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Store a hint in the nfsnode to detect sequential access of the file.

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Kick off a readahead only when sequential access is detected.  This
eliminates wasteful readaheads in random file access.

Submitted by:	Mohan Srinivasan mohans at yahoo-inc dot com
Obtained from:	Yahoo!
This commit is contained in:
ps 2004-12-10 03:27:12 +00:00
parent f104772590
commit f46c52047f
3 changed files with 6 additions and 1 deletions
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5
sys/nfsclient/nfs_bio.c
View File

@ -421,8 +421,10 @@ nfs_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
/* /*
* Start the read ahead(s), as required. * Start the read ahead(s), as required.
* The readahead is kicked off only if sequential access
* is detected, based on the readahead hint (ra_expect_lbn).
*/ */
if (nmp->nm_readahead > 0) { if (nmp->nm_readahead > 0 && np->ra_expect_lbn == lbn) {
for (nra = 0; nra < nmp->nm_readahead && nra < seqcount && for (nra = 0; nra < nmp->nm_readahead && nra < seqcount &&
(off_t)(lbn + 1 + nra) * biosize < np->n_size; nra++) { (off_t)(lbn + 1 + nra) * biosize < np->n_size; nra++) {
rabn = lbn + 1 + nra; rabn = lbn + 1 + nra;
@ -448,6 +450,7 @@ nfs_bioread(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *cred)
} }
} }
} }
np->ra_expect_lbn = lbn + 1;
} }
/* /*

1
sys/nfsclient/nfs_vnops.c
View File

@ -434,6 +434,7 @@ nfs_open(struct vop_open_args *ap)
np->n_mtime = vattr.va_mtime; np->n_mtime = vattr.va_mtime;
} }
} }
np->ra_expect_lbn = 0;
return (0); return (0);
} }

1
sys/nfsclient/nfsnode.h
View File

@ -126,6 +126,7 @@ struct nfsnode {
struct nfs4_fctx n_wfc; struct nfs4_fctx n_wfc;
u_char *n_name; /* leaf name, for v4 OPEN op */ u_char *n_name; /* leaf name, for v4 OPEN op */
uint32_t n_namelen; uint32_t n_namelen;
daddr_t ra_expect_lbn;
}; };
#define n_atim n_un1.nf_atim #define n_atim n_un1.nf_atim