Now that each AioContext has a ThreadPool and the main loop AioContext
can be fetched with bdrv_get_aio_context(), we can eliminate the concept
of a global thread pool from thread-pool.c.
The submit functions must take a ThreadPool* argument.
block/raw-posix.c and block/raw-win32.c use
aio_get_thread_pool(bdrv_get_aio_context(bs)) to fetch the main loop's
ThreadPool.
tests/test-thread-pool.c must be updated to reflect the new
thread_pool_submit() function prototypes.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
ThreadPool is tied to an AioContext through its event notifier, which
dictates in which AioContext the work item's callback function will be
invoked.
In order to support multiple AioContexts we need to support multiple
ThreadPool instances.
This patch adds the new/free functions. The free function deserves
special attention because it quiesces remaining worker threads. This
requires a new condition variable and a "stopping" flag to let workers
know they should terminate once idle.
We never needed to do this before since the global threadpool was not
explicitly destroyed until process termination.
Also stash the AioContext pointer in ThreadPool so that we can call
aio_set_event_notifier() in thread_pool_free(). We didn't need to hold
onto AioContext previously since there was no free function.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Move global variables into a struct so multiple thread pools can be
supported in the future.
This patch does not change thread-pool.h interfaces. There is still a
global thread pool and it is not yet possible to create/destroy
individual thread pools. Moving the variables into a struct first makes
later patches easier to review.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Now that AIOPool no longer keeps a freelist, it isn't really a "pool"
anymore. Rename it to AIOCBInfo and make it const since it no longer
needs to be modified.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The ordering is:
worker thread consumer thread
-------------------------------------------------------------------
write ret event_notifier_test_and_clear
wmb() read state
write state rmb()
event_notifier_set read ret
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a generic thread-pool. The code is roughly based on posix-aio-compat.c,
with some changes, especially the following:
- use QemuSemaphore instead of QemuCond;
- separate the state of the thread from the return code of the worker
function. The return code is totally opaque for the thread pool;
- do not busy wait when doing cancellation.
A more generic threadpool (but still specific to I/O so that in the future
it can use special scheduling classes or PI mutexes) can have many uses:
it allows more flexibility in raw-posix.c and can more easily be extended
to Win32, and it will also be used to do an msync of the persistent bitmap.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
