Task the logwatcher thread with updating the gauges

They also get updated during resurrection when the checkpoint
logs are output.

Implements #6

src/fellow_log.c

@@ -602,6 +602,30 @@ struct fellow_fd {
 	unsigned			open_cbs_n;
 };
 
+void
+fellow_fd_update_space_stats(struct fellow_fd *ffd)
+{
+	buddy_t *buddy;
+	size_t sz;
+
+	CHECK_OBJ_NOTNULL(ffd, FELLOW_FD_MAGIC);
+	if (ffd->stats == NULL)
+		return;
+
+	/* we get the exact values (which implies lock acquisition)
+	 * because this function is only to be called infrequently
+	 */
+	buddy = ffd->dskbuddy;
+	sz = buddy_space(buddy, 1);
+	ffd->stats->g_dsk_space = sz;
+	ffd->stats->g_dsk_bytes = buddy_size(buddy) - sz;
+
+	buddy = ffd->membuddy;
+	sz = buddy_space(buddy, 1);
+	ffd->stats->g_mem_space = sz;
+	ffd->stats->g_mem_bytes = buddy_size(buddy) - sz;
+}
+
 static void
 fellow_fd_ioctx_get(struct fellow_fd *ffd, struct fellow_fd_ioctx_lease *fdil)
 {
@@ -5373,6 +5397,7 @@ fellow_logwatcher_thread(void *priv)
 	AZ(pthread_mutex_lock(&ffd->logmtx));
 	fellow_logwatcher_new_log_alloc(ffd, new_log_req, &new_log_fdr);
 	while (ffd->watcher_running) {
+		fellow_fd_update_space_stats(ffd);
 		if (ffd->logbuf->ff.inuse) {
 			AZ(pthread_mutex_unlock(&ffd->logmtx));
 			logbuffer_wait_flush_fini(ffd->logbuf);

src/fellow_log_storage.h

@@ -263,3 +263,4 @@ size_t fellow_minsize(void);
 
 typedef void fellow_log_diag_f(const char *fmt, ...);
 void fellow_log_set_diag(struct fellow_fd *ffd, fellow_log_diag_f *diag);
+void fellow_fd_update_space_stats(struct fellow_fd *ffd);

src/fellow_storage.c

@@ -1687,6 +1687,7 @@ sfe_keep(struct sfe_resurrect_priv *sfer)
 		SFE_DIAG(sfer->stvfe->memstv->ident,
 		    "resurrected %u ", sfer->n_resurrected);
 		Pool_Sumstat(sfer->wrk);
+		fellow_fd_update_space_stats(sfer->stvfe->ffd);
 	}
 	return (1);
 }
@@ -2747,30 +2748,12 @@ sfe_panic(struct vsb *vsb, const struct objcore *oc)
 }
 #endif
 
-static void
-sfe_update_space(struct stvfe *stvfe)
-{
-	buddy_t *buddy;
-	size_t sz;
-
-	buddy = fellow_dskbuddy(stvfe->ffd);
-	sz = buddy_space(buddy, 0);
-	stvfe->stats->g_dsk_space = sz;
-	stvfe->stats->g_dsk_bytes = buddy_size(buddy) - sz;
-
-	buddy = stvfe->membuddy;
-	sz = buddy_space(buddy, 0);
-	stvfe->stats->g_mem_space = sz;
-	stvfe->stats->g_mem_bytes = buddy_size(buddy) - sz;
-}
-
 static VCL_BYTES v_matchproto_(stv_var_free_space)
 sfe_free_space(const struct stevedore *stv)
 {
 	struct stvfe *stvfe;
 
 	CAST_OBJ_NOTNULL(stvfe, stv->priv, STVFE_MAGIC);
-	sfe_update_space(stvfe);
 
 	return ((VCL_BYTES)stvfe->stats->g_dsk_space);
 }
@@ -2781,7 +2764,6 @@ sfe_used_space(const struct stevedore *stv)
 	struct stvfe *stvfe;
 
 	CAST_OBJ_NOTNULL(stvfe, stv->priv, STVFE_MAGIC);
-	sfe_update_space(stvfe);
 
 	return ((VCL_BYTES)stvfe->stats->g_dsk_bytes);
 }

src/vmod_slash.man.rst

@@ -812,6 +812,9 @@ observed with VSC clients like :ref:`varnishstat(1)`.
 The counter documentation is available through :ref:`varnishstat(1)`
 and the :ref:`slash-counters(7)` man page.
 
+The ``g_dsk_*`` and ``g_mem_*`` gauges are updated at regular
+intervals of *logbuffer_flush_interval*.
+
 FELLOW DIAGNOSTICS
 ==================
 

src/vmod_slash.vcc

@@ -733,6 +733,9 @@ observed with VSC clients like :ref:`varnishstat(1)`.
 The counter documentation is available through :ref:`varnishstat(1)`
 and the :ref:`slash-counters(7)` man page.
 
+The ``g_dsk_*`` and ``g_mem_*`` gauges are updated at regular
+intervals of *logbuffer_flush_interval*.
+
 FELLOW DIAGNOSTICS
 ==================