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| author | Alexander Motin <mav@FreeBSD.org> | 2017-11-20 19:56:01 +0200 |
|---|---|---|
| committer | Prakash Surya <prakash.surya@delphix.com> | 2018-01-18 09:07:03 -0800 |
| commit | 5cb8d943bc8513c6230589aad5a409d58b0297cb (patch) | |
| tree | 8411a5f0c755377ad142ed8582b631ff7a814056 | |
| parent | 4ae5f5f06c6c2d1db8167480f7d9e3b5378ba2f2 (diff) | |
| download | illumos-joyent-5cb8d943bc8513c6230589aad5a409d58b0297cb.tar.gz | |
8835 Speculative prefetch in ZFS not working for misaligned reads
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Allan Jude <allanjude@freebsd.org>
Approved by: Gordon Ross <gwr@nexenta.com>
| -rw-r--r-- | usr/src/uts/common/fs/zfs/dmu_zfetch.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/usr/src/uts/common/fs/zfs/dmu_zfetch.c b/usr/src/uts/common/fs/zfs/dmu_zfetch.c index 5d5c478627..5d6f20d072 100644 --- a/usr/src/uts/common/fs/zfs/dmu_zfetch.c +++ b/usr/src/uts/common/fs/zfs/dmu_zfetch.c @@ -235,19 +235,33 @@ dmu_zfetch(zfetch_t *zf, uint64_t blkid, uint64_t nblks, boolean_t fetch_data) rw_enter(&zf->zf_rwlock, RW_READER); + /* + * Find matching prefetch stream. Depending on whether the accesses + * are block-aligned, first block of the new access may either follow + * the last block of the previous access, or be equal to it. + */ for (zs = list_head(&zf->zf_stream); zs != NULL; zs = list_next(&zf->zf_stream, zs)) { - if (blkid == zs->zs_blkid) { + if (blkid == zs->zs_blkid || blkid + 1 == zs->zs_blkid) { mutex_enter(&zs->zs_lock); /* * zs_blkid could have changed before we * acquired zs_lock; re-check them here. */ - if (blkid != zs->zs_blkid) { - mutex_exit(&zs->zs_lock); - continue; + if (blkid == zs->zs_blkid) { + break; + } else if (blkid + 1 == zs->zs_blkid) { + blkid++; + nblks--; + if (nblks == 0) { + /* Already prefetched this before. */ + mutex_exit(&zs->zs_lock); + rw_exit(&zf->zf_rwlock); + return; + } + break; } - break; + mutex_exit(&zs->zs_lock); } } |