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cygserver: raise number of worker threads on demand 

The number of threads in the worker pool is fixed so far.  This is a
problem in XSI IPC scenarions with an unknown number of consumers.
It doesn't make sense to make the pool very big for a start, but when
the need arises, we need to make sure we can serve the request even if
all other worker threads are in a wait state.

This patch changes threaded_queue to just add another worker thread
if all current workers are busy.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2017-03-24 16:18:26 +01:00
parent 838eaf6674
commit 0b73dba4de
2 changed files with 11 additions and 12 deletions
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22
winsup/cygserver/threaded_queue.cc
View File

@ -32,6 +32,7 @@ queue_request::~queue_request ()
threaded_queue::threaded_queue (const size_t initial_workers)
: _workers_count (0),
_workers_busy (0),
_running (false),
_submitters_head (NULL),
_requests_count (0),
@ -161,12 +162,6 @@ threaded_queue::add (queue_request *const therequest)
assert (therequest);
assert (!therequest->_next);
if (!_workers_count)
{
system_printf ("warning: no worker threads to handle request!");
// FIXME: And then what?
}
EnterCriticalSection (&_queue_lock);
if (!_requests_head)
_requests_head = therequest;
@ -186,6 +181,12 @@ threaded_queue::add (queue_request *const therequest)
LeaveCriticalSection (&_queue_lock);
(void) ReleaseSemaphore (_requests_sem, 1, NULL);
if (_workers_busy >= _workers_count)
{
create_workers (1);
system_printf ("All threads busy, added one (now %u)", _workers_count);
}
}
/*static*/ DWORD WINAPI
@ -205,17 +206,12 @@ threaded_queue::start_routine (const LPVOID lpParam)
return 0;
}
/* Called from the constructor: so no need to be thread-safe until the
* worker threads start to be created; thus the interlocked increment
* of the `_workers_count' field.
*/
void
threaded_queue::create_workers (const size_t initial_workers)
{
assert (initial_workers > 0);
for (unsigned int i = 0; i != initial_workers; i++)
for (unsigned int i = 0; i < initial_workers; i++)
{
const long count = InterlockedIncrement (&_workers_count);
assert (count > 0);
@ -265,7 +261,9 @@ threaded_queue::worker_loop ()
LeaveCriticalSection (&_queue_lock);
assert (reqptr);
InterlockedIncrement (&_workers_busy);
reqptr->process ();
InterlockedDecrement (&_workers_busy);
delete reqptr;
}
}

1
winsup/cygserver/threaded_queue.h
View File

@ -49,6 +49,7 @@ public:
private:
LONG _workers_count;
LONG _workers_busy;
bool _running;
queue_submission_loop *_submitters_head;