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Relax zfs_vnops_read_chunk_size limitations #17415

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Merged
merged 1 commit into from
Jun 4, 2025
Merged

Relax zfs_vnops_read_chunk_size limitations #17415

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2 changes: 1 addition & 1 deletion man/man4/zfs.4
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Original file line number Diff line number Diff line change
Expand Up @@ -1980,7 +1980,7 @@ Disable QAT hardware acceleration for AES-GCM encryption.
May be unset after the ZFS modules have been loaded to initialize the QAT
hardware as long as support is compiled in and the QAT driver is present.
.
.It Sy zfs_vnops_read_chunk_size Ns = Ns Sy 1048576 Ns B Po 1 MiB Pc Pq u64
.It Sy zfs_vnops_read_chunk_size Ns = Ns Sy 33554432 Ns B Po 32 MiB Pc Pq u64
Bytes to read per chunk.
.
.It Sy zfs_read_history Ns = Ns Sy 0 Pq uint
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12 changes: 10 additions & 2 deletions module/zfs/zfs_vnops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -99,7 +99,11 @@ static int zfs_dio_strict = 0;
/*
* Maximum bytes to read per chunk in zfs_read().
*/
#ifdef _ILP32
static uint64_t zfs_vnops_read_chunk_size = 1024 * 1024;
#else
static uint64_t zfs_vnops_read_chunk_size = DMU_MAX_ACCESS / 2;
#endif

int
zfs_fsync(znode_t *zp, int syncflag, cred_t *cr)
Expand Down Expand Up @@ -401,7 +405,8 @@ zfs_read(struct znode *zp, zfs_uio_t *uio, int ioflag, cred_t *cr)
#if defined(__linux__)
ssize_t start_offset = zfs_uio_offset(uio);
#endif
ssize_t chunk_size = zfs_vnops_read_chunk_size;
uint_t blksz = zp->z_blksz;
ssize_t chunk_size;
ssize_t n = MIN(zfs_uio_resid(uio), zp->z_size - zfs_uio_offset(uio));
ssize_t start_resid = n;
ssize_t dio_remaining_resid = 0;
Expand Down Expand Up @@ -432,11 +437,14 @@ zfs_read(struct znode *zp, zfs_uio_t *uio, int ioflag, cred_t *cr)
if (dio_remaining_resid != 0)
n -= dio_remaining_resid;
dflags |= DMU_DIRECTIO;
} else {
chunk_size = MIN(MAX(zfs_vnops_read_chunk_size, blksz),
DMU_MAX_ACCESS / 2);
}

while (n > 0) {
ssize_t nbytes = MIN(n, chunk_size -
P2PHASE(zfs_uio_offset(uio), chunk_size));
P2PHASE(zfs_uio_offset(uio), blksz));
#ifdef UIO_NOCOPY
if (zfs_uio_segflg(uio) == UIO_NOCOPY)
error = mappedread_sf(zp, nbytes, uio);
Expand Down