* new-features.sgml (ov-new1.7.10): Document large address awareness
of heap and new way to set the default heap size per executable. * setup2.sgml (setup-maxmem): Revamp to explain new method of allocating more heap on a per-executable basis. Drop outdated stuff. Keep shortened description of heap_chunk_in_mb as note.
This commit is contained in:
Corinna Vinschen
parent
ad39174691
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3de2809073
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@ -1,3 +1,11 @@
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2011-08-12 Corinna Vinschen <corinna@vinschen.de>
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* new-features.sgml (ov-new1.7.10): Document large address awareness
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of heap and new way to set the default heap size per executable.
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* setup2.sgml (setup-maxmem): Revamp to explain new method of
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allocating more heap on a per-executable basis. Drop outdated stuff.
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Keep shortened description of heap_chunk_in_mb as note.
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2011-08-04 Corinna Vinschen <corinna@vinschen.de>
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* faq-using.xml (faq.using.bloda): Add NVIDIA. Change wording slightly.
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@ -13,6 +13,20 @@ The CYGWIN environment variable options "envcache", "strip_title", "title",
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"tty", and "upcaseenv" have been removed.
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</para></listitem>
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<listitem><para>
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If the executable (and the system) is large address aware, the application heap
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will be placed in the large memory area. The <command>peflags</command> tool
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from the <literal>rebase</literal> package can be used to set the large
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address awareness flag in the executable file header.
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</para></listitem>
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<listitem><para>
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The registry setting "heap_chunk_in_mb" has been removed, in favor of a new
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per-executable setting in the executable file header which can be set using the
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<command>peflags</command> tool. See <xref linkend="setup-maxmem"></xref>
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for more information.
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</para></listitem>
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<listitem><para>
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The CYGWIN=tty mode using pipes to communicate with the console in a pseudo
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tty-like mode has been removed. Either just use the normal Windows console
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@ -138,65 +138,60 @@ environment. In these cases, you have to call the aforementioned
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Cygwin's heap is extensible. However, it does start out at a fixed size
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and attempts to extend it may run into memory which has been previously
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allocated by Windows. In some cases, this problem can be solved by
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adding an entry in the either the <literal>HKEY_LOCAL_MACHINE</literal>
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(to change the limit for all users) or
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<literal>HKEY_CURRENT_USER</literal> (for just the current user) section
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of the registry. </para>
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changing a field in the file header which is utilized by Cygwin since
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version 1.7.10 to keep the initial size of the application heap. If the
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field contains 0, which is the default, the application heap defaults to
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a size of 384 Megabyte. If the field is set to any other value between 4 and
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2048, Cygwin tries to reserve as much Megabytes for the application heap.
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The field used for this is the "LoaderFlags" field in the NT-specific
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PE header structure (<literal>(IMAGE_NT_HEADER)->OptionalHeader.LoaderFlags</literal>).</para>
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<para>
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Add the <literal>DWORD</literal> value <literal>heap_chunk_in_mb</literal>
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and set it to the desired memory limit in decimal MB. It is preferred to do
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this in Cygwin using the <command>regtool</command> program included in the
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Cygwin package.
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(For more information about <command>regtool</command> or the other Cygwin
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utilities, see <xref linkend="using-utils"></xref> or use the
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<literal>--help</literal> option of each util.) You should always be careful
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when using <command>regtool</command> since damaging your system registry can
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result in an unusable system. This example sets memory limit to 1024 MB:
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This value can be changed for any executable by using a more recent version
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of the <command>peflags</command> tool from the <literal>rebase</literal>
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Cygwin package. Example:
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<screen>
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regtool -i set /HKLM/Software/Cygwin/heap_chunk_in_mb 1024
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regtool -v list /HKLM/Software/Cygwin
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$ peflags --cygwin-heap foo.exe
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foo.exe: initial Cygwin heap size: 0 (0x0) MB
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$ peflags --cygwin-heap=500 foo.exe
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foo.exe: initial Cygwin heap size: 500 (0x1f4) MB
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</screen>
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</para>
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<para>
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Exit all running Cygwin processes and restart them. Memory can be allocated up
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to the size of the system swap space minus any the size of any running
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processes. The system swap should be at least as large as the physically
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installed RAM and can be modified under the System category of the
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Control Panel.
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Heap memory can be allocated up to the size of the biggest available free
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block in the processes virtual memory (VM). By default, the VM per process
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is 2 GB for 32 processes. To get more VM for a process, the executable
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must have the "large address aware" flag set in the file header. You can
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use the aforementioned <command>peflags</command> tool to set this flag.
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On 64 bit systems this results in a 4 GB VM for a process started from that
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executable. On 32 bit systems you also have to prepare the system to allow
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up to 3 GB per process. See the Microsoft article
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<ulink url="http://msdn.microsoft.com/en-us/library/bb613473%28VS.85%29.aspx">4-Gigabyte Tuning</ulink>
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for more information.
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</para>
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<note>
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<para>
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Here is a small program written by DJ Delorie that tests the
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memory allocation limit on your system:
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Older Cygwin releases only supported a global registry setting to
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change the initial heap size for all Cygwin processes. This setting is
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not used anymore. However, if you're running an older Cygwin release
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than 1.7.10, you can add the <literal>DWORD</literal> value
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<literal>heap_chunk_in_mb</literal> and set it to the desired memory limit
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in decimal MB. You have to stop all Cygwin processes for this setting to
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have any effect. It is preferred to do this in Cygwin using the
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<command>regtool</command> program included in the Cygwin package.
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(see <xref linkend="regtool"></xref>) This example sets the memory limit
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to 1024 MB for all Cygwin processes (use HKCU instead of HKLM if you
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want to set this only for the current user):
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<screen>
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main()
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{
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unsigned int bit=0x40000000, sum=0;
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char *x;
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while (bit > 4096)
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{
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x = malloc(bit);
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if (x)
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sum += bit;
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bit >>= 1;
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}
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printf("%08x bytes (%.1fMb)\n", sum, sum/1024.0/1024.0);
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return 0;
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}
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$ regtool -i set /HKLM/Software/Cygwin/heap_chunk_in_mb 1024
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$ regtool -v list /HKLM/Software/Cygwin
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</screen>
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You can compile this program using:
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<screen>
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gcc max_memory.c -o max_memory.exe
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</screen>
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Run the program and it will output the maximum amount of allocatable memory.
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</para>
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</note>
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</sect1>
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