MFC r321794: Improve FHA locality control for NFS read/write requests.

This change adds two new tunables, allowing to control serialization for
read and write NFS requests separately.  It does not change the default
behavior since there are too many factors to consider, but gives additional
space for further experiments and tuning.

The main motivation for this change is very low write speed in case of ZFS
with sync=always or when NFS clients requests sychronous operation, when
every separate request has to be written/flushed to ZIL, and requests are
processed one at a time.  Setting vfs.nfsd.fha.write=0 in that case allows
to increase ZIL throughput by several times by coalescing writes and cache
flushes.  There is a worry that doing it may increase data fragmentation
on disks, but I suppose it should not happen for pool with SLOG.

Sponsored by:	iXsystems, Inc.

3 files changed, 35 insertions, 29 deletions

diff --git a/sys/fs/nfsserver/nfs_fha_new.c b/sys/fs/nfsserver/nfs_fha_new.c
index 2e7115f..4c505a4 100644
--- a/sys/fs/nfsserver/nfs_fha_new.c
+++ b/sys/fs/nfsserver/nfs_fha_new.c
@@ -93,7 +93,7 @@ fhanew_init(void *foo)
 	sysctl_ctx_init(&softc->sysctl_ctx);
 	softc->sysctl_tree = SYSCTL_ADD_NODE(&softc->sysctl_ctx,
 	    SYSCTL_STATIC_CHILDREN(_vfs_nfsd), OID_AUTO, "fha", CTLFLAG_RD,
-	    0, "fha node");
+	    0, "NFS File Handle Affinity (FHA)");
 	if (softc->sysctl_tree == NULL) {
 		printf("%s: unable to allocate sysctl tree\n", __func__);
 		return;
diff --git a/sys/nfs/nfs_fha.c b/sys/nfs/nfs_fha.c
index 45e1701..bf54d58 100644
--- a/sys/nfs/nfs_fha.c
+++ b/sys/nfs/nfs_fha.c
@@ -51,7 +51,6 @@ static MALLOC_DEFINE(M_NFS_FHA, "NFS FHA", "NFS FHA");
 void
 fha_init(struct fha_params *softc)
 {
-	char tmpstr[128];
 	int i;
 
 	for (i = 0; i < FHA_HASH_SIZE; i++)
@@ -61,47 +60,38 @@ fha_init(struct fha_params *softc)
 	 * Set the default tuning parameters.
 	 */
 	softc->ctls.enable = FHA_DEF_ENABLE;
+	softc->ctls.read = FHA_DEF_READ;
+	softc->ctls.write = FHA_DEF_WRITE;
 	softc->ctls.bin_shift = FHA_DEF_BIN_SHIFT;
 	softc->ctls.max_nfsds_per_fh = FHA_DEF_MAX_NFSDS_PER_FH;
 	softc->ctls.max_reqs_per_nfsd = FHA_DEF_MAX_REQS_PER_NFSD;
 
 	/*
-	 * Allow the user to override the defaults at boot time with
-	 * tunables.
-	 */
-	snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.enable",
-	    softc->server_name);
-	TUNABLE_INT_FETCH(tmpstr, &softc->ctls.enable);
-	snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.bin_shift",
-	    softc->server_name);
-	TUNABLE_INT_FETCH(tmpstr, &softc->ctls.bin_shift);
-	snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.max_nfsds_per_fh",
-	    softc->server_name);
-	TUNABLE_INT_FETCH(tmpstr, &softc->ctls.max_nfsds_per_fh);
-	snprintf(tmpstr, sizeof(tmpstr), "vfs.%s.fha.max_reqs_per_nfsd",
-	    softc->server_name);
-	TUNABLE_INT_FETCH(tmpstr, &softc->ctls.max_reqs_per_nfsd);
-
-	/*
-	 * Add sysctls so the user can change the tuning parameters at
-	 * runtime.
+	 * Add sysctls so the user can change the tuning parameters.
 	 */
 	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
-	    OID_AUTO, "enable", CTLFLAG_RW,
+	    OID_AUTO, "enable", CTLFLAG_RWTUN,
 	    &softc->ctls.enable, 0, "Enable NFS File Handle Affinity (FHA)");
 
