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
This commit is contained in:
John Baldwin
parent
0b6230f135
commit
574862c8ba
@ -90,19 +90,77 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, issue_delegations, CTLFLAG_RW,
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SYSCTL_INT(_vfs_nfsd, OID_AUTO, enable_locallocks, CTLFLAG_RW,
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&nfsrv_dolocallocks, 0, "Enable nfsd to acquire local locks on files");
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#define NUM_HEURISTIC 1017
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#define MAX_REORDERED_RPC 16
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#define NUM_HEURISTIC 1031
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#define NHUSE_INIT 64
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#define NHUSE_INC 16
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#define NHUSE_MAX 2048
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static struct nfsheur {
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struct vnode *nh_vp; /* vp to match (unreferenced pointer) */
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off_t nh_nextr; /* next offset for sequential detection */
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off_t nh_nextoff; /* next offset for sequential detection */
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int nh_use; /* use count for selection */
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int nh_seqcount; /* heuristic */
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} nfsheur[NUM_HEURISTIC];
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/*
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* Heuristic to detect sequential operation.
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*/
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static struct nfsheur *
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nfsrv_sequential_heuristic(struct uio *uio, struct vnode *vp)
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{
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struct nfsheur *nh;
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int hi, try;
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/* Locate best candidate. */
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try = 32;
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hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
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nh = &nfsheur[hi];
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while (try--) {
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if (nfsheur[hi].nh_vp == vp) {
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nh = &nfsheur[hi];
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break;
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}
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if (nfsheur[hi].nh_use > 0)
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--nfsheur[hi].nh_use;
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hi = (hi + 1) % NUM_HEURISTIC;
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if (nfsheur[hi].nh_use < nh->nh_use)
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nh = &nfsheur[hi];
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}
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/* Initialize hint if this is a new file. */
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if (nh->nh_vp != vp) {
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nh->nh_vp = vp;
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nh->nh_nextoff = uio->uio_offset;
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nh->nh_use = NHUSE_INIT;
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if (uio->uio_offset == 0)
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nh->nh_seqcount = 4;
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else
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nh->nh_seqcount = 1;
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}
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/* Calculate heuristic. */
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if ((uio->uio_offset == 0 && nh->nh_seqcount > 0) ||
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uio->uio_offset == nh->nh_nextoff) {
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/* See comments in vfs_vnops.c:sequential_heuristic(). */
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nh->nh_seqcount += howmany(uio->uio_resid, 16384);
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if (nh->nh_seqcount > IO_SEQMAX)
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nh->nh_seqcount = IO_SEQMAX;
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} else if (qabs(uio->uio_offset - nh->nh_nextoff) <= MAX_REORDERED_RPC *
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imax(vp->v_mount->mnt_stat.f_iosize, uio->uio_resid)) {
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/* Probably a reordered RPC, leave seqcount alone. */
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} else if (nh->nh_seqcount > 1) {
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nh->nh_seqcount /= 2;
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} else {
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nh->nh_seqcount = 0;
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}
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nh->nh_use += NHUSE_INC;
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if (nh->nh_use > NHUSE_MAX)
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nh->nh_use = NHUSE_MAX;
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return (nh);
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}
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/*
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* Get attributes into nfsvattr structure.
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*/
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@ -567,60 +625,11 @@ nfsvno_read(struct vnode *vp, off_t off, int cnt, struct ucred *cred,
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int i;
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struct iovec *iv;
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struct iovec *iv2;
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int error = 0, len, left, siz, tlen, ioflag = 0, hi, try = 32;
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int error = 0, len, left, siz, tlen, ioflag = 0;
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struct mbuf *m2 = NULL, *m3;
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struct uio io, *uiop = &io;
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struct nfsheur *nh;
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/*
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* Calculate seqcount for heuristic
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*/
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/*
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* Locate best candidate
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*/
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hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
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nh = &nfsheur[hi];
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while (try--) {
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if (nfsheur[hi].nh_vp == vp) {
