> Adding in core-libs-dev as there's nothing related to hotspot directly
here.
>
> David
Thought it was best to pass this through hotspot lists first, as full
completion
of the native side of things will probably require hotspot changes.
You're quite right though, I should have cc'd hotspot *and* core libs.
- Adam
>
> On 14/02/2018 9:32 PM, Adam Farley8 wrote:
>> Hi All,
>>
>> Currently, diagnostic core files generated from OpenJDK seem to lump
all
>> of the
>> native memory usages together, making it near-impossible for someone to
>> figure
>> out *what* is using all that memory in the event of a memory leak.
>>
>> The OpenJ9 VM has a feature which allows it to track the allocation of
>> native
>> memory for Direct Byte Buffers (DBBs), and to supply that information
into
>> the
>> cores when they are generated. This makes it a *lot* easier to find out
>> what is using
>> all that native memory, making memory leak resolution less like some
dark
>> art, and
>> more like logical debugging.
>>
>> To use this feature, there is a native method referenced in
Unsafe.java.
>> To open
>> up this feature so that any VM can make use of it, the java code below
>> sets the
>> stage for it. This change starts letting people call DBB-specific
methods
>> when
>> allocating native memory, and getting into the habit of using it.
>>
>> Thoughts?
>>
>> Best Regards
>>
>> Adam Farley
>>
>> P.S. Code:
>>
>> diff --git
>> a/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template
>> b/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template
>> ---
a/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template
>> +++
b/src/java.base/share/classes/java/nio/Direct-X-Buffer.java.template
>> @@ -85,7 +85,7 @@
>> // Paranoia
>> return;
>> }
>> - UNSAFE.freeMemory(address);
>> + UNSAFE.freeDBBMemory(address);
>> address = 0;
>> Bits.unreserveMemory(size, capacity);
>> }
>> @@ -118,7 +118,7 @@
>>
>> long base = 0;
>> try {
>> - base = UNSAFE.allocateMemory(size);
>> + base = UNSAFE.allocateDBBMemory(size);
>> } catch (OutOfMemoryError x) {
>> Bits.unreserveMemory(size, cap);
>> throw x;
>> diff --git a/src/java.base/share/classes/jdk/internal/misc/Unsafe.java
>> b/src/java.base/share/classes/jdk/internal/misc/Unsafe.java
>> --- a/src/java.base/share/classes/jdk/internal/misc/Unsafe.java
>> +++ b/src/java.base/share/classes/jdk/internal/misc/Unsafe.java
>> @@ -632,6 +632,26 @@
>> }
>>
>> /**
>> + * Allocates a new block of native memory for DirectByteBuffers,
of
>> the
>> + * given size in bytes. The contents of the memory are
>> uninitialized;
>> + * they will generally be garbage. The resulting native pointer
will
>> + * never be zero, and will be aligned for all value types. Dispose
>> of
>> + * this memory by calling {@link #freeDBBMemory} or resize it with
>> + * {@link #reallocateDBBMemory}.
>> + *
>> + * @throws RuntimeException if the size is negative or too large
>> + * for the native size_t type
>> + *
>> + * @throws OutOfMemoryError if the allocation is refused by the
>> system
>> + *
>> + * @see #getByte(long)
>> + * @see #putByte(long, byte)
>> + */
>> + public long allocateDBBMemory(long bytes) {
>> + return allocateMemory(bytes);
>> + }
>> +
>> + /**
>> * Resizes a new block of native memory, to the given size in
bytes.
>> The
>> * contents of the new block past the size of the old block are
>> * uninitialized; they will generally be garbage. The resulting
>> native
>> @@ -687,6 +707,27 @@
>> }
>>
>> /**
>> + * Resizes a new block of native memory for DirectByteBuffers, to
the
>> + * given size in bytes. The contents of the new block past the
size
>> of
>> + * the old block are uninitialized; they will generally be
garbage.
>> The
>> + * resulting native pointer will be zero if and only if the
requested
>> size
>> + * is zero. The resulting native pointer will be aligned for all
>> value
>> + * types. Dispose of this memory by calling {@link
#freeDBBMemory},
>> or
>> + * resize it with {@link #reallocateDBBMemory}. The address
passed
>> to
>> + * this method may be null, in which case an allocation will be
>> performed.
>> + *
>> + * @throws RuntimeException if the size is negative or too large
>> + * for the native size_t type
>> + *
>> + * @throws OutOfMemoryError if the allocation is refused by the
>> system
>> + *
>> + * @see #allocateDBBMemory
>> + */
>> + public long reallocateDBBMemory(long address, long bytes) {
>> + return reallocateMemory(address, bytes);
>> + }
>> +
>> + /**
>> * Sets all bytes in a given block of memory to a fixed value
>> * (usually zero).
>> *
>> @@ -918,6 +959,17 @@
>> checkPointer(null, address);
>> }
>>
>> + /**
>> + * Disposes of a block of native memory, as obtained from {@link
>> + * #allocateDBBMemory} or {@link #reallocateDBBMemory}. The
address
>> passed
>> + * to this method may be null, in which case no action is taken.
>> + *
>> + * @see #allocateDBBMemory
>> + */
>> + public void freeDBBMemory(long address) {
>> + freeMemory(address);
>> + }
>> +
>> /// random queries
>>
>> /**
>>
>> Unless stated otherwise above:
>> IBM United Kingdom Limited - Registered in England and Wales with
number
>> 741598.
>> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU
>>
>
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
