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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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module/zfs/dmu_direct.c
+8 -6
View File
@@ -208,7 +208,7 @@ dmu_write_direct(zio_t *pio, dmu_buf_impl_t *db, abd_t *data, dmu_tx_t *tx)
int
dmu_write_abd(dnode_t *dn, uint64_t offset, uint64_t size,
abd_t *data, uint32_t flags, dmu_tx_t *tx)
abd_t *data, dmu_flags_t flags, dmu_tx_t *tx)
{
dmu_buf_t **dbp;
spa_t *spa = dn->dn_objset->os_spa;
@@ -247,7 +247,7 @@ dmu_write_abd(dnode_t *dn, uint64_t offset, uint64_t size,
int
dmu_read_abd(dnode_t *dn, uint64_t offset, uint64_t size,
abd_t *data, uint32_t flags)
abd_t *data, dmu_flags_t flags)
{
objset_t *os = dn->dn_objset;
spa_t *spa = os->os_spa;
@@ -351,7 +351,8 @@ error:
#ifdef _KERNEL
int
dmu_read_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size)
dmu_read_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size,
dmu_flags_t flags)
{
offset_t offset = zfs_uio_offset(uio);
offset_t page_index = (offset - zfs_uio_soffset(uio)) >> PAGESHIFT;
@@ -362,7 +363,7 @@ dmu_read_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size)
abd_t *data = abd_alloc_from_pages(&uio->uio_dio.pages[page_index],
offset & (PAGESIZE - 1), size);
err = dmu_read_abd(dn, offset, size, data, DMU_DIRECTIO);
err = dmu_read_abd(dn, offset, size, data, flags);
abd_free(data);
if (err == 0)
@@ -372,7 +373,8 @@ dmu_read_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size)
}
int
dmu_write_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size, dmu_tx_t *tx)
dmu_write_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size,
dmu_flags_t flags, dmu_tx_t *tx)
{
offset_t offset = zfs_uio_offset(uio);
offset_t page_index = (offset - zfs_uio_soffset(uio)) >> PAGESHIFT;
@@ -383,7 +385,7 @@ dmu_write_uio_direct(dnode_t *dn, zfs_uio_t *uio, uint64_t size, dmu_tx_t *tx)
abd_t *data = abd_alloc_from_pages(&uio->uio_dio.pages[page_index],
offset & (PAGESIZE - 1), size);
err = dmu_write_abd(dn, offset, size, data, DMU_DIRECTIO, tx);
err = dmu_write_abd(dn, offset, size, data, flags, tx);
abd_free(data);
if (err == 0)