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nh = &nfsheur[hi];
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break;
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}
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if (nfsheur[hi].nh_use > 0)
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--nfsheur[hi].nh_use;
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hi = (hi + 1) % NUM_HEURISTIC;
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if (nfsheur[hi].nh_use < nh->nh_use)
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nh = &nfsheur[hi];
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}
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if (nh->nh_vp != vp) {
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nh->nh_vp = vp;
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nh->nh_nextr = off;
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nh->nh_use = NHUSE_INIT;
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if (off == 0)
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nh->nh_seqcount = 4;
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else
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nh->nh_seqcount = 1;
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}
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/*
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* Calculate heuristic
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*/
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if ((off == 0 && nh->nh_seqcount > 0) || off == nh->nh_nextr) {
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if (++nh->nh_seqcount > IO_SEQMAX)
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nh->nh_seqcount = IO_SEQMAX;
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} else if (nh->nh_seqcount > 1) {
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nh->nh_seqcount = 1;
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} else {
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nh->nh_seqcount = 0;
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}
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nh->nh_use += NHUSE_INC;
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if (nh->nh_use > NHUSE_MAX)
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nh->nh_use = NHUSE_MAX;
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ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
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len = left = NFSM_RNDUP(cnt);
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m3 = NULL;
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/*
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@ -665,6 +674,8 @@ nfsvno_read(struct vnode *vp, off_t off, int cnt, struct ucred *cred,
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uiop->uio_resid = len;
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uiop->uio_rw = UIO_READ;
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uiop->uio_segflg = UIO_SYSSPACE;
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nh = nfsrv_sequential_heuristic(uiop, vp);
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ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
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error = VOP_READ(vp, uiop, IO_NODELOCKED | ioflag, cred);
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FREE((caddr_t)iv2, M_TEMP);
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if (error) {
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@ -672,6 +683,7 @@ nfsvno_read(struct vnode *vp, off_t off, int cnt, struct ucred *cred,
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*mpp = NULL;
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goto out;
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}
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nh->nh_nextoff = uiop->uio_offset;
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tlen = len - uiop->uio_resid;
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cnt = cnt < tlen ? cnt : tlen;
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tlen = NFSM_RNDUP(cnt);
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@ -700,6 +712,7 @@ nfsvno_write(struct vnode *vp, off_t off, int retlen, int cnt, int stable,
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struct iovec *iv;
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int ioflags, error;
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struct uio io, *uiop = &io;
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struct nfsheur *nh;
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MALLOC(ivp, struct iovec *, cnt * sizeof (struct iovec), M_TEMP,
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M_WAITOK);
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@ -733,7 +746,11 @@ nfsvno_write(struct vnode *vp, off_t off, int retlen, int cnt, int stable,
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uiop->uio_segflg = UIO_SYSSPACE;
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NFSUIOPROC(uiop, p);
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uiop->uio_offset = off;
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nh = nfsrv_sequential_heuristic(uiop, vp);
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ioflags |= nh->nh_seqcount << IO_SEQSHIFT;
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error = VOP_WRITE(vp, uiop, ioflags, cred);
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if (error == 0)
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nh->nh_nextoff = uiop->uio_offset;
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FREE((caddr_t)iv, M_TEMP);
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NFSEXITCODE(error);
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@ -107,14 +107,15 @@ FEATURE(nfsserver, "NFS server");
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#define MAX_COMMIT_COUNT (1024 * 1024)
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#define NUM_HEURISTIC 1017
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#define MAX_REORDERED_RPC 16
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#define NUM_HEURISTIC 1031
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#define NHUSE_INIT 64
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#define NHUSE_INC 16
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#define NHUSE_MAX 2048
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static struct nfsheur {
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struct vnode *nh_vp; /* vp to match (unreferenced pointer) */
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off_t nh_nextr; /* next offset for sequential detection */
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off_t nh_nextoff; /* next offset for sequential detection */
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int nh_use; /* use count for selection */
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int nh_seqcount; /* heuristic */
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} nfsheur[NUM_HEURISTIC];
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@ -186,6 +187,63 @@ nfsrv_lockedpair_nd(int vfs1, struct nameidata *nd)
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return nfsrv_lockedpair(vfs1, vfs2);
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}
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/*
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* Heuristic to detect sequential operation.
