Unsafe.{get,put}-X-Unaligned performance (original) (raw)

Paul Sandoz paul.sandoz at oracle.com
Wed Mar 11 18:00:13 UTC 2015

Hi Andrew,

On Mar 11, 2015, at 6:27 PM, Andrew Haley <aph at redhat.com> wrote:

On 03/11/2015 07:10 AM, John Rose wrote:

John: I'm waiting for an answer to my question here before I submit a webrev for approval. http://mail.openjdk.java.net/pipermail/panama-dev/2015-March/000099.html (Answered.) http://cr.openjdk.java.net/~aph/unaligned.jdk.5/ http://cr.openjdk.java.net/~aph/unaligned.hotspot.5/ I hope everybody is happy with this, or at least not so unhappy that they would want to reject it altogether.

Some minor comment on the JavaDoc.

I think it more preferable to refer to "underlying platform" or "platform" rather than "machine", at least thats the kind of language i have seen commonly used in other places.

1062 * The write will be atomic with respect to the largest power of 1063 * two that divides the GCD of the offset and the storage size. 1064 * For example, getLongUnaligned will make atomic reads of 2-, 4-, 1065 * or 8-byte storage units if the offset is zero mod 2, 4, or 8, 1066 * respectively. There are no other guarantees of atomicity. 1067 *

1068 * 1069 * @param o Java heap object in which the value resides, if any, else 1070 * null 1071 * @param offset The offset in bytes from the start of the object 1072 * @param x the value to store 1073 * @throws RuntimeException No defined exceptions are thrown, not even 1074 * {@link NullPointerException} 1075 * @since 1.9 1076 */ 1077 public final void putLongUnaligned(Object o, long offset, long x) {

s/reads/writes.

In the example it might be worth pointing out that is for 64-bit systems?

There is no bug ID for this yet. John, would you like to create a bug database entry? If not, I'll do so. Then I can go for a RFR, which hopefully should be a shoo-in now that we've beaten this thing to death. :-)

We need to include some unit tests before we can push. As i said, if you like i can help you with that and also performing a JPRT run across multiple platforms.

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