Req #50486 [Asn->Csd]: [PATCH] optimization for safe_address on exotic platforms

Edit report at https://bugs.php.net/bug.php?id=50486&edit=1 ID: 50486 Updated by: nikic@php.net Reported by: basant dot kukreja at gmail dot com Summary: [PATCH] optimization for safe_address on exotic platforms -Status: Assigned +Status: Closed Type: Feature/Change Request Package: Performance problem Operating System: Solaris 10 PHP Version: 5.3SVN-2009-12-16 (SVN) Assigned To: dmitry Block user comment: N Private report: N New Comment: I believe this is no longer relevant, as the zend_multiply() code uses __builtin_smulll_overflow() nowadays. Previous Comments: ------------------------------------------------------------------------ [2016-08-06 02:37:55] kalle@php.net Dmitry, any input on this? ------------------------------------------------------------------------ [2009-12-16 01:35:09] basantk@php.net On a ecommerce benchmark on Solaris sparc, new implementation reduced the time spent in _ecalloc to 50%. ------------------------------------------------------------------------ [2009-12-16 01:34:07] basantk@php.net Microbenchmark testing on Linux x86_64 : ======================================= Based on the above suggested implementation, I benchmarked 3 implementation of safe_address on Linux x86_64 (fedora 11) using a micro benchmark. Here are the results : -------------------------------------- For a regular nmemb * size + offset when no overflow possible : nmemb = 23456 size = 67890 offset = 12345 assembly version of safe_address time diff = 26 ticks doubles imlementation of safe_address time diff = 72 ticks proposed safe_address time diff = 30 ticks -------------------------------------- For bigger integer multiplication : nmemb = 2589934591 size = 4294967295 offset = 5 assembly version of safe_address time diff = 26 ticks doubles imlementation of safe_address time diff = 75 ticks proposed safe_address time diff = 76 ticks -------------------------------------- Here is the micro benchmark link : http://bitbucket.org/basantk/php53perfpatches/src/tip/safe_address_bench.c ------------------------------------------------------------------------ [2009-12-16 01:33:06] basantk@php.net Here is the link to the proposed patch : http://bitbucket.org/basantk/php53perfpatches/raw/ca263ffd272b/safe_address_64bitopt_php53.txt Richard Smith did the original work and I refined the patch. In this proposed optimization we can check if the inputs are sufficiently large enough so that overflow is possible. If overflow is possible, regular double logic will follow. Link the the mail sent to internals mailing list : http://marc.info/?l=php-internals&m=126084384813237&w=2 ------------------------------------------------------------------------ [2009-12-16 01:30:34] basant dot kukreja at gmail dot com Description: ------------ safe_address function calculates nmemb * size + offset and it want to make sure that it output doesn't overflow. It uses doubles for finding overflow which is very inefficent for platforms like sparc. Reproduce code: --------------- Any Php script causes _ecalloc function. Expected result: ---------------- Good performance on platform other than gcc + x86_64 combo. Actual result: -------------- Poor _ecalloc performance on plaforms like Solaris. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=50486&edit=1