Messages in this thread | | | From | Denys Vlasenko <> | Subject | [PATCH 0/1] vsprintf: optimize decimal conversion (again) | Date | Mon, 26 Mar 2012 20:47:17 +0200 |
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Hi Andrew,
Can you take this patch into -mm?
Michal, Jones - can you review the code?
Sometime ago, Michal Nazarewicz <mina86@mina86.com> optimized our (already fast) decimal-to-string conversion even further. Somehow this effort did not reach the kernel.
Here is a new iteration of his code.
Optimizations and patch follow in next email.
Please find test programs attached.
32-bit test programs were built using gcc 4.6.2 64-bit test programs were built using gcc 4.2.1 Command line: gcc --static [-m32] -O2 -Wall test_{org,new}.c
Sizes: org32.o: 2850 bytes new32.o: 2858 bytes org64.o: 2155 bytes new64.o: 2283 bytes
Correctness: I tested first and last 40 billion values from [0, 2^64-1] range, they all produced correct result.
Speed: I measured how many thousands of conversions per second are done, for several values (it takes different amount of time to convert, say, 123 and 2^64-1 to their string representations). Format of data below: VALUE:THOUSANDS_OF_CONVS_PER_SEC.
Intel Core i7 2.7GHz: org32: 8:46852 123:39252 123456:23992 12345678:21992 123456789:21048 2^32-1:20424 2^64-1:10216 new32: 8:55300 123:43208 123456:34456 12345678:31272 123456789:23584 2^32-1:23568 2^64-1:16720
AMD Phenom II X4 2.4GHz: org32: 8:29244 123:23988 123456:13792 12345678:12056 123456789:11368 2^32-1:10804 2^64-1:5224 new32: 8:38040 123:30356 123456:22832 12345678:20676 123456789:13556 2^32-1:13472 2^64-1:9228
org64: 8:38664 123:29256 123456:19188 12345678:16320 123456789:15380 2^32-1:14896 2^64-1:7864 new64: 8:42664 123:31660 123456:21632 12345678:19220 123456789:20880 2^32-1:17580 2^64-1:9596
Summary: in all cases new code is faster than old one, in many cases by 30%, in few cases by more than 50% (for example, on x86-32, conversion of num=12345678). Code growth is ~0 in 32-bit case and ~130 bytes in 64-bit case.
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