src/cpu/sparc/vm/vm_version_sparc.cpp

Fri, 17 Mar 2017 03:39:23 -0700

author
kevinw
date
Fri, 17 Mar 2017 03:39:23 -0700
changeset 8966
c0f6c987718c
parent 8944
072770c9a6b9
child 8967
305c7da1388b
permissions
-rw-r--r--

8049717: expose L1_data_cache_line_size for diagnostic/sanity checks
Summary: Add support for VM_Version::L1_data_cache_line_size().
Reviewed-by: dsimms, kvn, dholmes

     1 /*
     2  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
     4  *
     5  * This code is free software; you can redistribute it and/or modify it
     6  * under the terms of the GNU General Public License version 2 only, as
     7  * published by the Free Software Foundation.
     8  *
     9  * This code is distributed in the hope that it will be useful, but WITHOUT
    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    12  * version 2 for more details (a copy is included in the LICENSE file that
    13  * accompanied this code).
    14  *
    15  * You should have received a copy of the GNU General Public License version
    16  * 2 along with this work; if not, write to the Free Software Foundation,
    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    18  *
    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
    20  * or visit www.oracle.com if you need additional information or have any
    21  * questions.
    22  *
    23  */
    25 #include "precompiled.hpp"
    26 #include "asm/macroAssembler.inline.hpp"
    27 #include "memory/resourceArea.hpp"
    28 #include "runtime/java.hpp"
    29 #include "runtime/stubCodeGenerator.hpp"
    30 #include "vm_version_sparc.hpp"
    31 #ifdef TARGET_OS_FAMILY_linux
    32 # include "os_linux.inline.hpp"
    33 #endif
    34 #ifdef TARGET_OS_FAMILY_solaris
    35 # include "os_solaris.inline.hpp"
    36 #endif
    38 int VM_Version::_features = VM_Version::unknown_m;
    39 const char* VM_Version::_features_str = "";
    40 unsigned int VM_Version::_L2_data_cache_line_size = 0;
    42 void VM_Version::initialize() {
    44   assert(_features != VM_Version::unknown_m, "System pre-initialization is not complete.");
    45   guarantee(VM_Version::has_v9(), "only SPARC v9 is supported");
    47   PrefetchCopyIntervalInBytes = prefetch_copy_interval_in_bytes();
    48   PrefetchScanIntervalInBytes = prefetch_scan_interval_in_bytes();
    49   PrefetchFieldsAhead         = prefetch_fields_ahead();
    51   assert(0 <= AllocatePrefetchInstr && AllocatePrefetchInstr <= 1, "invalid value");
    52   if( AllocatePrefetchInstr < 0 ) AllocatePrefetchInstr = 0;
    53   if( AllocatePrefetchInstr > 1 ) AllocatePrefetchInstr = 0;
    55   // Allocation prefetch settings
    56   intx cache_line_size = prefetch_data_size();
    57   if( cache_line_size > AllocatePrefetchStepSize )
    58     AllocatePrefetchStepSize = cache_line_size;
    60   assert(AllocatePrefetchLines > 0, "invalid value");
    61   if( AllocatePrefetchLines < 1 )     // set valid value in product VM
    62     AllocatePrefetchLines = 3;
    63   assert(AllocateInstancePrefetchLines > 0, "invalid value");
    64   if( AllocateInstancePrefetchLines < 1 ) // set valid value in product VM
    65     AllocateInstancePrefetchLines = 1;
    67   AllocatePrefetchDistance = allocate_prefetch_distance();
    68   AllocatePrefetchStyle    = allocate_prefetch_style();
    70   assert((AllocatePrefetchDistance % AllocatePrefetchStepSize) == 0 &&
    71          (AllocatePrefetchDistance > 0), "invalid value");
    72   if ((AllocatePrefetchDistance % AllocatePrefetchStepSize) != 0 ||
    73       (AllocatePrefetchDistance <= 0)) {
    74     AllocatePrefetchDistance = AllocatePrefetchStepSize;
    75   }
    77   if (AllocatePrefetchStyle == 3 && (!has_blk_init() || cache_line_size <= 0)) {
    78     warning("BIS instructions are not available on this CPU");
    79     FLAG_SET_DEFAULT(AllocatePrefetchStyle, 1);
    80   }
    82   assert(ArraycopySrcPrefetchDistance < 4096, "invalid value");
    83   if (ArraycopySrcPrefetchDistance >= 4096)
    84     ArraycopySrcPrefetchDistance = 4064;
    85   assert(ArraycopyDstPrefetchDistance < 4096, "invalid value");
    86   if (ArraycopyDstPrefetchDistance >= 4096)
    87     ArraycopyDstPrefetchDistance = 4064;
    89   UseSSE = 0; // Only on x86 and x64
    91   _supports_cx8 = has_v9();
    92   _supports_atomic_getset4 = true; // swap instruction
    94   // There are Fujitsu Sparc64 CPUs which support blk_init as well so
    95   // we have to take this check out of the 'is_niagara()' block below.
