[PATCH 0/5] sys_ringbuffer

Kent Overstreet
2024-06-03T00:33:17Z

New syscall for mapping generic ringbuffers for arbitary (supported)
file descriptors.

Ringbuffers can be created either when requested or at file open time,
and can be mapped into multiple address spaces (naturally, since files
can be shared as well).

Initial motivation is for fuse, but I plan on adding support to pipes
and possibly sockets as well - pipes are a particularly interesting use
case, because if both the sender and receiver of a pipe opt in to the
new ringbuffer interface, we can make them the _same_ ringbuffer for
true zero copy IO, while being backwards compatible with existing pipes.

the ringbuffer_wait and ringbuffer_wakeup syscalls are probably going
away in a future iteration, in favor of just using futexes.

In my testing, reading/writing from the ringbuffer 16 bytes at a time is
~7x faster than using read/write syscalls - and I was testing with
mitigations off, real world benefit will be even higher.

Kent Overstreet (5):
darray: lift from bcachefs
darray: Fix darray_for_each_reverse() when darray is empty
fs: sys_ringbuffer
ringbuffer: Test device
ringbuffer: Userspace test helper

MAINTAINERS | 7 +
arch/x86/entry/syscalls/syscall_32.tbl | 3 +
arch/x86/entry/syscalls/syscall_64.tbl | 3 +
fs/Makefile | 2 +
fs/bcachefs/Makefile | 1 -
fs/bcachefs/btree_types.h | 2 +-
fs/bcachefs/btree_update.c | 2 +
fs/bcachefs/btree_write_buffer_types.h | 2 +-
fs/bcachefs/fsck.c | 2 +-
fs/bcachefs/journal_io.h | 2 +-
fs/bcachefs/journal_sb.c | 2 +-
fs/bcachefs/sb-downgrade.c | 3 +-
fs/bcachefs/sb-errors_types.h | 2 +-
fs/bcachefs/sb-members.h | 3 +-
fs/bcachefs/subvolume.h | 1 -
fs/bcachefs/subvolume_types.h | 2 +-
fs/bcachefs/thread_with_file_types.h | 2 +-
fs/bcachefs/util.h | 28 +-
fs/ringbuffer.c | 474 ++++++++++++++++++++++++
fs/ringbuffer_test.c | 209 +++++++++++
{fs/bcachefs => include/linux}/darray.h | 61 +--
include/linux/darray_types.h | 22 ++
include/linux/fs.h | 2 +
include/linux/mm_types.h | 4 +
include/linux/ringbuffer_sys.h | 18 +
include/uapi/linux/futex.h | 1 +
include/uapi/linux/ringbuffer_sys.h | 40 ++
init/Kconfig | 9 +
kernel/fork.c | 2 +
lib/Kconfig.debug | 5 +
lib/Makefile | 2 +-
{fs/bcachefs => lib}/darray.c | 12 +-
tools/ringbuffer/Makefile | 3 +
tools/ringbuffer/ringbuffer-test.c | 254 +++++++++++++
34 files changed, 1125 insertions(+), 62 deletions(-)
create mode 100644 fs/ringbuffer.c
create mode 100644 fs/ringbuffer_test.c
rename {fs/bcachefs => include/linux}/darray.h (63%)
create mode 100644 include/linux/darray_types.h
create mode 100644 include/linux/ringbuffer_sys.h
create mode 100644 include/uapi/linux/ringbuffer_sys.h
rename {fs/bcachefs => lib}/darray.c (56%)
create mode 100644 tools/ringbuffer/Makefile
create mode 100644 tools/ringbuffer/ringbuffer-test.c

--
2.45.1