bk commit into 5.1 tree (knielsen:1.2614)

[knielsen]

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ChangeSet@stripped, 2007-11-01 11:30:33+01:00, knielsen@ymer.(none) +1 -0
  WL#1498: Multi-threaded ndbd
  
  Add some prefetching found with OProfile to decrease cache misses.

  storage/ndb/src/kernel/vm/mt/mt.cpp@stripped, 2007-11-01 11:30:29+01:00, knielsen@ymer.(none) +24 -3
    Add some prefetching found with OProfile to decrease cache misses.

diff -Nrup a/storage/ndb/src/kernel/vm/mt/mt.cpp b/storage/ndb/src/kernel/vm/mt/mt.cpp
--- a/storage/ndb/src/kernel/vm/mt/mt.cpp	2007-10-30 11:34:36 +01:00
+++ b/storage/ndb/src/kernel/vm/mt/mt.cpp	2007-11-01 11:30:29 +01:00
@@ -33,6 +33,7 @@
 #include <sys/syscall.h>
 #include <sys/types.h>
 
+//#define memcpy __builtin_memcpy
 
 /* Constants found by benchmarks to be reasonable values. */
 
@@ -977,11 +978,21 @@ execute_signals(thr_data *selfptr, thr_j
       }
     }
 
+    /*
+     * These pre-fetching were found using OProfile to reduce cache misses.
+     * (Though on Intel Core 2, they do not give much speedup, as apparently
+     * the hardware prefetcher is already doing a fairly good job).
+     */
+    __builtin_prefetch (read_buffer->m_data + read_pos + 16, 0, 3);
+    __builtin_prefetch ((Uint32 *)&sig->header + 16, 1, 3);
+
     /* Now execute the signal. */
     SignalHeader* s =
       reinterpret_cast<SignalHeader*>(&(read_buffer->m_data[read_pos]));
     Uint32 seccnt = s->m_noOfSections;
     Uint32 siglen = (sizeof(*s)>>2) + s->theLength;
+    if(siglen>16)
+      __builtin_prefetch (read_buffer->m_data + read_pos + 32, 0, 3);
     Uint32 bno = s->theReceiversBlockNumber;
     Uint32 gsn = s->theVerId_signalNumber;
     SimulatedBlock * block = blockptr[bno];
@@ -1077,7 +1088,8 @@ extern "C"
 void *
 mt_thr_main(void *thr_arg)
 {
-  Signal signal;
+  unsigned char signal_buf[sizeof(Signal) + 63 + 256 * MAX_THREADS];
+  Signal *signal;
   struct timespec nowait;
   nowait.tv_sec = 0;
   nowait.tv_nsec = 10 * 1000000;
@@ -1100,6 +1112,15 @@ mt_thr_main(void *thr_arg)
     the numeric thread id in this slightly backwards way.
   */
   unsigned thr_no = selfptr - &(rep->m_thread[0]);
+  /*
+   * Align signal buffer for better cache performance.
+   * Also skew it a litte for each thread to avoid cache pollution.
+   */
+  UintPtr sigtmp= (UintPtr)signal_buf;
+  sigtmp= (sigtmp+63) & (~(UintPtr)63);
+  sigtmp+= thr_no*256;
+  signal = (Signal *)sigtmp;
+
   pid_t tid = (unsigned)syscall(SYS_gettid);
   ndbout_c("Tread %u started, tid=%u", thr_no, tid);
 #ifdef NDB_MT_LOCK_TO_CPU
@@ -1139,11 +1160,11 @@ mt_thr_main(void *thr_arg)
     watchDogCounter = 2;
     scan_time_queues(selfptr);
 
-    Uint32 sum = run_job_buffers(selfptr, &signal,
+    Uint32 sum = run_job_buffers(selfptr, signal,
                                  &watchDogCounter, &thrSignalId);
     
     watchDogCounter = 1;
-    sendpacked(selfptr, &signal, thr_no);
+    sendpacked(selfptr, signal, thr_no);
     
     if (sum)
     {