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diff --git a/sys/geom/geom_vfs.c b/sys/geom/geom_vfs.c
--- a/sys/geom/geom_vfs.c
+++ b/sys/geom/geom_vfs.c
@@ -36,10 +36,12 @@
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sbuf.h>
+#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <geom/geom.h>
+#include <geom/geom_disk.h>
#include <geom/geom_vfs.h>
/*
@@ -57,8 +59,30 @@
bool sc_orphaned;
int sc_enxio_active;
int sc_enxio_reported;
+ long sc_async_writes;
+ long sc_async_write_limit;
};
+SYSCTL_DECL(_kern_geom);
+
+static long g_vfs_hdd_async_limit = 8;
+SYSCTL_LONG(_kern_geom, OID_AUTO, hdd_async_limit, CTLFLAG_RWTUN,
+ &g_vfs_hdd_async_limit, 0,
+ "Number of async I/Os allowed concurrently per top-level geom consumer on HDD.");
+
+static long g_vfs_ssd_async_limit = 8;
+SYSCTL_LONG(_kern_geom, OID_AUTO, ssd_async_limit, CTLFLAG_RWTUN,
+ &g_vfs_ssd_async_limit, 0,
+ "Number of async I/Os allowed concurrently per top-level geom consumer on SSD.");
+
+static long g_vfs_writes_throttled = 0;
+SYSCTL_LONG(_kern_geom, OID_AUTO, writes_throttled, CTLFLAG_RD,
+ &g_vfs_writes_throttled, 0,
+ "Number of async I/Os converted to sync.");
+
+static void g_vfs_wait_wakeup(bool *);
+static void g_vfs_wait_block(bool *);
+
static struct buf_ops __g_vfs_bufops = {
.bop_name = "GEOM_VFS",
.bop_write = bufwrite,
@@ -166,9 +190,10 @@
else
bp->b_error = bip->bio_error;
bp->b_resid = bp->b_bcount - bip->bio_completed;
- g_destroy_bio(bip);
mtx_lock(&sc->sc_mtx);
+ if (bp->b_iocmd == BIO_WRITE && (bp->b_flags & B_ASYNC) != 0)
+ sc->sc_async_writes--;
destroy = ((--sc->sc_active) == 0 && sc->sc_orphaned);
if (destroy) {
event = sc->sc_event;
@@ -176,18 +201,54 @@
} else
event = NULL;
mtx_unlock(&sc->sc_mtx);
+
+ if (bip->bio_caller1 != NULL)
+ g_vfs_wait_wakeup(bip->bio_caller1);
+ g_destroy_bio(bip);
+
if (destroy)
g_post_event_ep(g_vfs_destroy, cp, event, NULL);
bufdone(bp);
}
+/*
+ * Rendezvous used to throttle async writes in g_vfs_strategy(): a bool on the
+ * throttled thread's own stack, used as a wait channel, to avoid racing bp
+ * destruction. g_vfs_wait_block can't timeout w/o creating a hazard.
+ */
+static void
+g_vfs_wait_wakeup(bool *donep)
+{
+ struct mtx *mtxp;
+
+ mtxp = mtx_pool_find(mtxpool_sleep, donep);
+ mtx_lock(mtxp);
+ *donep = true;
+ wakeup(donep);
+ mtx_unlock(mtxp);
+}
+
+static void
+g_vfs_wait_block(bool *donep)
+{
+ struct mtx *mtxp;
+
+ mtxp = mtx_pool_find(mtxpool_sleep, donep);
+ mtx_lock(mtxp);
+ while (!*donep)
+ msleep(donep, mtxp, PRIBIO, "gvfsrun", 0);
+ mtx_unlock(mtxp);
+}
+
void
g_vfs_strategy(struct bufobj *bo, struct buf *bp)
{
struct g_vfs_softc *sc;
struct g_consumer *cp;
struct bio *bip;
+ bool done;
+ bool throttle;
cp = bo->bo_private;
sc = cp->geom->softc;
@@ -206,6 +267,11 @@
return;
}
sc->sc_active++;
+ throttle = false;
+ if (bp->b_iocmd == BIO_WRITE && (bp->b_flags & B_ASYNC) != 0) {
+ sc->sc_async_writes++;
+ throttle = sc->sc_async_writes > sc->sc_async_write_limit;
+ }
mtx_unlock(&sc->sc_mtx);
bip = g_alloc_bio();
@@ -221,11 +287,20 @@
bip->bio_flags |= bp->b_ioflags;
bip->bio_done = g_vfs_done;
bip->bio_caller2 = bp;
+ if (throttle) {
+ done = false;
+ bip->bio_caller1 = &done;
+ g_vfs_writes_throttled++;
+ } else {
+ bip->bio_caller1 = NULL;
+ }
#if defined(BUF_TRACKING) || defined(FULL_BUF_TRACKING)
buf_track(bp, __func__);
bip->bio_track_bp = bp;
#endif
g_io_request(bip, cp);
+ if (throttle)
+ g_vfs_wait_block(&done);
}
static void
@@ -271,6 +346,8 @@
struct g_consumer *cp;
struct g_vfs_softc *sc;
struct bufobj *bo;
+ uint16_t rate;
+ long async_limit;
int error;
g_topology_assert();
@@ -308,6 +385,16 @@
g_wither_geom(gp, ENXIO);
return (ENXIO);
}
+ /*
+ * Throttle based on SSD vs HDD, assume anything that's
+ * not non-rotating is a HDD.
+ */
+ if (g_getattr("GEOM::rotation_rate", cp, &rate) == 0 &&
+ rate == DISK_RR_NON_ROTATING)
+ async_limit = g_vfs_hdd_async_limit;
+ else
+ async_limit = g_vfs_ssd_async_limit;
+ sc->sc_async_write_limit = async_limit;
vnode_create_disk_vobject(vp, pp->mediasize, curthread);
*cpp = cp;
cp->private = vp;

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