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1 /*
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2 * Copyright 1998-2005 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 public:
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26 // Java Thread - force inlining
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27 static inline Thread* thread() ;
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28
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29 private:
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30 static Thread* _get_thread_cache[]; // index by [(raw_id>>9)^(raw_id>>20) % _pd_cache_size]
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31 static Thread* get_thread_via_cache_slowly(uintptr_t raw_id, int index);
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32
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33 NOT_PRODUCT(static int _tcacheHit;)
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34 NOT_PRODUCT(static int _tcacheMiss;)
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35
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36 public:
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37
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38 // Print cache hit/miss statistics
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39 static void print_statistics() PRODUCT_RETURN;
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40
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41 enum Constants {
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42 _pd_cache_size = 256*2 // projected typical # of threads * 2
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43 };
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44
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45 static void set_thread_in_slot (Thread *) ;
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46
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47 static uintptr_t pd_raw_thread_id() {
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48 return _raw_thread_id();
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49 }
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50
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51 static int pd_cache_index(uintptr_t raw_id) {
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52 // Hash function: From email from Dave:
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53 // The hash function deserves an explanation. %g7 points to libthread's
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54 // "thread" structure. On T1 the thread structure is allocated on the
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55 // user's stack (yes, really!) so the ">>20" handles T1 where the JVM's
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56 // stack size is usually >= 1Mb. The ">>9" is for T2 where Roger allocates
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57 // globs of thread blocks contiguously. The "9" has to do with the
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58 // expected size of the T2 thread structure. If these constants are wrong
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59 // the worst thing that'll happen is that the hit rate for heavily threaded
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60 // apps won't be as good as it could be. If you want to burn another
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61 // shift+xor you could mix together _all of the %g7 bits to form the hash,
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62 // but I think that's excessive. Making the change above changed the
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63 // T$ miss rate on SpecJBB (on a 16X system) from about 3% to imperceptible.
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64 uintptr_t ix = (int) (((raw_id >> 9) ^ (raw_id >> 20)) % _pd_cache_size);
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65 return ix;
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66 }
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