    96   if (has_blk_init()) {
    97     // When using CMS or G1, we cannot use memset() in BOT updates
    98     // because the sun4v/CMT version in libc_psr uses BIS which
    99     // exposes "phantom zeros" to concurrent readers. See 6948537.
   100     if (FLAG_IS_DEFAULT(UseMemSetInBOT) && (UseConcMarkSweepGC || UseG1GC)) {
   101       FLAG_SET_DEFAULT(UseMemSetInBOT, false);
   102     }
   103     // Issue a stern warning if the user has explicitly set
   104     // UseMemSetInBOT (it is known to cause issues), but allow
   105     // use for experimentation and debugging.
   106     if (UseConcMarkSweepGC || UseG1GC) {
   107       if (UseMemSetInBOT) {
   108         assert(!FLAG_IS_DEFAULT(UseMemSetInBOT), "Error");
   109         warning("Experimental flag -XX:+UseMemSetInBOT is known to cause instability"
   110                 " on sun4v; please understand that you are using at your own risk!");
   111       }
   112     }
   113   }
   115   if (is_niagara()) {
   116     // Indirect branch is the same cost as direct
   117     if (FLAG_IS_DEFAULT(UseInlineCaches)) {
   118       FLAG_SET_DEFAULT(UseInlineCaches, false);
   119     }
   120     // Align loops on a single instruction boundary.
   121     if (FLAG_IS_DEFAULT(OptoLoopAlignment)) {
   122       FLAG_SET_DEFAULT(OptoLoopAlignment, 4);
   123     }
   124 #ifdef _LP64
   125     // 32-bit oops don't make sense for the 64-bit VM on sparc
   126     // since the 32-bit VM has the same registers and smaller objects.
   127     Universe::set_narrow_oop_shift(LogMinObjAlignmentInBytes);
   128     Universe::set_narrow_klass_shift(LogKlassAlignmentInBytes);
   129 #endif // _LP64
   130 #ifdef COMPILER2
   131     // Indirect branch is the same cost as direct
   132     if (FLAG_IS_DEFAULT(UseJumpTables)) {
   133       FLAG_SET_DEFAULT(UseJumpTables, true);
   134     }
   135     // Single-issue, so entry and loop tops are
   136     // aligned on a single instruction boundary
   137     if (FLAG_IS_DEFAULT(InteriorEntryAlignment)) {
   138       FLAG_SET_DEFAULT(InteriorEntryAlignment, 4);
   139     }
   140     if (is_niagara_plus()) {
   141       if (has_blk_init() && (cache_line_size > 0) && UseTLAB &&
   142           FLAG_IS_DEFAULT(AllocatePrefetchInstr)) {
   143         // Use BIS instruction for TLAB allocation prefetch.
   144         FLAG_SET_ERGO(intx, AllocatePrefetchInstr, 1);
   145         if (FLAG_IS_DEFAULT(AllocatePrefetchStyle)) {
   146           FLAG_SET_ERGO(intx, AllocatePrefetchStyle, 3);
   147         }
   148         if (FLAG_IS_DEFAULT(AllocatePrefetchDistance)) {
   149           // Use smaller prefetch distance with BIS
   150           FLAG_SET_DEFAULT(AllocatePrefetchDistance, 64);
   151         }
   152       }
   153       if (is_T4()) {
   154         // Double number of prefetched cache lines on T4
   155         // since L2 cache line size is smaller (32 bytes).
   156         if (FLAG_IS_DEFAULT(AllocatePrefetchLines)) {
   157           FLAG_SET_ERGO(intx, AllocatePrefetchLines, AllocatePrefetchLines*2);
   158         }
   159         if (FLAG_IS_DEFAULT(AllocateInstancePrefetchLines)) {
   160           FLAG_SET_ERGO(intx, AllocateInstancePrefetchLines, AllocateInstancePrefetchLines*2);
   161         }
   162       }
   163       if (AllocatePrefetchStyle != 3 && FLAG_IS_DEFAULT(AllocatePrefetchDistance)) {
   164         // Use different prefetch distance without BIS
   165         FLAG_SET_DEFAULT(AllocatePrefetchDistance, 256);
   166       }
   167       if (AllocatePrefetchInstr == 1) {
   168         // Need a space at the end of TLAB for BIS since it
   169         // will fault when accessing memory outside of heap.
   171         // +1 for rounding up to next cache line, +1 to be safe
   172         int lines = AllocatePrefetchLines + 2;
   173         int step_size = AllocatePrefetchStepSize;
   174         int distance = AllocatePrefetchDistance;
   175         _reserve_for_allocation_prefetch = (distance + step_size*lines)/(int)HeapWordSize;
   176       }
   177     }
   178 #endif
   179   }
   181   // Use hardware population count instruction if available.
   182   if (has_hardware_popc()) {
   183     if (FLAG_IS_DEFAULT(UsePopCountInstruction)) {
   184       FLAG_SET_DEFAULT(UsePopCountInstruction, true);
   185     }
   186   } else if (UsePopCountInstruction) {
   187     warning("POPC instruction is not available on this CPU");
   188     FLAG_SET_DEFAULT(UsePopCountInstruction, false);
   189   }
   191   // T4 and newer Sparc cpus have new compare and branch instruction.
   192   if (has_cbcond()) {
   193     if (FLAG_IS_DEFAULT(UseCBCond)) {
   194       FLAG_SET_DEFAULT(UseCBCond, true);
   195     }
   196   } else if (UseCBCond) {
   197     warning("CBCOND instruction is not available on this CPU");
   198     FLAG_SET_DEFAULT(UseCBCond, false);
   199   }
   201   assert(BlockZeroingLowLimit > 0, "invalid value");
   202   if (has_block_zeroing() && cache_line_size > 0) {
   203     if (FLAG_IS_DEFAULT(UseBlockZeroing)) {
   204       FLAG_SET_DEFAULT(UseBlockZeroing, true);
   205     }
   206   } else if (UseBlockZeroing) {
   207     warning("BIS zeroing instructions are not available on this CPU");
   208     FLAG_SET_DEFAULT(UseBlockZeroing, false);
   209   }
   211   assert(BlockCopyLowLimit > 0, "invalid value");
   212   if (has_block_zeroing() && cache_line_size > 0) { // has_blk_init() && is_T4(): core's local L2 cache
   213     if (FLAG_IS_DEFAULT(UseBlockCopy)) {
   214       FLAG_SET_DEFAULT(UseBlockCopy, true);
   215     }
   216   } else if (UseBlockCopy) {
   217     warning("BIS instructions are not available or expensive on this CPU");
   218     FLAG_SET_DEFAULT(UseBlockCopy, false);
   219   }
   221 #ifdef COMPILER2
   222   // T4 and newer Sparc cpus have fast RDPC.
   223   if (has_fast_rdpc() && FLAG_IS_DEFAULT(UseRDPCForConstantTableBase)) {
   224     FLAG_SET_DEFAULT(UseRDPCForConstantTableBase, true);
   225   }
   227   // Currently not supported anywhere.
   228   FLAG_SET_DEFAULT(UseFPUForSpilling, false);
   230   MaxVectorSize = 8;
   232   assert((InteriorEntryAlignment % relocInfo::addr_unit()) == 0, "alignment is not a multiple of NOP size");
   233 #endif
   235   assert((CodeEntryAlignment % relocInfo::addr_unit()) == 0, "alignment is not a multiple of NOP size");
   236   assert((OptoLoopAlignment % relocInfo::addr_unit()) == 0, "alignment is not a multiple of NOP size");
   238   char buf[512];
   239   jio_snprintf(buf, sizeof(buf), "%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
   240                (has_v9() ? ", v9" : (has_v8() ? ", v8" : "")),
   241                (has_hardware_popc() ? ", popc" : ""),
   242                (has_vis1() ? ", vis1" : ""),
   243                (has_vis2() ? ", vis2" : ""),
   244                (has_vis3() ? ", vis3" : ""),
   245                (has_blk_init() ? ", blk_init" : ""),
   246                (has_cbcond() ? ", cbcond" : ""),
   247                (has_aes() ? ", aes" : ""),
   248                (has_sha1() ? ", sha1" : ""),
   249                (has_sha256() ? ", sha256" : ""),
   250                (has_sha512() ? ", sha512" : ""),
   251                (is_ultra3() ? ", ultra3" : ""),
   252                (is_sun4v() ? ", sun4v" : ""),
   253                (is_niagara_plus() ? ", niagara_plus" : (is_niagara() ? ", niagara" : "")),
   254                (is_sparc64() ? ", sparc64" : ""),
   255                (!has_hardware_mul32() ? ", no-mul32" : ""),
   256                (!has_hardware_div32() ? ", no-div32" : ""),
   257                (!has_hardware_fsmuld() ? ", no-fsmuld" : ""));
   259   // buf is started with ", " or is empty
   260   _features_str = strdup(strlen(buf) > 2 ? buf + 2 : buf);
   262   // There are three 64-bit SPARC families that do not overlap, e.g.,
   263   // both is_ultra3() and is_sparc64() cannot be true at the same time.
   264   // Within these families, there can be more than one chip, e.g.,
   265   // is_T4() and is_T7() machines are also is_niagara().
   266   if (is_ultra3()) {
   267     assert(_L1_data_cache_line_size == 0, "overlap with Ultra3 family");
   268     // Ref: UltraSPARC III Cu Processor
   269     _L1_data_cache_line_size = 64;
   270   }
   271   if (is_niagara()) {
   272     assert(_L1_data_cache_line_size == 0, "overlap with niagara family");
   273     // All Niagara's are sun4v's, but not all sun4v's are Niagaras, e.g.,
   274     // Fujitsu SPARC64 is sun4v, but we don't want it in this block.
   275     //
   276     // Ref: UltraSPARC T1 Supplement to the UltraSPARC Architecture 2005
   277     // Appendix F.1.3.1 Cacheable Accesses
   278     // -> 16-byte L1 cache line size
   279     //
   280     // Ref: UltraSPARC T2: A Highly-Threaded, Power-Efficient, SPARC SOC
   281     // Section III: SPARC Processor Core
   282     // -> 16-byte L1 cache line size
   283     //
   284     // Ref: Oracle's SPARC T4-1, SPARC T4-2, SPARC T4-4, and SPARC T4-1B Server Architecture
   285     // Section SPARC T4 Processor Cache Architecture
   286     // -> 32-byte L1 cache line size (no longer see that info on this ref)
   287     //
   288     // XXX - still need a T7 reference here
   289     //
   290     if (is_T7()) {  // T7 or newer
   291       _L1_data_cache_line_size = 64;
   292     } else if (is_T4()) {  // T4 or newer (until T7)
   293       _L1_data_cache_line_size = 32;
   294     } else {  // T1 or newer (until T4)
   295       _L1_data_cache_line_size = 16;
   296     }
   297   }
   298   if (is_sparc64()) {
   299     guarantee(_L1_data_cache_line_size == 0, "overlap with SPARC64 family");
   300     // Ref: Fujitsu SPARC64 VII Processor
   301     // Section 4 Cache System
   302     _L1_data_cache_line_size = 64;
   303   }
   305   // UseVIS is set to the smallest of what hardware supports and what
   306   // the command line requires.  I.e., you cannot set UseVIS to 3 on
   307   // older UltraSparc which do not support it.
   308   if (UseVIS > 3) UseVIS=3;
   309   if (UseVIS < 0) UseVIS=0;
   310   if (!has_vis3()) // Drop to 2 if no VIS3 support
   311     UseVIS = MIN2((intx)2,UseVIS);
   312   if (!has_vis2()) // Drop to 1 if no VIS2 support
   313     UseVIS = MIN2((intx)1,UseVIS);
   314   if (!has_vis1()) // Drop to 0 if no VIS1 support
   315     UseVIS = 0;
   317   // SPARC T4 and above should have support for AES instructions
   318   if (has_aes()) {
   319     if (UseVIS > 2) { // AES intrinsics use MOVxTOd/MOVdTOx which are VIS3
   320       if (FLAG_IS_DEFAULT(UseAES)) {
   321         FLAG_SET_DEFAULT(UseAES, true);
   322       }
   323       if (FLAG_IS_DEFAULT(UseAESIntrinsics)) {
   324         FLAG_SET_DEFAULT(UseAESIntrinsics, true);
   325       }
   326       // we disable both the AES flags if either of them is disabled on the command line
   327       if (!UseAES || !UseAESIntrinsics) {
   328         FLAG_SET_DEFAULT(UseAES, false);
   329         FLAG_SET_DEFAULT(UseAESIntrinsics, false);
   330       }
   331     } else {
   332         if (UseAES || UseAESIntrinsics) {
   333           warning("SPARC AES intrinsics require VIS3 instruction support. Intrinsics will be disabled.");
   334           if (UseAES) {
   335             FLAG_SET_DEFAULT(UseAES, false);
   336           }
   337           if (UseAESIntrinsics) {
   338             FLAG_SET_DEFAULT(UseAESIntrinsics, false);
   339           }
   340         }
   341     }
   342   } else if (UseAES || UseAESIntrinsics) {
   343     warning("AES instructions are not available on this CPU");
   344     if (UseAES) {
   345       FLAG_SET_DEFAULT(UseAES, false);
   346     }
   347     if (UseAESIntrinsics) {
   348       FLAG_SET_DEFAULT(UseAESIntrinsics, false);
   349     }
   350   }
   352   // SHA1, SHA256, and SHA512 instructions were added to SPARC T-series at different times
   353   if (has_sha1() || has_sha256() || has_sha512()) {
   354     if (UseVIS > 0) { // SHA intrinsics use VIS1 instructions
   355       if (FLAG_IS_DEFAULT(UseSHA)) {
   356         FLAG_SET_DEFAULT(UseSHA, true);
   357       }
   358     } else {
   359       if (UseSHA) {
   360         warning("SPARC SHA intrinsics require VIS1 instruction support. Intrinsics will be disabled.");
   361         FLAG_SET_DEFAULT(UseSHA, false);
   362       }
   363     }
   364   } else if (UseSHA) {
   365     warning("SHA instructions are not available on this CPU");
   366     FLAG_SET_DEFAULT(UseSHA, false);
   367   }
   369   if (!UseSHA) {
   370     FLAG_SET_DEFAULT(UseSHA1Intrinsics, false);
   371     FLAG_SET_DEFAULT(UseSHA256Intrinsics, false);
   372     FLAG_SET_DEFAULT(UseSHA512Intrinsics, false);
   373   } else {
   374     if (has_sha1()) {
   375       if (FLAG_IS_DEFAULT(UseSHA1Intrinsics)) {
   376         FLAG_SET_DEFAULT(UseSHA1Intrinsics, true);
   377       }
   378     } else if (UseSHA1Intrinsics) {
   379       warning("SHA1 instruction is not available on this CPU.");
   380       FLAG_SET_DEFAULT(UseSHA1Intrinsics, false);
   381     }
   382     if (has_sha256()) {
   383       if (FLAG_IS_DEFAULT(UseSHA256Intrinsics)) {
   384         FLAG_SET_DEFAULT(UseSHA256Intrinsics, true);
   385       }
   386     } else if (UseSHA256Intrinsics) {
   387       warning("SHA256 instruction (for SHA-224 and SHA-256) is not available on this CPU.");
   388       FLAG_SET_DEFAULT(UseSHA256Intrinsics, false);
   389     }
   391     if (has_sha512()) {
   392       if (FLAG_IS_DEFAULT(UseSHA512Intrinsics)) {
   393         FLAG_SET_DEFAULT(UseSHA512Intrinsics, true);
   394       }
   395     } else if (UseSHA512Intrinsics) {
   396       warning("SHA512 instruction (for SHA-384 and SHA-512) is not available on this CPU.");
   397       FLAG_SET_DEFAULT(UseSHA512Intrinsics, false);
   398     }
   399     if (!(UseSHA1Intrinsics || UseSHA256Intrinsics || UseSHA512Intrinsics)) {
   400       FLAG_SET_DEFAULT(UseSHA, false);
   401     }
   402   }
   404   if (FLAG_IS_DEFAULT(ContendedPaddingWidth) &&
