diff options
| author | Thomas Munro | 2021-07-18 20:52:00 +0000 |
|---|---|---|
| committer | Thomas Munro | 2021-07-18 23:01:01 +0000 |
| commit | 2dbe8905711ba09a2214b6e835f8f0c2c4981cb3 (patch) | |
| tree | 775e44cb05c4dfa8f12e68eb388f04e9aa252c96 /src/include | |
| parent | f157db862225a7bfe041ca3f7b73e913e2a8d8d6 (diff) | |
Support direct I/O on macOS.
Macs don't understand O_DIRECT, but they can disable caching with a
separate fcntl() call. Extend the file opening functions in fd.c to
handle this for us if the caller passes in PG_O_DIRECT.
For now, this affects only WAL data and even then only if you set:
max_wal_senders=0
wal_level=minimal
This is not expected to be very useful on its own, but later proposed
patches will make greater use of direct I/O, and it'll be useful for
testing if developers on Macs can see the effects.
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA%2BhUKG%2BADiyyHe0cun2wfT%2BSVnFVqNYPxoO6J9zcZkVO7%2BNGig%40mail.gmail.com
Diffstat (limited to 'src/include')
| -rw-r--r-- | src/include/access/xlogdefs.h | 15 | ||||
| -rw-r--r-- | src/include/storage/fd.h | 16 |
2 files changed, 16 insertions, 15 deletions
diff --git a/src/include/access/xlogdefs.h b/src/include/access/xlogdefs.h index 0940b64ca6b..60348d18509 100644 --- a/src/include/access/xlogdefs.h +++ b/src/include/access/xlogdefs.h @@ -65,21 +65,6 @@ typedef uint32 TimeLineID; typedef uint16 RepOriginId; /* - * Because O_DIRECT bypasses the kernel buffers, and because we never - * read those buffers except during crash recovery or if wal_level != minimal, - * it is a win to use it in all cases where we sync on each write(). We could - * allow O_DIRECT with fsync(), but it is unclear if fsync() could process - * writes not buffered in the kernel. Also, O_DIRECT is never enough to force - * data to the drives, it merely tries to bypass the kernel cache, so we still - * need O_SYNC/O_DSYNC. - */ -#ifdef O_DIRECT -#define PG_O_DIRECT O_DIRECT -#else -#define PG_O_DIRECT 0 -#endif - -/* * This chunk of hackery attempts to determine which file sync methods * are available on the current platform, and to choose an appropriate * default method. We assume that fsync() is always available, and that diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h index 5b3c280dd7a..2d843eb9929 100644 --- a/src/include/storage/fd.h +++ b/src/include/storage/fd.h @@ -80,6 +80,22 @@ extern int max_safe_fds; #endif /* + * O_DIRECT is not standard, but almost every Unix has it. We translate it + * to the appropriate Windows flag in src/port/open.c. We simulate it with + * fcntl(F_NOCACHE) on macOS inside fd.c's open() wrapper. We use the name + * PG_O_DIRECT rather than defining O_DIRECT in that case (probably not a good + * idea on a Unix). + */ +#if defined(O_DIRECT) +#define PG_O_DIRECT O_DIRECT +#elif defined(F_NOCACHE) +#define PG_O_DIRECT 0x80000000 +#define PG_O_DIRECT_USE_F_NOCACHE +#else +#define PG_O_DIRECT 0 +#endif + +/* * prototypes for functions in fd.c */ |