Replace posix-aio with custom thread pool

glibc implements posix-aio as a thread pool and imposes a number of limitations.

1) it limits one request per-file descriptor.  we hack around this by dup()'ing
file descriptors which is hideously ugly

2) it's impossible to add new interfaces and we need a vectored read/write
operation to properly support a zero-copy API.

What has been suggested to me by glibc folks, is to implement whatever new
interfaces we want and then it can eventually be proposed for standardization.
This requires that we implement our own posix-aio implementation though.

This patch implements posix-aio using pthreads.  It immediately eliminates the
need for fd pooling.

It performs at least as well as the current posix-aio code (in some
circumstances, even better).

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5996 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 5 insertions, 15 deletions

diff --git a/configure b/configure
index 13f6358d4c..d1f0c04d80 100755
--- a/configure
+++ b/configure
@@ -149,7 +149,6 @@ FreeBSD)
 bsd="yes"
 audio_drv_list="oss"
 audio_possible_drivers="oss sdl esd pa"
-aio_lib="-lpthread"
 if [ "$cpu" = "i386" -o "$cpu" = "x86_64" ] ; then
     kqemu="yes"
 fi
@@ -159,7 +158,6 @@ bsd="yes"
 audio_drv_list="oss"
 audio_possible_drivers="oss sdl esd"
 oss_lib="-lossaudio"
-aio_lib="-lrt -lpthread"
 ;;
 OpenBSD)
 bsd="yes"
@@ -167,7 +165,6 @@ openbsd="yes"
 audio_drv_list="oss"
 audio_possible_drivers="oss sdl esd"
 oss_lib="-lossaudio"
-aio_lib="-lpthread"
 ;;
 Darwin)
 bsd="yes"
@@ -178,7 +175,6 @@ audio_drv_list="coreaudio"
 audio_possible_drivers="coreaudio sdl fmod"
 OS_CFLAGS="-mdynamic-no-pic"
 OS_LDFLAGS="-framework CoreFoundation -framework IOKit"
-aio_lib="-lpthread"
 ;;
 SunOS)
     solaris="yes"
@@ -527,15 +523,6 @@ if test "$mingw32" = "yes" ; then
     bsd_user="no"
 fi
 
-if [ "$darwin" = "yes" -o "$mingw32" = "yes" ] ; then
-    AIOLIBS=
-elif [ "$bsd" = "yes" ]; then
-    AIOLIBS="$aio_lib"
-else
-    # Some Linux architectures (e.g. s390) don't imply -lpthread automatically.
-    AIOLIBS="-lrt -lpthread"
-fi
-
 if test ! -x "$(which cgcc 2>/dev/null)"; then
     sparse="no"
 fi
@@ -954,14 +941,17 @@ fi
 
 ##########################################
 # AIO probe
+AIOLIBS=""
+
 if test "$aio" = "yes" ; then
   aio=no
   cat > $TMPC << EOF
-#include <aio.h>
-int main(void) { return aio_write(NULL); }
+#include <pthread.h>
+int main(void) { pthread_mutex_t lock; return 0; }
 EOF
   if $cc $ARCH_CFLAGS -o $TMPE $AIOLIBS $TMPC 2> /dev/null ; then
     aio=yes
+    AIOLIBS="-lpthread"
   fi
 fi