On Mon, Dec 5, 2011 at 5:20 PM, Avi Kivity <a...@redhat.com> wrote: > ucontext-based coroutines use a free pool to reduce allocations and > deallocations of coroutine objects. The pool is per-thread, presumably > to improve locality. However, as coroutines are usually allocated in > a vcpu thread and freed in the I/O thread, the pool accounting gets > screwed up and we end allocating and freeing a coroutine for every I/O > request. This is expensive since large objects are allocated via the > kernel, and are not cached by the C runtime. > > Fix by switching to a global pool. This is safe since we're protected > by the global mutex.
Looks good to me. I did check how hw/9pfs/ uses coroutines because it bounces them into worker threads that are not under the QEMU mutex but they are not created/destroyed there so we should be okay. Stefan