 	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
-	    OID_AUTO, "bin_shift", CTLFLAG_RW,
-	    &softc->ctls.bin_shift, 0, "For FHA reads, no two requests will "
-	    "contend if they're 2^(bin_shift) bytes apart");
+	    OID_AUTO, "read", CTLFLAG_RWTUN,
+	    &softc->ctls.read, 0, "Enable NFS FHA read locality");
+
+	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
+	    OID_AUTO, "write", CTLFLAG_RWTUN,
+	    &softc->ctls.write, 0, "Enable NFS FHA write locality");
 
 	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
-	    OID_AUTO, "max_nfsds_per_fh", CTLFLAG_RW,
+	    OID_AUTO, "bin_shift", CTLFLAG_RWTUN,
+	    &softc->ctls.bin_shift, 0, "Maximum locality distance 2^(bin_shift) bytes");
+
+	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
+	    OID_AUTO, "max_nfsds_per_fh", CTLFLAG_RWTUN,
 	    &softc->ctls.max_nfsds_per_fh, 0, "Maximum nfsd threads that "
 	    "should be working on requests for the same file handle");
 
 	SYSCTL_ADD_UINT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
-	    OID_AUTO, "max_reqs_per_nfsd", CTLFLAG_RW,
+	    OID_AUTO, "max_reqs_per_nfsd", CTLFLAG_RWTUN,
 	    &softc->ctls.max_reqs_per_nfsd, 0, "Maximum requests that "
 	    "single nfsd thread should be working on at any time");
 
@@ -144,6 +134,7 @@ fha_extract_info(struct svc_req *req, struct fha_info *i,
 	i->fh = ++random_fh;
 	i->offset = 0;
 	i->locktype = LK_EXCLUSIVE;
+	i->read = i->write = 0;
 
 	/*
 	 * Extract the procnum and convert to v3 form if necessary,
@@ -169,6 +160,9 @@ fha_extract_info(struct svc_req *req, struct fha_info *i,
 	if (cb->no_offset(procnum))
 		goto out;
 
+	i->read = cb->is_read(procnum);
+	i->write = cb->is_write(procnum);
+
 	error = cb->realign(&req->rq_args, M_NOWAIT);
 	if (error)
 		goto out;
@@ -181,7 +175,7 @@ fha_extract_info(struct svc_req *req, struct fha_info *i,
 		goto out;
 
 	/* Content ourselves with zero offset for all but reads. */
-	if (cb->is_read(procnum) || cb->is_write(procnum))
+	if (i->read || i->write)
 		cb->get_offset(&md, &dpos, v3, i);
 
 out:
@@ -311,8 +305,13 @@ fha_hash_entry_choose_thread(struct fha_params *softc,
 			return (thread);
 		}
 
+		/* Check whether we should consider locality. */
+		if ((i->read && !softc->ctls.read) ||
+		    (i->write && !softc->ctls.write))
+			goto noloc;
+
 		/*
-		 * Check for read locality, making sure that we won't
+		 * Check for locality, making sure that we won't
 		 * exceed our per-thread load limit in the process.
 		 */
 		offset1 = i->offset;
@@ -332,6 +331,7 @@ fha_hash_entry_choose_thread(struct fha_params *softc,
 			}
 		}
 
+noloc:
 		/*
 		 * We don't have a locality match, so skip this thread,
 		 * but keep track of the most attractive thread in case
diff --git a/sys/nfs/nfs_fha.h b/sys/nfs/nfs_fha.h
index 58aa7fe..27dec1b 100644
--- a/sys/nfs/nfs_fha.h
+++ b/sys/nfs/nfs_fha.h
@@ -31,6 +31,8 @@
 
 /* Sysctl defaults. */
 #define FHA_DEF_ENABLE			1
+#define FHA_DEF_READ			1
+#define FHA_DEF_WRITE			1
 #define FHA_DEF_BIN_SHIFT		22 /* 4MB */
 #define FHA_DEF_MAX_NFSDS_PER_FH	8
 #define FHA_DEF_MAX_REQS_PER_NFSD	0  /* Unlimited */
@@ -39,6 +41,8 @@
 
 struct fha_ctls {
 	int	 enable;
+	int	 read;
+	int	 write;
 	uint32_t bin_shift;
 	uint32_t max_nfsds_per_fh;
 	uint32_t max_reqs_per_nfsd;
@@ -79,6 +83,8 @@ struct fha_info {
 	u_int64_t fh;
 	off_t offset;
 	int locktype;
+	int read;
+	int write;
 };
 
 struct fha_callbacks {