp_used_recently(rs, 1000) &&
+				    gfs2_rgrp_congested(rs->rs_rbm.rgd, loops))
+					goto next_rgrp;
+			}
 			error = gfs2_glock_nq_init(rs->rs_rbm.rgd->rd_gl,
 						   LM_ST_EXCLUSIVE, flags,
 						   &rs->rs_rgd_gh);
-- 
1.8.3.1