qemu/AIO-Reduce-number-of-threads-for-32bit-h.patch

From: Alexander Graf <agraf@suse.de>
Date: Wed, 14 Jan 2015 01:32:11 +0100
Subject: AIO: Reduce number of threads for 32bit hosts

On hosts with limited virtual address space (32bit pointers), we can very
easily run out of virtual memory with big thread pools.

Instead, we should limit ourselves to small pools to keep memory footprint
low on those systems.

This patch fixes random VM stalls like

  (process:25114): GLib-ERROR **: gmem.c:103: failed to allocate 1048576 bytes

on 32bit ARM systems for me.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 util/thread-pool.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/util/thread-pool.c b/util/thread-pool.c
index d763cea505b68575af8e1b39cd95..785487b8767d96ca76c643f1851f 100644
--- a/util/thread-pool.c
+++ b/util/thread-pool.c
@@ -306,7 +306,12 @@ static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
     qemu_mutex_init(&pool->lock);
     qemu_cond_init(&pool->worker_stopped);
     qemu_sem_init(&pool->sem, 0);
-    pool->max_threads = 64;
+    if (sizeof(pool) == 4) {
+        /* 32bit systems run out of virtual memory quickly */
+        pool->max_threads = 4;
+    } else {
+        pool->max_threads = 64;
+    }
     pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);
 
     QLIST_INIT(&pool->head);