Author: jhb
Date: Thu Dec 1 18:46:28 2011
New Revision: 228185
URL: http://svn.freebsd.org/changeset/base/228185
Log:
Enhance the sequential access heuristic used to perform readahead in the
NFS server and reuse it for writes as well to allow writes to the backing
store to be clustered.
- Use a prime number for the size of the heuristic table (1017 is not
prime).
- Move the logic to locate a heuristic entry from the table and compute
the sequential count out of VOP_READ() and into a separate routine.
- Use the logic from sequential_heuristic() in vfs_vnops.c to update the
seqcount when a sequential access is performed rather than just
increasing seqcount by 1. This lets the clustering count ramp up
faster.
- Allow for some reordering of RPCs and if it is detected leave the current
seqcount as-is rather than dropping back to a seqcount of 1. Also,
when out of order access is encountered, cut seqcount in half rather than
dropping it all the way back to 1 to further aid with reordering.
- Fix the new NFS server to properly update the next offset after a
successful VOP_READ() so that the readahead actually works.
Some of these changes came from an earlier patch by Bjorn Gronwall that was
forwarded to me by bde@.
Discussed with: bde, rmacklem, fs@
Submitted by: Bjorn Gronwall (1, 4)
MFC after: 2 weeks
Modified:
head/sys/fs/nfsserver/nfs_nfsdport.c
head/sys/nfsserver/nfs_serv.c
Modified: head/sys/fs/nfsserver/nfs_nfsdport.c
==============================================================================
--- head/sys/fs/nfsserver/nfs_nfsdport.c Thu Dec 1 15:33:58 2011
(r228184)
+++ head/sys/fs/nfsserver/nfs_nfsdport.c Thu Dec 1 18:46:28 2011
(r228185)
@@ -90,20 +90,78 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, issue_de
SYSCTL_INT(_vfs_nfsd, OID_AUTO, enable_locallocks, CTLFLAG_RW,
&nfsrv_dolocallocks, 0, "Enable nfsd to acquire local locks on files");
-#define NUM_HEURISTIC 1017
+#define MAX_REORDERED_RPC 16
+#define NUM_HEURISTIC 1031
#define NHUSE_INIT 64
#define NHUSE_INC 16
#define NHUSE_MAX 2048
static struct nfsheur {
struct vnode *nh_vp; /* vp to match (unreferenced pointer) */
- off_t nh_nextr; /* next offset for sequential detection */
+ off_t nh_nextoff; /* next offset for sequential detection */
int nh_use; /* use count for selection */
int nh_seqcount; /* heuristic */
} nfsheur[NUM_HEURISTIC];
/*
+ * Heuristic to detect sequential operation.
+ */
+static struct nfsheur *
+nfsrv_sequential_heuristic(struct uio *uio, struct vnode *vp)
+{
+ struct nfsheur *nh;
+ int hi, try;
+
+ /* Locate best candidate. */
+ try = 32;
+ hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
+ nh = &nfsheur[hi];
+ while (try--) {
+ if (nfsheur[hi].nh_vp == vp) {
+ nh = &nfsheur[hi];
+ break;
+ }
+ if (nfsheur[hi].nh_use > 0)
+ --nfsheur[hi].nh_use;
+ hi = (hi + 1) % NUM_HEURISTIC;
+ if (nfsheur[hi].nh_use < nh->nh_use)
+ nh = &nfsheur[hi];
+ }
+
+ /* Initialize hint if this is a new file. */
+ if (nh->nh_vp != vp) {
+ nh->nh_vp = vp;
+ nh->nh_nextoff = uio->uio_offset;
+ nh->nh_use = NHUSE_INIT;
+ if (uio->uio_offset == 0)
+ nh->nh_seqcount = 4;
+ else
+ nh->nh_seqcount = 1;
+ }
+
+ /* Calculate heuristic. */
+ if ((uio->uio_offset == 0 && nh->nh_seqcount > 0) ||
+ uio->uio_offset == nh->nh_nextoff) {
+ /* See comments in vfs_vnops.c:sequential_heuristic(). */
+ nh->nh_seqcount += howmany(uio->uio_resid, 16384);
+ if (nh->nh_seqcount > IO_SEQMAX)
+ nh->nh_seqcount = IO_SEQMAX;
+ } else if (qabs(uio->uio_offset - nh->nh_nextoff) <= MAX_REORDERED_RPC *
+ imax(vp->v_mount->mnt_stat.f_iosize, uio->uio_resid)) {
+ /* Probably a reordered RPC, leave seqcount alone. */
+ } else if (nh->nh_seqcount > 1) {
+ nh->nh_seqcount /= 2;
+ } else {
+ nh->nh_seqcount = 0;
+ }
+ nh->nh_use += NHUSE_INC;
+ if (nh->nh_use > NHUSE_MAX)
+ nh->nh_use = NHUSE_MAX;
+ return (nh);
+}
+
+/*
* Get attributes into nfsvattr structure.
