[Xen-changelog] [qemu-upstream-unstable] coroutine: add ./configure --disable-coroutine-pool

[patchbot@xxxxxxx]

commit ba20326a937421c50a775907dc9ac726bb9a9b50
Author:     Stefan Hajnoczi <stefanha@xxxxxxxxxx>
AuthorDate: Wed Sep 11 16:42:35 2013 +0200
Commit:     Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon Sep 30 22:57:15 2013 -0500

    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@xxxxxxxxxxxx>
    Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    Reviewed-by: Gabriel Kerneis <gabriel@xxxxxxxxxxxx>
    Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
    (cherry picked from commit 70c60c089fdc6bf8a79324e492c13e8c08d55942)
    
    Signed-off-by: Michael Roth <mdroth@xxxxxxxxxxxxxxxxxx>
---
 configure        |   24 ++++++++++++++++++++++++
 qemu-coroutine.c |   32 ++++++++++++++++++--------------
 2 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/configure b/configure
index 18fa608..4cf672d 100755
--- a/configure
+++ b/configure
@@ -235,6 +235,7 @@ guest_agent=""
 want_tools="yes"
 libiscsi=""
 coroutine=""
+coroutine_pool=""
 seccomp=""
 glusterfs=""
 glusterfs_discard="no"
@@ -871,6 +872,10 @@ 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"
@@ -1152,6 +1157,8 @@ 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"
@@ -3240,6 +3247,17 @@ 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
 
@@ -3605,6 +3623,7 @@ 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              $gcov_tool"
@@ -3954,6 +3973,11 @@ if test "$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
 
 if test "$open_by_handle_at" = "yes" ; then
   echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak
diff --git a/qemu-coroutine.c b/qemu-coroutine.c
index 423430d..4708521 100644
--- a/qemu-coroutine.c
+++ b/qemu-coroutine.c
@@ -30,15 +30,17 @@ static unsigned int pool_size;
 
 Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
 {
-    Coroutine *co;
-
-    qemu_mutex_lock(&pool_lock);
-    co = QSLIST_FIRST(&pool);
-    if (co) {
-        QSLIST_REMOVE_HEAD(&pool, pool_next);
-        pool_size--;
+    Coroutine *co = NULL;
+
+    if (CONFIG_COROUTINE_POOL) {
+        qemu_mutex_lock(&pool_lock);
+        co = QSLIST_FIRST(&pool);
+        if (co) {
+            QSLIST_REMOVE_HEAD(&pool, pool_next);
+            pool_size--;
+        }
+        qemu_mutex_unlock(&pool_lock);
     }
-    qemu_mutex_unlock(&pool_lock);
 
     if (!co) {
         co = qemu_coroutine_new();
@@ -51,15 +53,17 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
 
 static void coroutine_delete(Coroutine *co)
 {
-    qemu_mutex_lock(&pool_lock);
-    if (pool_size < POOL_MAX_SIZE) {
-        QSLIST_INSERT_HEAD(&pool, co, pool_next);
-        co->caller = NULL;
-        pool_size++;
+    if (CONFIG_COROUTINE_POOL) {
+        qemu_mutex_lock(&pool_lock);
+        if (pool_size < POOL_MAX_SIZE) {
+            QSLIST_INSERT_HEAD(&pool, co, pool_next);
+            co->caller = NULL;
+            pool_size++;
+            qemu_mutex_unlock(&pool_lock);
+            return;
+        }
         qemu_mutex_unlock(&pool_lock);
-        return;
     }
-    qemu_mutex_unlock(&pool_lock);
 
     qemu_coroutine_delete(co);
 }
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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