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Wire O_DIRECT also to Uncached I/O (#17218)

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Before Direct I/O was implemented, I've implemented lighter version
I called Uncached I/O.  It uses normal DMU/ARC data path with some
optimizations, but evicts data from caches as soon as possible and
reasonable.  Originally I wired it only to a primarycache property,
but now completing the integration all the way up to the VFS.

While Direct I/O has the lowest possible memory bandwidth usage,
it also has a significant number of limitations.  It require I/Os
to be page aligned, does not allow speculative prefetch, etc.  The
Uncached I/O does not have those limitations, but instead require
additional memory copy, though still one less than regular cached
I/O.  As such it should fill the gap in between.  Considering this
I've disabled annoying EINVAL errors on misaligned requests, adding
a tunable for those who wants to test their applications.

To pass the information between the layers I had to change a number
of APIs.  But as side effect upper layers can now control not only
the caching, but also speculative prefetch.  I haven't wired it to
VFS yet, since it require looking on some OS specifics.  But while
there I've implemented speculative prefetch of indirect blocks for
Direct I/O, controllable via all the same mechanisms.

Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Fixes #17027
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Alexander Motin
2025-05-13 17:26:55 -04:00
committed by GitHub
parent e2ba0f7643
commit 734eba251d
35 changed files with 397 additions and 294 deletions
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include/sys/dbuf.h
+7 -18
View File
@@ -45,20 +45,6 @@ extern "C" {
#define IN_DMU_SYNC 2
/*
* define flags for dbuf_read
*/
#define DB_RF_MUST_SUCCEED (1 << 0)
#define DB_RF_CANFAIL (1 << 1)
#define DB_RF_HAVESTRUCT (1 << 2)
#define DB_RF_NOPREFETCH (1 << 3)
#define DB_RF_NEVERWAIT (1 << 4)
#define DB_RF_CACHED (1 << 5)
#define DB_RF_NO_DECRYPT (1 << 6)
#define DB_RF_PARTIAL_FIRST (1 << 7)
#define DB_RF_PARTIAL_MORE (1 << 8)
/*
* The simplified state transition diagram for dbufs looks like:
*
@@ -389,12 +375,15 @@ void dbuf_rele_and_unlock(dmu_buf_impl_t *db, const void *tag,
dmu_buf_impl_t *dbuf_find(struct objset *os, uint64_t object, uint8_t level,
uint64_t blkid, uint64_t *hash_out);
int dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags);
int dbuf_read(dmu_buf_impl_t *db, zio_t *zio, dmu_flags_t flags);
void dmu_buf_will_clone_or_dio(dmu_buf_t *db, dmu_tx_t *tx);
void dmu_buf_will_not_fill(dmu_buf_t *db, dmu_tx_t *tx);
void dmu_buf_will_fill(dmu_buf_t *db, dmu_tx_t *tx, boolean_t canfail);
void dmu_buf_will_fill_flags(dmu_buf_t *db, dmu_tx_t *tx, boolean_t canfail,
dmu_flags_t flags);
boolean_t dmu_buf_fill_done(dmu_buf_t *db, dmu_tx_t *tx, boolean_t failed);
void dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx);
void dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx,
dmu_flags_t flags);
dbuf_dirty_record_t *dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx);
dbuf_dirty_record_t *dbuf_dirty_lightweight(dnode_t *dn, uint64_t blkid,
dmu_tx_t *tx);
@@ -475,10 +464,10 @@ dbuf_find_dirty_eq(dmu_buf_impl_t *db, uint64_t txg)
#define DBUF_GET_BUFC_TYPE(_db) \
(dbuf_is_metadata(_db) ? ARC_BUFC_METADATA : ARC_BUFC_DATA)
#define DBUF_IS_CACHEABLE(_db) \
#define DBUF_IS_CACHEABLE(_db) (!(_db)->db_pending_evict && \
((_db)->db_objset->os_primary_cache == ZFS_CACHE_ALL || \
(dbuf_is_metadata(_db) && \
((_db)->db_objset->os_primary_cache == ZFS_CACHE_METADATA)))
((_db)->db_objset->os_primary_cache == ZFS_CACHE_METADATA))))
boolean_t dbuf_is_l2cacheable(dmu_buf_impl_t *db, blkptr_t *db_bp);