Am 11.09.2013 um 16:42 hat Stefan Hajnoczi geschrieben:
> 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 <gabr...@kerneis.info>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> configure | 24 ++++++++++++++++++++++++
> qemu-coroutine.c | 34 +++++++++++++++++++---------------
> 2 files changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/configure b/configure
> index e989609..5cf6341 100755
> --- a/configure
> +++ b/configure
> @@ -235,6 +235,7 @@ guest_agent=""
> want_tools="yes"
> libiscsi=""
> coroutine=""
> +coroutine_pool=""
> seccomp=""
> glusterfs=""
> glusterfs_discard="no"
> @@ -875,6 +876,10 @@ for opt do
> ;;
> --with-coroutine=*) coroutine="$optarg"
> ;;
> + --disable-coroutine-pool) coroutine_pool="no"
> + ;;
> + --enable-coroutine-pool) coroutine_pool="yes"
> + ;;
> --disable-docs) docs="no"
> ;;
> --enable-docs) docs="yes"
> @@ -1161,6 +1166,8 @@ echo " --disable-seccomp disable seccomp
> support"
> echo " --enable-seccomp enables seccomp support"
> echo " --with-coroutine=BACKEND coroutine backend. Supported options:"
> echo " gthread, ucontext, sigaltstack, windows"
> +echo " --disable-coroutine-pool disable coroutine freelist (worse
> performance)"
> +echo " --enable-coroutine-pool enable coroutine freelist (better
> performance)"
> echo " --enable-glusterfs enable GlusterFS backend"
> echo " --disable-glusterfs disable GlusterFS backend"
> echo " --enable-gcov enable test coverage analysis with gcov"
> @@ -3279,6 +3286,17 @@ else
> esac
> fi
>
> +if test "$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
>
> @@ -3644,6 +3662,7 @@ echo "libiscsi support $libiscsi"
> echo "build guest agent $guest_agent"
> 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 $gcov_tool"
> @@ -3999,6 +4018,11 @@ if test "$rbd" = "yes" ; then
> 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
Doesn't work.
In config-host.make we do get:
CONFIG_COROUTINE_POOL=0
But when config-host.h is generated from it, I assume it's only checked
if the variable is defined, so we end up with:
#define CONFIG_COROUTINE_POOL 1
That is, you never really disable the pool.
Kevin
