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Re: [Qemu-devel] [PATCH v6 0/5] Coroutines for better asynchronous progr
From: |
Blue Swirl |
Subject: |
Re: [Qemu-devel] [PATCH v6 0/5] Coroutines for better asynchronous programming |
Date: |
Sat, 16 Jul 2011 13:08:55 +0300 |
On Mon, Jun 27, 2011 at 12:21 PM, Stefan Hajnoczi <address@hidden> wrote:
> Here is the latest version of the coroutine series with Mac OS X fixes from
> Andreas Färber <address@hidden>.
>
> QEMU is event-driven and suffers when blocking operations are performed
> because
> VM execution may be stopped until the operation completes. Therefore many
> operations that could block are performed asynchronously and a callback is
> invoked when the operation has completed. This allows QEMU to continue
> executing while the operation is pending.
>
> The downside to callbacks is that they split up code into many smaller
> functions, each of which is a single step in a state machine that quickly
> becomes complex and hard to understand. Callback functions also result in
> lots
> of noise as variables are packed and unpacked into temporary structs that pass
> state to the callback function.
>
> This patch series introduces coroutines as a solution for writing asynchronous
> code while still having a nice sequential control flow. The semantics are
> explained in the second patch. The fourth patch adds automated tests.
>
> A nice feature of coroutines is that it is relatively easy to take synchronous
> code and lift it into a coroutine to make it asynchronous. Work has been done
> to move qcow2 request processing into coroutines and thereby make it
> asynchronous (today qcow2 will perform synchronous metadata accesses). This
> qcow2 work is still ongoing and not quite ready for mainline yet.
>
> Coroutines are also being used for virtfs (virtio-9p) so I have submitted this
> patch now because virtfs patches that depend on coroutines are being
> published.
Coroutines seem to work fine on OpenBSD (Sparc64, also tests are
passed) and mingw32, with a few minor issues.
With simpletrace enabled there is a link failure:
$ make test-coroutine
LINK test-coroutine
simpletrace.o: In function `get_clock':
/src/qemu/qemu-timer.h:117: undefined reference to `use_rt_clock'
This can be fixed for example by adding qemu-timer-common.o to the
list of linked objects.
I can't compile coroutine tests for Mingw32 because of this:
$ make test-coroutine
CC test-coroutine.o
In file included from
/usr/local/i686-mingw32msvc/include/glib-2.0/glib/galloca.h:30:0,
from /usr/local/i686-mingw32msvc/include/glib-2.0/glib.h:30,
from /src/qemu/test-coroutine.c:14:
/usr/local/i686-mingw32msvc/include/glib-2.0/glib/gtypes.h:30:24:
fatal error: glibconfig.h: No such file or directory
I used glib win32 zips from
http://ftp.gnome.org/pub/gnome/binaries/win32/glib/2.12/, is there a
better site? Otherwise QEMU builds fine and runs under Wine nicely.
> v6:
> * Use GThread on Mac OS X, fix from Andreas Färber <address@hidden>
> * abort(3) if coroutine-ucontext.c fails to create a coroutine
>
> v5:
> * GThread-based implementation for platforms without makecontext(3) (Aneesh
> Kumar K.V <address@hidden>)
> * Switch to gtester test framework
>
> v4:
> * Windows Fibers support (Paolo Bonzini <address@hidden>)
> * Return-after-setjmp() fix (Aneesh Kumar K.V <address@hidden>)
> * Re-entrancy for multi-threaded coroutines support
> * qemu-coroutine.h cleanup and documentation
>
> v3:
> * Updated LGPL v2 license header to use web link
> * Removed atexit(3) pool freeing
> * Removed thread-local current/leader
> * Documented thread-safety limitation
> * Disabled trace events
>
> v2:
> * Added ./check-coroutine --lifecycle-benchmark for performance measurement
> * Split pooling into a separate patch with performance justification
> * Set maximum pool size to prevent holding onto too many free coroutines
> * Added atexit(3) handler to free pool
> * Coding style cleanups
>
> Aneesh Kumar K.V (1):
> coroutine: implement coroutines using gthread
>
> Anthony Liguori (1):
> Add hard build dependency on glib
>
> Kevin Wolf (1):
> coroutine: introduce coroutines
>
> Stefan Hajnoczi (2):
> coroutine: add test-coroutine automated tests
> coroutine: add test-coroutine --benchmark-lifecycle
>
> .gitignore | 1 +
> Makefile | 5 +-
> Makefile.objs | 13 +++
> Makefile.target | 1 +
> configure | 31 +++++++
> coroutine-gthread.c | 131 ++++++++++++++++++++++++++++
> coroutine-ucontext.c | 230
> ++++++++++++++++++++++++++++++++++++++++++++++++++
> coroutine-win32.c | 92 ++++++++++++++++++++
> qemu-coroutine-int.h | 48 +++++++++++
> qemu-coroutine.c | 75 ++++++++++++++++
> qemu-coroutine.h | 95 +++++++++++++++++++++
> test-coroutine.c | 192 +++++++++++++++++++++++++++++++++++++++++
> trace-events | 5 +
> 13 files changed, 918 insertions(+), 1 deletions(-)
> create mode 100644 coroutine-gthread.c
> create mode 100644 coroutine-ucontext.c
> create mode 100644 coroutine-win32.c
> create mode 100644 qemu-coroutine-int.h
> create mode 100644 qemu-coroutine.c
> create mode 100644 qemu-coroutine.h
> create mode 100644 test-coroutine.c
>
> --
> 1.7.5.4
>
>
>
- Re: [Qemu-devel] [PATCH v6 0/5] Coroutines for better asynchronous programming,
Blue Swirl <=