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*/
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static struct nfsheur *
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nfsrv_sequential_heuristic(struct uio *uio, struct vnode *vp)
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{
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struct nfsheur *nh;
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int hi, try;
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/* Locate best candidate. */
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try = 32;
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hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
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nh = &nfsheur[hi];
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while (try--) {
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if (nfsheur[hi].nh_vp == vp) {
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nh = &nfsheur[hi];
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break;
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}
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if (nfsheur[hi].nh_use > 0)
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--nfsheur[hi].nh_use;
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hi = (hi + 1) % NUM_HEURISTIC;
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if (nfsheur[hi].nh_use < nh->nh_use)
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nh = &nfsheur[hi];
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}
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/* Initialize hint if this is a new file. */
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if (nh->nh_vp != vp) {
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nh->nh_vp = vp;
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nh->nh_nextoff = uio->uio_offset;
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nh->nh_use = NHUSE_INIT;
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if (uio->uio_offset == 0)
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nh->nh_seqcount = 4;
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else
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nh->nh_seqcount = 1;
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}
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/* Calculate heuristic. */
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if ((uio->uio_offset == 0 && nh->nh_seqcount > 0) ||
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uio->uio_offset == nh->nh_nextoff) {
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/* See comments in vfs_vnops.c:sequential_heuristic(). */
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nh->nh_seqcount += howmany(uio->uio_resid, 16384);
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if (nh->nh_seqcount > IO_SEQMAX)
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nh->nh_seqcount = IO_SEQMAX;
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} else if (qabs(uio->uio_offset - nh->nh_nextoff) <= MAX_REORDERED_RPC *
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imax(vp->v_mount->mnt_stat.f_iosize, uio->uio_resid)) {
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/* Probably a reordered RPC, leave seqcount alone. */
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} else if (nh->nh_seqcount > 1) {
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nh->nh_seqcount /= 2;
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} else {
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nh->nh_seqcount = 0;
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}
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nh->nh_use += NHUSE_INC;
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if (nh->nh_use > NHUSE_MAX)
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nh->nh_use = NHUSE_MAX;
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return (nh);
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}
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/*
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* nfs v3 access service
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*/
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@ -843,7 +901,6 @@ nfsrv_read(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
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/*
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* Calculate byte count to read
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*/
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if (off >= vap->va_size)
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cnt = 0;
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else if ((off + reqlen) > vap->va_size)
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@ -851,61 +908,6 @@ nfsrv_read(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
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else
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cnt = reqlen;
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/*
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* Calculate seqcount for heuristic
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*/
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{
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int hi;
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int try = 32;
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/*
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* Locate best candidate
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*/
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hi = ((int)(vm_offset_t)vp / sizeof(struct vnode)) % NUM_HEURISTIC;
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nh = &nfsheur[hi];
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while (try--) {
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if (nfsheur[hi].nh_vp == vp) {
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nh = &nfsheur[hi];
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break;
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}
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if (nfsheur[hi].nh_use > 0)
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--nfsheur[hi].nh_use;
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hi = (hi + 1) % NUM_HEURISTIC;
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if (nfsheur[hi].nh_use < nh->nh_use)
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nh = &nfsheur[hi];
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}
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if (nh->nh_vp != vp) {
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nh->nh_vp = vp;
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nh->nh_nextr = off;
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nh->nh_use = NHUSE_INIT;
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if (off == 0)
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nh->nh_seqcount = 4;
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else
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nh->nh_seqcount = 1;
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}
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/*
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* Calculate heuristic
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*/
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if ((off == 0 && nh->nh_seqcount > 0) || off == nh->nh_nextr) {
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if (++nh->nh_seqcount > IO_SEQMAX)
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nh->nh_seqcount = IO_SEQMAX;
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} else if (nh->nh_seqcount > 1) {
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nh->nh_seqcount = 1;
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} else {
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nh->nh_seqcount = 0;
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}
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nh->nh_use += NHUSE_INC;
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if (nh->nh_use > NHUSE_MAX)
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nh->nh_use = NHUSE_MAX;
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ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
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}
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nfsm_reply(NFSX_POSTOPORFATTR(v3) + 3 * NFSX_UNSIGNED+nfsm_rndup(cnt));
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if (v3) {
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tl = nfsm_build(u_int32_t *, NFSX_V3FATTR + 4 * NFSX_UNSIGNED);
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@ -963,9 +965,11 @@ nfsrv_read(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
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uiop->uio_resid = len;
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uiop->uio_rw = UIO_READ;
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uiop->uio_segflg = UIO_SYSSPACE;
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nh = nfsrv_sequential_heuristic(uiop, vp);
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ioflag |= nh->nh_seqcount << IO_SEQSHIFT;
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error = VOP_READ(vp, uiop, IO_NODELOCKED | ioflag, cred);
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off = uiop->uio_offset;
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nh->nh_nextr = off;
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if (error == 0)
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nh->nh_nextoff = uiop->uio_offset;
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free((caddr_t)iv2, M_TEMP);
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if (error || (getret = VOP_GETATTR(vp, vap, cred))) {
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if (!error)
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@ -1030,6 +1034,7 @@ nfsrv_write(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
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int v3 = (nfsd->nd_flag & ND_NFSV3);
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struct mbuf *mb, *mreq;
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struct vnode *vp = NULL;
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struct nfsheur *nh;
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nfsfh_t nfh;
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fhandle_t *fhp;
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struct uio io, *uiop = &io;
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@ -1170,7 +1175,11 @@ nfsrv_write(struct nfsrv_descript *nfsd, struct nfssvc_sock *slp,
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uiop->uio_segflg = UIO_SYSSPACE;
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uiop->uio_td = NULL;
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uiop->uio_offset = off;
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nh = nfsrv_sequential_heuristic(uiop, vp);
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ioflags |= nh->nh_seqcount << IO_SEQSHIFT;
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error = VOP_WRITE(vp, uiop, ioflags, cred);
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if (error == 0)
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nh->nh_nextoff = uiop->uio_offset;
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/* Unlocked write. */
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nfsrvstats.srvvop_writes++;
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free((caddr_t)iv, M_TEMP);
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