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Changeset: e79b2edeba71 for MonetDB URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=e79b2edeba71 Modified Files: monetdb5/mal/mal.c monetdb5/mal/mal.h monetdb5/mal/mal_interpreter.c Branch: Feb2013 Log Message:

Limit the number of concurrent queries The total throughput for small (and large) queries is improved if we limit the number of concurrent queries being executed. This patch is geared at SQL, wrapping callMAL with a semaphore to limit the level of parallelism to number of physical cores.

diffs (59 lines):

diff --git a/monetdb5/mal/mal.c b/monetdb5/mal/mal.c --- a/monetdb5/mal/mal.c +++ b/monetdb5/mal/mal.c @@ -195,6 +195,7 @@ MT_Lock mal_remoteLock; MT_Lock mal_profileLock ; MT_Lock mal_copyLock; MT_Lock mal_delayLock; +MT_Sema mal_parallelism; /*

• Initialization of the MAL context
• The compiler directive STRUCT_ALIGNED tells that the

@@ -233,6 +234,7 @@ int mal_init(void){ MT_lock_init( &mal_profileLock, "mal_profileLock"); MT_lock_init( &mal_copyLock, "mal_copyLock"); MT_lock_init( &mal_delayLock, "mal_delayLock");

• MT_sema_init( &mal_parallelism, (GDKnr_threads ? GDKnr_threads/2 : 4), "mal_parallelism");

                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

With GDKnr_threads == 1 (single threaded execution or single-core system), this results in mal_parallelism == 0, which in turn results in all SQL tests failing (hanging until timeout) with `Mtest.py -n1` (single-threaded).

Maybe you intended one of (I cannot guess which one):

MT_sema_init( &mal_parallelism, (GDKnr_threads > 8 ? GDKnr_threads/2 : 4), "mal_parallelism");

MT_sema_init( &mal_parallelism, (GDKnr_threads > 4 ? GDKnr_threads/2 : 2), "mal_parallelism");

MT_sema_init( &mal_parallelism, (GDKnr_threads > 2 ? GDKnr_threads/2 : 1), "mal_parallelism");

Stefan

Stefan

...

tstAligned(); MCinit(); diff --git a/monetdb5/mal/mal.h b/monetdb5/mal/mal.h --- a/monetdb5/mal/mal.h +++ b/monetdb5/mal/mal.h @@ -118,6 +118,7 @@ mal_export MT_Lock mal_remoteLock; mal_export MT_Lock mal_profileLock ; mal_export MT_Lock mal_copyLock ; mal_export MT_Lock mal_delayLock ; +mal_export MT_Sema mal_parallelism;

mal_export int mal_init(void); diff --git a/monetdb5/mal/mal_interpreter.c b/monetdb5/mal/mal_interpreter.c --- a/monetdb5/mal/mal_interpreter.c +++ b/monetdb5/mal/mal_interpreter.c @@ -479,7 +479,13 @@ callMAL(Client cntxt, MalBlkPtr mb, MalS ValPtr lhs; InstrPtr pci = getInstrPtr(mb, 0); RuntimeProfileRecord runtimeProfile;

+/*

• • Control the level of parallelism. The maximum number of

concurrent MAL plans

• • is determined by an environment variable. It is initially set

equal to the

• • number of cores, which may be too coarse.
• */
• MT_sema_down(&mal_parallelism,"mal_parallelism"); runtimeProfileInit(mb, &runtimeProfile, cntxt->flags & memoryFlag);

#ifdef DEBUG_CALLMAL mnstr_printf(cntxt->fdout, "callMAL\n"); @@ -518,8 +524,10 @@ callMAL(Client cntxt, MalBlkPtr mb, MalS case PATcall: case CMDcall: default:

• MT_sema_up(&mal_parallelism,"mal_parallelism");
  

  throw(MAL, "mal.interpreter", RUNTIME_UNKNOWN_INSTRUCTION); }
• MT_sema_up(&mal_parallelism,"mal_parallelism"); if (cntxt->qtimeout && time(NULL) - stk->clock.tv_usec > cntxt->qtimeout) throw(MAL, "mal.interpreter", RUNTIME_QRY_TIMEOUT); return ret;

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