[6.0] d801eb11d Introduce '-' records in VSM _.index files, to reduce VFS workload.

[Martin Blix Grydeland]

commit d801eb11d033154c8c483c12b1bfd7af2ef64ede
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Thu Aug 1 08:00:56 2019 +0000

    Introduce '-' records in VSM _.index files, to reduce VFS workload.

diff --git a/bin/varnishd/common/common_vsmw.c b/bin/varnishd/common/common_vsmw.c
index c865fb233..3fa89c1ce 100644
--- a/bin/varnishd/common/common_vsmw.c
+++ b/bin/varnishd/common/common_vsmw.c
@@ -113,6 +113,8 @@ struct vsmw {
 	struct vsb			*vsb;
 	pid_t				pid;
 	time_t				birth;
+	uint64_t			nsegs;
+	uint64_t			nsubs;
 };
 
 /*--------------------------------------------------------------------*/
@@ -127,12 +129,14 @@ vsmw_idx_head(const struct vsmw *vsmw, int fd)
 }
 
 static void
-vsmw_fmt_index(const struct vsmw *vsmw, const struct vsmwseg *seg)
+vsmw_fmt_index(const struct vsmw *vsmw, const struct vsmwseg *seg, char act)
 {
 
 	CHECK_OBJ_NOTNULL(vsmw, VSMW_MAGIC);
 	CHECK_OBJ_NOTNULL(seg, VSMWSEG_MAGIC);
-	VSB_printf(vsmw->vsb, "+ %s %zu %zu %s %s\n",
+	AN(seg->cluster);
+	VSB_printf(vsmw->vsb, "%c %s %zu %zu %s %s\n",
+	    act,
 	    seg->cluster->fn,
 	    seg->off,
 	    seg->len,
@@ -166,20 +170,33 @@ vsmw_mkent(const struct vsmw *vsmw, const char *pfx)
 /*--------------------------------------------------------------------*/
 
 static void
-vsmw_addseg(struct vsmw *vsmw, struct vsmwseg *seg)
+vsmw_append_record(struct vsmw *vsmw, struct vsmwseg *seg, char act)
 {
 	int fd;
 	ssize_t s;
 
-	VTAILQ_INSERT_TAIL(&vsmw->segs, seg, list);
+	CHECK_OBJ_NOTNULL(vsmw, VSMW_MAGIC);
+	CHECK_OBJ_NOTNULL(seg, VSMWSEG_MAGIC);
 	fd = openat(vsmw->vdirfd, vsmw->idx, O_APPEND | O_WRONLY);
 	assert(fd >= 0);
 	VSB_clear(vsmw->vsb);
-	vsmw_fmt_index(vsmw, seg);
+	vsmw_fmt_index(vsmw, seg, act);
 	AZ(VSB_finish(vsmw->vsb));
 	s = write(fd, VSB_data(vsmw->vsb), VSB_len(vsmw->vsb));
-	assert(s == VSB_len(vsmw->vsb));
+	assert(s == VSB_len(vsmw->vsb)); // XXX handle ENOSPC? #2764
 	AZ(close(fd));
+	vsmw->nsegs++;
+}
+
+/*--------------------------------------------------------------------*/
+
+static void
+vsmw_addseg(struct vsmw *vsmw, struct vsmwseg *seg)
+{
+
+	VTAILQ_INSERT_TAIL(&vsmw->segs, seg, list);
+	vsmw_append_record(vsmw, seg, '+');
+	vsmw->nsegs++;
 }
 
 /*--------------------------------------------------------------------*/
@@ -190,16 +207,19 @@ vsmw_delseg(struct vsmw *vsmw, struct vsmwseg *seg, int fixidx)
 	char *t = NULL;
 	ssize_t s;
 	int fd;
+	struct vsmwseg *s2;
 
 	CHECK_OBJ_NOTNULL(vsmw, VSMW_MAGIC);
 	CHECK_OBJ_NOTNULL(seg, VSMWSEG_MAGIC);
 
 	VTAILQ_REMOVE(&vsmw->segs, seg, list);
-	REPLACE(seg->class, NULL);
-	REPLACE(seg->id, NULL);
-	FREE_OBJ(seg);
 
