[PATCH 0/6] v2: Asynchronous function calls to speed up booting and more

[Arjan van de Ven <arjan@infradead.org>]

Hi,

Changes since last version
* some tweaks to the bootchart script to get better visualization
* added serialization points in the irq autodetector, module unloading
  and at rootfs mounting (based on feedback from Linus and Andi)
* added a second libata patch to scan the partition tables from inside
  the async code, without global serialization (based on Linus
  suggestion). This saves a ton of boot time for my box with 2 sata
  controllers

I talked to David Howells to see if we could share the thread pool code
(all 35 lines of it), but his requirements are more or less
incompatible with mine. He needs priorities to be honored, while I need
to do strict sequencing of events, and this appears to be hardly
compatible, at least not without adding much more complexity than the
relatively simple thread code justifies.

parts of the original announcement below; I've updated the two
bootcharts with the new code; basically my testbox is going from 2.75
seconds to 1.0 seconds (approximately).. which is not a bad gain at all.

I've also stuck the patches in a git tree; the git info is:

The following changes since commit 238c6d54830c624f34ac9cf123ac04aebfca5013:
  Linus Torvalds (1):
        Merge git://git.kernel.org/.../agk/linux-2.6-dm

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/arjan/linux-2.6-async.git master

Arjan van de Ven (6):
      fastboot: Asynchronous function calls to speed up kernel boot
      fastboot: make scsi probes asynchronous
      fastboot: make the libata port scan asynchronous
      fastboot: make ACPI bus drivers probe asynchronous
      bootchart: improve output based on Dave Jones' feedback
      fastboot: Make libata initialization even more async

 drivers/acpi/scan.c       |   23 +++-
 drivers/ata/libata-core.c |   96 ++++++++-------
 drivers/scsi/scsi_scan.c  |    3 +
 drivers/scsi/sd.c         |  109 ++++++++++------
 include/linux/async.h     |   21 +++
 init/do_mounts.c          |    2 +
 init/main.c               |    5 +-
 kernel/Makefile           |    3 +-
 kernel/async.c            |  307 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/irq/autoprobe.c    |    5 +
 kernel/module.c           |    2 +
 scripts/bootgraph.pl      |   16 ++-
 12 files changed, 491 insertions(+), 101 deletions(-)
 create mode 100644 include/linux/async.h
 create mode 100644 kernel/async.c


should this go via -tip? is the first patch simple enough for .29 so that the later ones can go via the maintainer trees after that?


=====

This patch series introduces asynchronous function calls.
The goal is still the same (boot faster), the method is entirely
different.

Asynchronous function calls allow drivers and subsystems to do
operations asynchronously, while providing a mechanism to serialize
the asynchronous operations at "externally visible" locations, such as
device number registrations. 

As such, this approach is NOT a "full parallel kernel init".
For one, it keeps device numbers stable. For another, it's very much
opt-in for any code using this.

Rather, it is more comparable to an out-of-order cpu, where computations
are done asynchronously, but are retired in program order.

This series first introduces the infrastructure in patch 1,
and then adds users of this infrastructure (scsi in patch2, libata in
patch 3 and acpi in patch 4).

To see this working, I uploaded a "before" and "after" kernel bootchart
for one of my testboxes at

http://www.kernel.org/pub/linux/kernel/people/arjan/async/before.svg
http://www.kernel.org/pub/linux/kernel/people/arjan/async/after.svg

[minor note; the "after" one also has Alan's suggestion to tweak the
serial config option]

As you can see with inkscape (or gimp or any other svg viewer), there
is still some room for doing more things in parallel, but the 3 example
usage patches are a big win already.


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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