*/
int
@@ -567,60 +625,11 @@ nfsvno_read(struct vnode *vp, off_t off,
int i;
struct iovec *iv;
struct iovec *iv2;
- int error = 0, len, left, siz, tlen, ioflag = 0, hi, try = 32;
+ int error = 0, len, left, siz, tlen, ioflag = 0;
struct mbuf *m2 = NULL, *m3;
struct uio io, *uiop = &io;
struct nfsheur *nh;
- /*
- * Calculate seqcount for heuristic
- */
- /*
- * Locate best candidate
- */
-
- hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
- nh = &nfsheur[hi];
-
- while (try--) {
- if (nfsheur[hi].nh_vp == vp) {
- nh = &nfsheur[hi];
- break;
- }
- if (nfsheur[hi].nh_use > 0)
- --nfsheur[hi].nh_use;
- hi = (hi + 1) % NUM_HEURISTIC;
- if (nfsheur[hi].nh_use < nh->nh_use)
- nh = &nfsheur[hi];
- }
-
- if (nh->nh_vp != vp) {
- nh->nh_vp = vp;
- nh->nh_nextr = off;
- nh->nh_use = NHUSE_INIT;
- if (off == 0)
- nh->nh_seqcount = 4;
- else
- nh->nh_seqcount = 1;
- }
-
- /*
- * Calculate heuristic
- */
-
- if ((off == 0 && nh->nh_seqcount > 0) || off == nh->nh_nextr) {
- if (++nh->nh_seqcount > IO_SEQMAX)
- nh->nh_seqcount = IO_SEQMAX;
- } else if (nh->nh_seqcount > 1) {
- nh->nh_seqcount = 1;
- } else {
- nh->nh_seqcount = 0;
- }
- nh->nh_use += NHUSE_INC;
- if (nh->nh_use > NHUSE_MAX)
- nh->nh_use = NHUSE_MAX;
- ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
-
len = left = NFSM_RNDUP(cnt);
m3 = NULL;
/*
@@ -665,6 +674,8 @@ nfsvno_read(struct vnode *vp, off_t off,
uiop->uio_resid = len;
uiop->uio_rw = UIO_READ;
uiop->uio_segflg = UIO_SYSSPACE;
+ nh = nfsrv_sequential_heuristic(uiop, vp);
+ ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
error = VOP_READ(vp, uiop, IO_NODELOCKED | ioflag, cred);
FREE((caddr_t)iv2, M_TEMP);
if (error) {
@@ -672,6 +683,7 @@ nfsvno_read(struct vnode *vp, off_t off,
*mpp = NULL;
goto out;
}
+ nh->nh_nextoff = uiop->uio_offset;
tlen = len - uiop->uio_resid;
cnt = cnt < tlen ? cnt : tlen;
tlen = NFSM_RNDUP(cnt);
@@ -700,6 +712,7 @@ nfsvno_write(struct vnode *vp, off_t off
struct iovec *iv;
int ioflags, error;
struct uio io, *uiop = &io;
+ struct nfsheur *nh;
MALLOC(ivp, struct iovec *, cnt * sizeof (struct iovec), M_TEMP,
M_WAITOK);
@@ -733,7 +746,11 @@ nfsvno_write(struct vnode *vp, off_t off
uiop->uio_segflg = UIO_SYSSPACE;
NFSUIOPROC(uiop, p);
uiop->uio_offset = off;
+ nh = nfsrv_sequential_heuristic(uiop, vp);
+ ioflags |= nh->nh_seqcount << IO_SEQSHIFT;
error = VOP_WRITE(vp, uiop, ioflags, cred);
+ if (error == 0)
+ nh->nh_nextoff = uiop->uio_offset;
FREE((caddr_t)iv, M_TEMP);
NFSEXITCODE(error);
Modified: head/sys/nfsserver/nfs_serv.c
==============================================================================
--- head/sys/nfsserver/nfs_serv.c Thu Dec 1 15:33:58 2011
(r228184)
+++ head/sys/nfsserver/nfs_serv.c Thu Dec 1 18:46:28 2011
(r228185)
@@ -107,14 +107,15 @@ FEATURE(nfsserver, "NFS server");
#define MAX_COMMIT_COUNT (1024 * 1024)
-#define NUM_HEURISTIC 1017
+#define MAX_REORDERED_RPC 16
+#define NUM_HEURISTIC 1031
#define NHUSE_INIT 64
#define NHUSE_INC 16
#define NHUSE_MAX 2048
static struct nfsheur {
struct vnode *nh_vp; /* vp to match (unreferenced pointer) */
- off_t nh_nextr; /* next offset for sequential detection */
+ off_t nh_nextoff; /* next offset for sequential detection */
int nh_use; /* use count for selection */
int nh_seqcount; /* heuristic */
} nfsheur[NUM_HEURISTIC];
@@ -187,6 +188,63 @@ nfsrv_lockedpair_nd(int vfs1, struct nam
}
/*
+ * Heuristic to detect sequential operation.
+ */
+static struct nfsheur *
+nfsrv_sequential_heuristic(struct uio *uio, struct vnode *vp)
+{
+ struct nfsheur *nh;
+ int hi, try;
+
+ /* Locate best candidate. */
+ try = 32;
+ hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
+ nh = &nfsheur[hi];
+ while (try--) {
+ if (nfsheur[hi].nh_vp == vp) {
+ nh = &nfsheur[hi];
+ break;
+ }
+ if (nfsheur[hi].nh_use > 0)
+ --nfsheur[hi].nh_use;
+ hi = (hi + 1) % NUM_HEURISTIC;
+ if (nfsheur[hi].nh_use < nh->nh_use)
+ nh = &nfsheur[hi];
+ }
+
+ /* Initialize hint if this is a new file. */
+ if (nh->nh_vp != vp) {
+ nh->nh_vp = vp;
+ nh->nh_nextoff = uio->uio_offset;
+ nh->nh_use = NHUSE_INIT;
+ if (uio->uio_offset == 0)
+ nh->nh_seqcount = 4;
+ else
+ nh->nh_seqcount = 1;
+ }
+
+ /* Calculate heuristic. */
+ if ((uio->uio_offset == 0 && nh->nh_seqcount > 0) ||
+ uio->uio_offset == nh->nh_nextoff) {
+ /* See comments in vfs_vnops.c:sequential_heuristic(). */
+ nh->nh_seqcount += howmany(uio->uio_resid, 16384);
+ if (nh->nh_seqcount > IO_SEQMAX)
+ nh->nh_seqcount = IO_SEQMAX;
+ } else if (qabs(uio->uio_offset - nh->nh_nextoff) <= MAX_REORDERED_RPC *
+ imax(vp->v_mount->mnt_stat.f_iosize, uio->uio_resid)) {
+ /* Probably a reordered RPC, leave seqcount alone. */
+ } else if (nh->nh_seqcount > 1) {
+ nh->nh_seqcount /= 2;
+ } else {
+ nh->nh_seqcount = 0;
+ }
+ nh->nh_use += NHUSE_INC;
+ if (nh->nh_use > NHUSE_MAX)
+ nh->nh_use = NHUSE_MAX;
+ return (nh);
+}
+
+/*
* nfs v3 access service
*/
int
@@ -843,7 +901,6 @@ nfsrv_read(struct nfsrv_descript *nfsd,
/*
* Calculate byte count to read
*/
-
if (off >= vap->va_size)
cnt = 0;
else if ((off + reqlen) > vap->va_size)
@@ -851,61 +908,6 @@ nfsrv_read(struct nfsrv_descript *nfsd,
else
cnt = reqlen;
- /*
- * Calculate seqcount for heuristic
- */
-
- {
- int hi;
- int try = 32;
-
- /*
- * Locate best candidate
- */
-
- hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) %
NUM_HEURISTIC;
- nh = &nfsheur[hi];
-
- while (try--) {
- if (nfsheur[hi].nh_vp == vp) {
- nh = &nfsheur[hi];
- break;
- }
- if (nfsheur[hi].nh_use > 0)
- --nfsheur[hi].nh_use;
- hi = (hi + 1) % NUM_HEURISTIC;
- if (nfsheur[hi].nh_use < nh->nh_use)
- nh = &nfsheur[hi];
- }
-
- if (nh->nh_vp != vp) {
- nh->nh_vp = vp;
- nh->nh_nextr = off;
- nh->nh_use = NHUSE_INIT;
- if (off == 0)
- nh->nh_seqcount = 4;
- else
- nh->nh_seqcount = 1;
- }
-
- /*
- * Calculate heuristic
- */
-
- if ((off == 0 && nh->nh_seqcount > 0) || off == nh->nh_nextr) {
- if (++nh->nh_seqcount > IO_SEQMAX)
- nh->nh_seqcount = IO_SEQMAX;
- } else if (nh->nh_seqcount > 1) {
- nh->nh_seqcount = 1;
- } else {
- nh->nh_seqcount = 0;
- }
- nh->nh_use += NHUSE_INC;
- if (nh->nh_use > NHUSE_MAX)
- nh->nh_use = NHUSE_MAX;
- ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
- }
-
nfsm_reply(NFSX_POSTOPORFATTR(v3) + 3 * NFSX_UNSIGNED+nfsm_rndup(cnt));
if (v3) {
tl = nfsm_build(u_int32_t *, NFSX_V3FATTR + 4 * NFSX_UNSIGNED);
@@ -963,9 +965,11 @@ nfsrv_read(struct nfsrv_descript *nfsd,
uiop->uio_resid = len;
uiop->uio_rw = UIO_READ;
uiop->uio_segflg = UIO_SYSSPACE;
+ nh = nfsrv_sequential_heuristic(uiop, vp);
+ ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
error = VOP_READ(vp, uiop, IO_NODELOCKED | ioflag, cred);
- off = uiop->uio_offset;
- nh->nh_nextr = off;
+ if (error == 0)
+ nh->nh_nextoff = uiop->uio_offset;
free((caddr_t)iv2, M_TEMP);
if (error || (getret = VOP_GETATTR(vp, vap, cred))) {
if (!error)
@@ -1030,6 +1034,7 @@ nfsrv_write(struct nfsrv_descript *nfsd,
int v3 = (nfsd->nd_flag & ND_NFSV3);
struct mbuf *mb, *mreq;
struct vnode *vp = NULL;
+ struct nfsheur *nh;
nfsfh_t nfh;
fhandle_t *fhp;
struct uio io, *uiop = &io;
@@ -1170,7 +1175,11 @@ nfsrv_write(struct nfsrv_descript *nfsd,
uiop->uio_segflg = UIO_SYSSPACE;
uiop->uio_td = NULL;
uiop->uio_offset = off;
+ nh = nfsrv_sequential_heuristic(uiop, vp);
+ ioflags |= nh->nh_seqcount << IO_SEQSHIFT;
error = VOP_WRITE(vp, uiop, ioflags, cred);
+ if (error == 0)
+ nh->nh_nextoff = uiop->uio_offset;
/* Unlocked write. */
nfsrvstats.srvvop_writes++;
free((caddr_t)iv, M_TEMP);
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