-	if (fixidx) {
+	vsmw->nsegs--;
+	if (vsmw->nsubs < vsmw->nsegs || !fixidx) {
+		vsmw_append_record(vsmw, seg, '-');
+		vsmw->nsubs++;
+	} else {
+		vsmw->nsubs = 0;
 		vsmw_mkent(vsmw, vsmw->idx);
 		REPLACE(t, VSB_data(vsmw->vsb));
 		AN(t);
@@ -208,8 +228,8 @@ vsmw_delseg(struct vsmw *vsmw, struct vsmwseg *seg, int fixidx)
 		assert(fd >= 0);
 		vsmw_idx_head(vsmw, fd);
 		VSB_clear(vsmw->vsb);
-		VTAILQ_FOREACH(seg, &vsmw->segs, list)
-			vsmw_fmt_index(vsmw, seg);
+		VTAILQ_FOREACH(s2, &vsmw->segs, list)
+			vsmw_fmt_index(vsmw, s2, '+');
 		AZ(VSB_finish(vsmw->vsb));
 		s = write(fd, VSB_data(vsmw->vsb), VSB_len(vsmw->vsb));
 		assert(s == VSB_len(vsmw->vsb));
@@ -217,6 +237,9 @@ vsmw_delseg(struct vsmw *vsmw, struct vsmwseg *seg, int fixidx)
 		AZ(renameat(vsmw->vdirfd, t, vsmw->vdirfd, vsmw->idx));
 		REPLACE(t, NULL);
 	}
+	REPLACE(seg->class, NULL);
+	REPLACE(seg->id, NULL);
+	FREE_OBJ(seg);
 }
 
 /*--------------------------------------------------------------------*/
diff --git a/lib/libvarnishapi/vsm.c b/lib/libvarnishapi/vsm.c
index 1e200e75f..43f3394d8 100644
--- a/lib/libvarnishapi/vsm.c
+++ b/lib/libvarnishapi/vsm.c
@@ -463,7 +463,7 @@ vsm_vlu_plus(struct vsm *vd, struct vsm_set *vs, const char *line)
 
 	if (av[0] != NULL || ac < 4 || ac > 6) {
 		(void)(vsm_diag(vd,
-		    "vsm_refresh_set2: bad index (%d/%s)",
+		    "vsm_vlu_plus: bad index (%d/%s)",
 		    ac, av[0]));
 		VAV_Free(av);
 		return(-1);
@@ -496,6 +496,39 @@ vsm_vlu_plus(struct vsm *vd, struct vsm_set *vs, const char *line)
 	return (0);
 }
 
+static int
+vsm_vlu_minus(struct vsm *vd, struct vsm_set *vs, const char *line)
+{
+	char **av;
+	int ac;
+	struct vsm_seg *vg, *vg2;
+
+	av = VAV_Parse(line + 1, &ac, 0);
+
+	if (av[0] != NULL || ac < 4 || ac > 6) {
+		(void)(vsm_diag(vd,
+		    "vsm_vlu_minus: bad index (%d/%s)",
+		    ac, av[0]));
+		VAV_Free(av);
+		return(-1);
+	}
+
+	VTAILQ_FOREACH_SAFE(vg, &vs->segs, list, vg2) {
+		if (vsm_cmp_av(&vg->av[1], &av[1]))
+			continue;
+		VTAILQ_REMOVE(&vs->segs, vg, list);
+		if (vg->refs) {
+			vg->flags |= VSM_FLAG_STALE;
+			VTAILQ_INSERT_TAIL(&vs->stale, vg, list);
+		} else {
+			VAV_Free(vg->av);
+			FREE_OBJ(vg);
+		}
+		break;
+	}
+	return (0);
+}
+
 static int v_matchproto_(vlu_f)
 vsm_vlu_func(void *priv, const char *line)
 {
@@ -519,6 +552,9 @@ vsm_vlu_func(void *priv, const char *line)
 	case '+':
 		i = vsm_vlu_plus(vd, vs, line);
 		break;
+	case '-':
+		i = vsm_vlu_minus(vd, vs, line);
+		break;
 	default:
 		break;
 	}