RFR 8017540: Improve multi-threaded contention behavior of BigInteger.toString() radix conversion cache (original) (raw)

Dmitry Nadezhin dmitry.nadezhin at gmail.com
Wed Jun 26 06:53:24 UTC 2013

We could check for the existing cacheLine.length right before installing the new one

Do you mean something like this ?

BigInteger getRadixConversionCache(int radix, int exponent) { BigInteger[] cacheLine = powerCache[radix]; // volatile read if (exponent < cacheLine.length) return cacheLine[exponent];

int oldLength = cacheLine.length; cacheLine = Arrays.copyOf(cacheLine, exponent + 1); for (int i = oldLength; i < exponent + 1; i++) cacheLine[i] = cacheLine[i - 1].square();

if (exponent >= powerCache[radix].length) { // volatile read again BigInteger[][] pc = Arrays.copyOf(powerCache); pc[radix] = cacheLine; powerCache = pc; // volatile write, publish } return cacheLine[exponent]; }

On Wed, Jun 26, 2013 at 10:31 AM, Aleksey Shipilev < aleksey.shipilev at oracle.com> wrote:

On 26.06.2013, at 7:31, Dmitry Nadezhin <dmitry.nadezhin at gmail.com> wrote:

> We have two versions after private discussion with Aleksey. > > BigInteger getRadixConversionCache(int radix, int exponent) { > BigInteger[][] pc = powerCache; // volatile read > BigInteger[] cacheLine = pc[radix]; > if (exponent < cacheLine.length)_ _> return cacheLine[exponent]; > > int oldSize = cacheLine.length; > cacheLine = Arrays.copyOf(cacheLine, exponent + 1); > for (int i = oldSize; i < exponent + 1; i++)_ _> cacheLine[i] = cacheLine[i - 1].square(); > > pc = Arrays.copyOf(powerCache); > pc[radix] = cacheLine; > powerCache = pc; // volatile write, publish > return cacheLine[exponent]; > } Thanks, I like this version a lot better. We could check for the existing cacheLine.length right before installing the new one, so the opportunity to overwrite larger cacheLine would be minimal, but I do think the probability of unlucky timing is very low, and the argument is moot :) Let's keep it simple. -Aleksey.

More information about the core-libs-dev mailing list