PP now uses PriorityThreadPool that arbitrary picks another jobs pack
to run. This scheduling discipline tend to run portions of a single query
forcing other simultaneous queries to wait. In result parallel queries
timings variance is high. The FairThreadPool picks the job with the smallest
amount of work done so far(see the code for details)
respondWait could be set to false while other threads were waiting. With respondWait false, okToRrespond wouldn't ever get notify_one().
Get rid of respondWait and use fProcessorPool->blockedThreadCount to determine if any threads may be waiting.
* MCOL-4846 dev-6 Handle large join results
Use a loop to shrink the number of results reported per message to something manageable.
* MCOL-4841 small changes requested by review
* Add EXTRA threads to prioritythreadpool
prioritythreadpool is configured at startup with a fixed number of threads available. This is to prevent thread thrashing. Since most of the time, BPP job steps are short lived, and a rescheduling mechanism exist if no threads are available, this works to keep cpu wastage to a minimum.
However, if a query or queries consume all the threads in prioritythreadpool and then block (due to the consumer not consuming fast enough) we can run out of threads and no work will be done until some threads unblock. A new mechanism allows for EXTRA threads to be generated for the duration of the blocking action. These threads can act on new queries. When all blocking is completed, these threads will be released when idle.
* MCOL-4841 dev6 Reconcile with changes in develop-6
* MCOL-4841 Some format corrections
* MCOL-4841 dev clean up some things based on review
* MCOL-4841 dev 6 ExeMgr Crashes after large join
This commit fixes up memory accounting issues in ExeMgr
* MCOL-4841 remove LDI change
Opened MCOL-4968 to address the issue
* MCOL-4841 Add fMaxBPPSendQueue to ResourceManager
This causes the setting to be loaded at run time (requires restart to accept a change) BPPSendthread gets this in it's ctor
Also rolled back changes to TupleHashJoinStep::smallRunnerFcn() that used a local variable to count locally allocated memory, then added it into the global counter at function's end. Not counting the memory globally caused conversion to UM only join way later than it should. This resulted in MCOL-4971.
* MCOL-4841 make blockedThreads and extraThreads atomic
Also restore previous scope of locks in bppsendthread. There is some small chance the new scope could be incorrect, and the performance boost is negligible. Better safe than sorry.
PriorityThreadPool didn't have very good error handling. If something
failed it would just ignore whatever was being processed. This could
lead to a query continuing without retreiving all of the required data.
This patch adds error handling, sending a message back to the client
and a log message. It also destroys and recreates the pool thread.
