linux-toradex.git/include/linux/aio.h, branch v2.6.22.7

signal/timer/event: KAIO eventfd support example

2007-05-11T15:29:37+00:00

This is an example about how to add eventfd support to the current KAIO code,
in order to enable KAIO to post readiness events to a pollable fd (hence
compatible with POSIX select/poll).  The KAIO code simply signals the eventfd
fd when events are ready, and this triggers a POLLIN in the fd.  This patch
uses a reserved for future use member of the struct iocb to pass an eventfd
file descriptor, that KAIO will use to post events every time a request
completes.  At that point, an aio_getevents() will return the completed result
to a struct io_event.  I made a quick test program to verify the patch, and it
runs fine here:

http://www.xmailserver.org/eventfd-aio-test.c

The test program uses poll(2), but it'd, of course, work with select and epoll
too.

This can allow to schedule both block I/O and other poll-able devices
requests, and wait for results using select/poll/epoll.  In a typical
scenario, an application would submit KAIO request using aio_submit(), and
will also use epoll_ctl() on the whole other class of devices (that with the
addition of signals, timers and user events, now it's pretty much complete),
and then would:

	epoll_wait(...);
	for_each_event {
		if (curr_event_is_kaiofd) {
			aio_getevents();
			dispatch_aio_events();
		} else {
			dispatch_epoll_event();
		}
	}

Signed-off-by: Davide Libenzi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aio is unlikely

2007-05-09T19:30:54+00:00

Stick an unlikely() around is_aio(): I assert that most IO is synchronous.

Cc: Suparna Bhattacharya 
Cc: Ingo Molnar 
Cc: Benjamin LaHaise 
Cc: Zach Brown 
Cc: Ulrich Drepper 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] optimize o_direct on block devices

2006-12-13T17:05:50+00:00

Implement block device specific .direct_IO method instead of going through
generic direct_io_worker for block device.

direct_io_worker() is fairly complex because it needs to handle O_DIRECT on
file system, where it needs to perform block allocation, hole detection,
extents file on write, and tons of other corner cases.  The end result is
that it takes tons of CPU time to submit an I/O.

For block device, the block allocation is much simpler and a tight triple
loop can be written to iterate each iovec and each page within the iovec in
order to construct/prepare bio structure and then subsequently submit it to
the block layer.  This significantly speeds up O_D on block device.

[akpm@osdl.org: small speedup]
Signed-off-by: Ken Chen 
Cc: Christoph Hellwig 
Cc: Zach Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] aio: remove ki_retried debugging member

2006-12-07T16:39:46+00:00

Remove the ki_retried member from struct kiocb.  I think the idea was
bounced around a while back, but Arnaldo pointed out another reason that we
should dig it up when he pointed out that the last cacheline of struct
kiocb only contains 4 bytes.  By removing the debugging member, we save
more than the 8 byte on 64 bit machines.

Signed-off-by: Benjamin LaHaise 
Acked-by: Ken Chen 
Acked-by: Zach Brown 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

WorkStruct: Separate delayable and non-delayable events.

2006-11-22T14:54:01+00:00

Separate delayable work items from non-delayable work items be splitting them
into a separate structure (delayed_work), which incorporates a work_struct and
the timer_list removed from work_struct.

The work_struct struct is huge, and this limits it's usefulness.  On a 64-bit
architecture it's nearly 100 bytes in size.  This reduces that by half for the
non-delayable type of event.

Signed-Off-By: David Howells

[PATCH] clean up unused kiocb variables

2006-10-01T07:39:29+00:00

Signed-off-by: Ken Chen 
Acked-by: Zach Brown 
Cc: Suparna Bhattacharya 
Cc: Benjamin LaHaise 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Add vector AIO support

2006-10-01T07:39:29+00:00

This work is initially done by Zach Brown to add support for vectored aio.
These are the core changes for AIO to support
IOCB_CMD_PREADV/IOCB_CMD_PWRITEV.

[akpm@osdl.org: huge build fix]
Signed-off-by: Zach Brown 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Badari Pulavarty 
Acked-by: Benjamin LaHaise 
Acked-by: James Morris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Vectorize aio_read/aio_write fileop methods

2006-10-01T07:39:28+00:00

This patch vectorizes aio_read() and aio_write() methods to prepare for
collapsing all aio & vectored operations into one interface - which is
aio_read()/aio_write().

Signed-off-by: Badari Pulavarty 
Signed-off-by: Christoph Hellwig 
Cc: Michael Holzheu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] Remove BUG_ON(unlikely) in include/linux/aio.h

2006-10-01T07:39:24+00:00

BUG_ON() does this unlikely check itself, as bugs in Linux are unlikely
anyway :)

Signed-off-by: Rolf Eike Beer 
Acked-by: Zach Brown 
Acked-by: Benjamin LaHaise 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] aio: reorder kiocb structure elements to make sync iocb setup faster

2006-01-09T04:14:03+00:00

Reorder members of the kiocb structure to make sync kiocb setup faster.  By
setting the elements sequentially, the write combining buffers on the CPU
are able to combine the writes into a single burst, which results in fewer
cache cycles being consumed, freeing them up for other code.  This results
in a 10-20KB/s[*] increase on the bw_unix part of LMbench on my test
system.

* The improvement varies based on what other patches are in the system,
  as there are a number of bottlenecks, so this number is not absolutely
  accurate.

Signed-off-by: Benjamin LaHaise 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds