Bug ID: JDK-6806090 please implement AlwaysPreTouch option for jse 1.5.0

Type: Bug
Component: hotspot
Sub-Component: gc
Affected Version: 5.0u17

Priority: P2
Status: Closed
Resolution: Fixed
OS: solaris
CPU: sparc

Submitted: 2009-02-16
Updated: 2010-08-18
Resolved: 2009-12-30

Other
5.0u23 b01Fixed

implementing AlwaysPreTouch is needed for University of Toronto to see
the improvement in CMS/ParNew times (variance) they are interested in.

   SEE Suggested Fix for changes made.

EVALUATION This c/r is being worked as part of esc 1-25424928 [ c/r 6786503 ].

04-03-2009

SUGGESTED FIX *** src/share/vm/runtime/globals.hpp- Thu Nov 20 01:14:16 2008 --- src/share/vm/runtime/globals.hpp Tue Feb 17 10:42:44 2009 *************** *** 1,12 **** #ifdef USE_PRAGMA_IDENT_HDR ! #pragma ident "@(#)globals.hpp 1.856 08/04/22 11:10:51 JVM" #endif /* ! * @(#)globals.hpp 1.856 08/04/22 * ! * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ typedef const char* ccstr; // string type alias used only in this file --- 1,12 ---- #ifdef USE_PRAGMA_IDENT_HDR ! #pragma ident "%W% %E% %U% JVM" #endif /* ! * %W% %E% * ! * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ typedef const char* ccstr; // string type alias used only in this file *************** *** 1023,1032 **** --- 1023,1035 ---- \ product(intx, ParCMSPromoteBlocksToClaim, 50, \ "Number of blocks to attempt to claim when refilling CMS LAB for "\ "parallel GC.") \ \ + product(bool, AlwaysPreTouch, false, \ + "It forces all freshly committed pages to be pre-touched.") \ + \ product(bool, CMSIncrementalMode, false, \ "Whether CMS GC should operate in \"incremental\" mode") \ \ product(uintx, CMSIncrementalDutyCycle, 50, \ "CMS incremental mode duty cycle (a percentage, 0-100). If" \ *** src/share/vm/runtime/virtualspace.cpp- Thu Nov 20 01:14:16 2008 --- src/share/vm/runtime/virtualspace.cpp Tue Feb 17 10:43:42 2009 *************** *** 1,12 **** #ifdef USE_PRAGMA_IDENT_SRC ! #pragma ident "@(#)virtualspace.cpp 1.55 05/08/04 15:43:29 JVM" #endif /* ! * @(#)virtualspace.cpp 1.55 05/08/04 * ! * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ #include "incls/_precompiled.incl" #include "incls/_virtualspace.cpp.incl" --- 1,12 ---- #ifdef USE_PRAGMA_IDENT_SRC ! #pragma ident "%W% %E% %U% JVM" #endif /* ! * %W% %E% * ! * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ #include "incls/_precompiled.incl" #include "incls/_virtualspace.cpp.incl" *************** *** 307,316 **** --- 307,317 ---- // don't commit memory if the entire space is pinned in memory _high += bytes; return true; } + char* previous_high = high(); char* unaligned_new_high = high() + bytes; assert(unaligned_new_high <= high_boundary(), "cannot expand by more than upper boundary"); // Calculate where the new high for each of the regions should be. If *************** *** 401,410 **** --- 402,428 ---- } else { _upper_high += upper_needs; } } + if (AlwaysPreTouch) { + int vm_ps = os::vm_page_size(); + for (char* curr = previous_high; + curr < unaligned_new_high; + curr += vm_ps) { + // Note the use of a write here; originally we tried just a read, but + // since the value read was unused, the optimizer removed the read. + // If we ever have a concurrent touchahead thread, we'll want to use + // a read, to avoid the potential of overwriting data (if a mutator + // thread beats the touchahead thread to a page). There are various + // ways of making sure this read is not optimized away: for example, + // generating the code for a read procedure at runtime. + *curr = 0; + } + } + + _high += bytes; return true; } // A page is uncommitted if the contents of the entire page is deemed unusable. *** src/share/vm/gc_implementation/parallelScavenge/psVirtualspace.cpp- Thu Nov 20 01:14:11 2008 --- src/share/vm/gc_implementation/parallelScavenge/psVirtualspace.cpp Tue Feb 17 10:48:55 2009 *************** *** 1,12 **** #ifdef USE_PRAGMA_IDENT_SRC ! #pragma ident "@(#)psVirtualspace.cpp 1.10 05/05/02 05:14:03 JVM" #endif /* ! * @(#)psVirtualspace.cpp 1.10 05/05/02 * ! * Copyright 2005 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ #include "incls/_precompiled.incl" #include "incls/_psVirtualspace.cpp.incl" --- 1,12 ---- #ifdef USE_PRAGMA_IDENT_SRC ! #pragma ident "%W% %E% %U% JVM" #endif /* ! * %W% %E% * ! * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ #include "incls/_precompiled.incl" #include "incls/_psVirtualspace.cpp.incl" *************** *** 81,90 **** --- 81,99 ---- bool result = special() || os::commit_memory(base_addr, bytes, alignment()); if (result) { _committed_high_addr += bytes; } + if (AlwaysPreTouch) { + for (char* curr = base_addr; + curr < _committed_high_addr; + curr += os::vm_page_size()) { + char tmp = *curr; + *curr = 0; + } + } + return result; } bool PSVirtualSpace::shrink_by(size_t bytes) { assert(is_aligned(bytes), "arg not aligned"); *************** *** 249,258 **** --- 258,276 ---- bool result = special() || os::commit_memory(base_addr, bytes, alignment()); if (result) { _committed_low_addr -= bytes; } + if (AlwaysPreTouch) { + for (char* curr = base_addr; + curr < _committed_high_addr; + curr += os::vm_page_size()) { + char tmp = *curr; + *curr = 0; + } + } + return result; } bool PSVirtualSpaceHighToLow::shrink_by(size_t bytes) { assert(is_aligned(bytes), "arg not aligned");

17-02-2009

EVALUATION This is code from the G1 collector ( 5070073 ). I will attach the changes which are slightly different from thos in the desc. The cu already has these changes to test.

17-02-2009