   405     (cache_line_size > ContendedPaddingWidth))
   406     ContendedPaddingWidth = cache_line_size;
   408 #ifndef PRODUCT
   409   if (PrintMiscellaneous && Verbose) {
   410     tty->print_cr("L1 data cache line size: %u", L1_data_cache_line_size());
   411     tty->print_cr("L2 data cache line size: %u", L2_data_cache_line_size());
   412     tty->print("Allocation");
   413     if (AllocatePrefetchStyle <= 0) {
   414       tty->print_cr(": no prefetching");
   415     } else {
   416       tty->print(" prefetching: ");
   417       if (AllocatePrefetchInstr == 0) {
   418           tty->print("PREFETCH");
   419       } else if (AllocatePrefetchInstr == 1) {
   420           tty->print("BIS");
   421       }
   422       if (AllocatePrefetchLines > 1) {
   423         tty->print_cr(" at distance %d, %d lines of %d bytes", (int) AllocatePrefetchDistance, (int) AllocatePrefetchLines, (int) AllocatePrefetchStepSize);
   424       } else {
   425         tty->print_cr(" at distance %d, one line of %d bytes", (int) AllocatePrefetchDistance, (int) AllocatePrefetchStepSize);
   426       }
   427     }
   428     if (PrefetchCopyIntervalInBytes > 0) {
   429       tty->print_cr("PrefetchCopyIntervalInBytes %d", (int) PrefetchCopyIntervalInBytes);
   430     }
   431     if (PrefetchScanIntervalInBytes > 0) {
   432       tty->print_cr("PrefetchScanIntervalInBytes %d", (int) PrefetchScanIntervalInBytes);
   433     }
   434     if (PrefetchFieldsAhead > 0) {
   435       tty->print_cr("PrefetchFieldsAhead %d", (int) PrefetchFieldsAhead);
   436     }
   437     if (ContendedPaddingWidth > 0) {
   438       tty->print_cr("ContendedPaddingWidth %d", (int) ContendedPaddingWidth);
   439     }
   440   }
   441 #endif // PRODUCT
   442 }
   444 void VM_Version::print_features() {
   445   tty->print_cr("Version:%s", cpu_features());
   446 }
   448 int VM_Version::determine_features() {
   449   if (UseV8InstrsOnly) {
   450     NOT_PRODUCT(if (PrintMiscellaneous && Verbose) tty->print_cr("Version is Forced-V8");)
   451     return generic_v8_m;
   452   }
   454   int features = platform_features(unknown_m); // platform_features() is os_arch specific
   456   if (features == unknown_m) {
   457     features = generic_v9_m;
   458     warning("Cannot recognize SPARC version. Default to V9");
   459   }
   461   assert(is_T_family(features) == is_niagara(features), "Niagara should be T series");
   462   if (UseNiagaraInstrs) { // Force code generation for Niagara
   463     if (is_T_family(features)) {
   464       // Happy to accomodate...
   465     } else {
   466       NOT_PRODUCT(if (PrintMiscellaneous && Verbose) tty->print_cr("Version is Forced-Niagara");)
   467       features |= T_family_m;
   468     }
   469   } else {
   470     if (is_T_family(features) && !FLAG_IS_DEFAULT(UseNiagaraInstrs)) {
   471       NOT_PRODUCT(if (PrintMiscellaneous && Verbose) tty->print_cr("Version is Forced-Not-Niagara");)
   472       features &= ~(T_family_m | T1_model_m);
   473     } else {
   474       // Happy to accomodate...
   475     }
   476   }
   478   return features;
   479 }
   481 static int saved_features = 0;
   483 void VM_Version::allow_all() {
   484   saved_features = _features;
   485   _features      = all_features_m;
   486 }
   488 void VM_Version::revert() {
   489   _features = saved_features;
   490 }
   492 unsigned int VM_Version::calc_parallel_worker_threads() {
   493   unsigned int result;
   494   if (is_M_series()) {
   495     // for now, use same gc thread calculation for M-series as for niagara-plus
   496     // in future, we may want to tweak parameters for nof_parallel_worker_thread
   497     result = nof_parallel_worker_threads(5, 16, 8);
   498   } else if (is_niagara_plus()) {
   499     result = nof_parallel_worker_threads(5, 16, 8);
   500   } else {
   501     result = nof_parallel_worker_threads(5, 8, 8);
   502   }
   503   return result;
   504 }

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