coroutine: add ./configure --disable-coroutine-pool
The 'gthread' coroutine backend was written before the freelist (aka
pool) existed in qemu-coroutine.c.
This means that every thread is expected to exit when its coroutine
terminates. It is not possible to reuse threads from a pool.
This patch automatically disables the pool when 'gthread' is used. This
allows the 'gthread' backend to work again (for example,
tests/test-coroutine completes successfully instead of hanging).
I considered implementing thread reuse but I don't want quirks like CPU
affinity differences due to coroutine threads being recycled. The
'gthread' backend is a reference backend and it's therefore okay to skip
the pool optimization.
Note this patch also makes it easy to toggle the pool for benchmarking
purposes:
./configure --with-coroutine-backend=ucontext \
--disable-coroutine-pool
Reported-by: Gabriel Kerneis <gabriel@kerneis.info>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Gabriel Kerneis <gabriel@kerneis.info>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/configure b/configure
index b499028..1b6f68b 100755
--- a/configure
+++ b/configure
@@ -238,6 +238,7 @@
want_tools="yes"
libiscsi=""
coroutine=""
+coroutine_pool=""
seccomp=""
glusterfs=""
glusterfs_discard="no"
@@ -888,6 +889,10 @@
;;
--with-coroutine=*) coroutine="$optarg"
;;
+ --disable-coroutine-pool) coroutine_pool="no"
+ ;;
+ --enable-coroutine-pool) coroutine_pool="yes"
+ ;;
--disable-docs) docs="no"
;;
--enable-docs) docs="yes"
@@ -1189,6 +1194,8 @@
echo " --enable-seccomp enables seccomp support"
echo " --with-coroutine=BACKEND coroutine backend. Supported options:"
echo " gthread, ucontext, sigaltstack, windows"
+echo " --disable-coroutine-pool disable coroutine freelist (worse performance)"
+echo " --enable-coroutine-pool enable coroutine freelist (better performance)"
echo " --enable-glusterfs enable GlusterFS backend"
echo " --disable-glusterfs disable GlusterFS backend"
echo " --enable-gcov enable test coverage analysis with gcov"
@@ -3362,6 +3369,17 @@
esac
fi
+if test "$coroutine_pool" = ""; then
+ if test "$coroutine" = "gthread"; then
+ coroutine_pool=no
+ else
+ coroutine_pool=yes
+ fi
+fi
+if test "$coroutine" = "gthread" -a "$coroutine_pool" = "yes"; then
+ error_exit "'gthread' coroutine backend does not support pool (use --disable-coroutine-pool)"
+fi
+
##########################################
# check if we have open_by_handle_at
@@ -3733,6 +3751,7 @@
echo "QGA VSS support $guest_agent_with_vss"
echo "seccomp support $seccomp"
echo "coroutine backend $coroutine"
+echo "coroutine pool $coroutine_pool"
echo "GlusterFS support $glusterfs"
echo "virtio-blk-data-plane $virtio_blk_data_plane"
echo "gcov $gcov_tool"
@@ -4092,6 +4111,11 @@
fi
echo "CONFIG_COROUTINE_BACKEND=$coroutine" >> $config_host_mak
+if test "$coroutine_pool" = "yes" ; then
+ echo "CONFIG_COROUTINE_POOL=1" >> $config_host_mak
+else
+ echo "CONFIG_COROUTINE_POOL=0" >> $config_host_mak
+fi
if test "$open_by_handle_at" = "yes" ; then
echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak
