MFC Alexander Motin's GEOM direct dispatch work:

r256603:
Introduce new function devstat_end_transaction_bio_bt(), adding new argument
to specify present time.  Use this function to move binuptime() out of lock,
substantially reducing lock congestion when slow timecounter is used.

r256606:
Move g_io_deliver() out of the lock, as required for direct dispatch.
Move g_destroy_bio() out too to reduce lock scope even more.

r256607:
Fix passing uninitialized bio_resid argument to g_trace().

r256610:
Add unmapped I/O support to GEOM RAID.

r256830:
Restore BIO_UNMAPPED and BIO_TRANSIENT_MAPPING in biodonne() when unmapping
temporary mapped buffer.  That fixes double unmap if biodone() called twice
for the same BIO (but with different done methods).

r256880:
Merge GEOM direct dispatch changes from the projects/camlock branch.

When safety requirements are met, it allows to avoid passing I/O requests
to GEOM g_up/g_down thread, executing them directly in the caller context.
That allows to avoid CPU bottlenecks in g_up/g_down threads, plus avoid
several context switches per I/O.

r259247:
Fix bug introduced at r256607.  We have to recalculate bp_resid here since
sizes of original and completed requests may differ due to end of media.

Testing of the stable/10 merge was done by Netflix, but all of the credit
goes to Alexander and iX Systems.

Submitted by:   mav
Sponsored by:   iX Systems

2 files changed, 12 insertions, 2 deletions

diff --git a/sys/geom/nop/g_nop.c b/sys/geom/nop/g_nop.c
index a1a1ad1..bd72d78 100644
--- a/sys/geom/nop/g_nop.c
+++ b/sys/geom/nop/g_nop.c
@@ -107,6 +107,7 @@ g_nop_start(struct bio *bp)
 	gp = bp->bio_to->geom;
 	sc = gp->softc;
 	G_NOP_LOGREQ(bp, "Request received.");
+	mtx_lock(&sc->sc_lock);
 	switch (bp->bio_cmd) {
 	case BIO_READ:
 		sc->sc_reads++;
@@ -119,6 +120,7 @@ g_nop_start(struct bio *bp)
 		failprob = sc->sc_wfailprob;
 		break;
 	}
+	mtx_unlock(&sc->sc_lock);
 	if (failprob > 0) {
 		u_int rval;
 
@@ -224,6 +226,7 @@ g_nop_create(struct gctl_req *req, struct g_class *mp, struct g_provider *pp,
 	sc->sc_writes = 0;
 	sc->sc_readbytes = 0;
 	sc->sc_wrotebytes = 0;
+	mtx_init(&sc->sc_lock, "gnop lock", NULL, MTX_DEF);
 	gp->softc = sc;
 	gp->start = g_nop_start;
 	gp->orphan = g_nop_orphan;
@@ -232,10 +235,12 @@ g_nop_create(struct gctl_req *req, struct g_class *mp, struct g_provider *pp,
 	gp->dumpconf = g_nop_dumpconf;
 
 	newpp = g_new_providerf(gp, "%s", gp->name);
+	newpp->flags |= G_PF_DIRECT_SEND | G_PF_DIRECT_RECEIVE;
 	newpp->mediasize = size;
 	newpp->sectorsize = secsize;
 
 	cp = g_new_consumer(gp);
+	cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
 	error = g_attach(cp, pp);
 	if (error != 0) {
 		gctl_error(req, "Cannot attach to provider %s.", pp->name);
@@ -251,6 +256,7 @@ fail:
 		g_detach(cp);
 	g_destroy_consumer(cp);
 	g_destroy_provider(newpp);
+	mtx_destroy(&sc->sc_lock);
 	g_free(gp->softc);
 	g_destroy_geom(gp);
 	return (error);
@@ -259,10 +265,12 @@ fail:
 static int
 g_nop_destroy(struct g_geom *gp, boolean_t force)
 {
+	struct g_nop_softc *sc;
 	struct g_provider *pp;
 
 	g_topology_assert();
-	if (gp->softc == NULL)
+	sc = gp->softc;
+	if (sc == NULL)
 		return (ENXIO);
 	pp = LIST_FIRST(&gp->provider);
 	if (pp != NULL && (pp->acr != 0 || pp->acw != 0 || pp->ace != 0)) {
@@ -277,8 +285,9 @@ g_nop_destroy(struct g_geom *gp, boolean_t force)
 	} else {
 		G_NOP_DEBUG(0, "Device %s removed.", gp->name);
 	}
-	g_free(gp->softc);
 	gp->softc = NULL;
+	mtx_destroy(&sc->sc_lock);
+	g_free(sc);
 	g_wither_geom(gp, ENXIO);
 
 	return (0);
diff --git a/sys/geom/nop/g_nop.h b/sys/geom/nop/g_nop.h
index da555ec..3e37c05 100644
--- a/sys/geom/nop/g_nop.h
+++ b/sys/geom/nop/g_nop.h
@@ -65,6 +65,7 @@ struct g_nop_softc {
 	uintmax_t	sc_writes;
 	uintmax_t	sc_readbytes;
 	uintmax_t	sc_wrotebytes;
+	struct mtx	sc_lock;
 };
 #endif	/* _KERNEL */