On Thu, Oct 15, 2020 at 11:26:07AM -0700, Darrick J. Wong wrote: > On Thu, Oct 15, 2020 at 06:21:55PM +1100, Dave Chinner wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > Simple per-ag thread based completion engine. Will have issues with > > large AG counts. > > Hm, I missed how any of this is per-AG... all I saw was an aio control > context that's attached to the buftarg. Stale - I got rid of the per-ag AIO structures because having 500 completion threads in gdb is a PITA and it provided no better performance. i.e. it had problems with large AG counts. > > XXX: should this be combined with the struct btcache? > > > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > > --- > > include/atomic.h | 7 +- > > include/builddefs.in | 2 +- > > include/platform_defs.h.in | 1 + > > libxfs/buftarg.c | 202 +++++++++++++++++++++++++++++++------ > > libxfs/xfs_buf.h | 6 ++ > > libxfs/xfs_buftarg.h | 7 ++ > > 6 files changed, 191 insertions(+), 34 deletions(-) > > > > diff --git a/include/atomic.h b/include/atomic.h > > index 5860d7897ae5..8727fc4ddae9 100644 > > --- a/include/atomic.h > > +++ b/include/atomic.h > > @@ -27,8 +27,11 @@ typedef int64_t atomic64_t; > > #define atomic_inc_return(a) uatomic_add_return(a, 1) > > #define atomic_dec_return(a) uatomic_sub_return(a, 1) > > > > -#define atomic_inc(a) atomic_inc_return(a) > > -#define atomic_dec(a) atomic_inc_return(a) > > +#define atomic_add(a, v) uatomic_add(a, v) > > +#define atomic_sub(a, v) uatomic_sub(a, v) > > + > > +#define atomic_inc(a) uatomic_inc(a) > > +#define atomic_dec(a) uatomic_dec(a) > > Does this belong in the liburcu patch? Probably. > > > > > #define atomic_dec_and_test(a) (atomic_dec_return(a) == 0) > > > > diff --git a/include/builddefs.in b/include/builddefs.in > > index 78eddf4a9852..c20a48f6258c 100644 > > --- a/include/builddefs.in > > +++ b/include/builddefs.in > > @@ -29,7 +29,7 @@ LIBEDITLINE = @libeditline@ > > LIBBLKID = @libblkid@ > > LIBDEVMAPPER = @libdevmapper@ > > LIBINIH = @libinih@ > > -LIBXFS = $(TOPDIR)/libxfs/libxfs.la > > +LIBXFS = $(TOPDIR)/libxfs/libxfs.la -laio > > This needs all the autoconf magic to complain if libaio isn't installed, > right? Yes. > > /* > > - * This is a bit of a hack until we get AIO that runs completions. > > - * Success is treated as a completion here, but IO errors are handled as > > - * a submission error and are handled by the caller. AIO will clean this > > - * up. > > + * don't overwrite existing errors - otherwise we can lose errors on > > + * buffers that require multiple bios to complete. > > + * > > + * We check that the returned length was the same as specified for this > > + * IO. Note that this onyl works for read and write - if we start > > + * using readv/writev for discontiguous buffers then this needs more > > + * work. > > Interesting RFC, though I gather discontig buffers don't work yet? Right they don't work yet. I mention that in a couple of places. > Or hmm maybe there's something funny going on with > xfs_buftarg_submit_io_map? You didn't post a git branch link, so it's > hard(er) to just rummage around on my own. :/ > > This seems like a reasonable restructuring to allow asynchronous io. > It's sort of a pity that this isn't modular enough to allow multiple IO > engines (synchronous system calls and io_uring come to mine) but that > can come later. Making it modular is easy enough, but that can be done independently of this buffer cache enabling patchset. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
