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[perl #122629] [PATCH] sv_grow: performance improvement for short strings

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From:
Karl Williamson via RT
Date:
August 31, 2014 04:31
Subject:
[perl #122629] [PATCH] sv_grow: performance improvement for short strings
Message ID:
rt-4.0.18-26569-1409459480-230.122629-14-0@perl.org
On Sat Aug 30 21:11:52 2014, khw wrote:
> I am reopening this ticket and raising its priority because this patch
> breaks blead under ASAN.  Attached is an output of ASAN on
> t/op/attrs.t (uni/attrs.t is also broken)
> 
> 880c169bb2bd5e6e9ae996842d6860bf88d28585 is the first bad commit
> commit 880c169bb2bd5e6e9ae996842d6860bf88d28585
> Author: Reini Urban <rurban@x-ray.at>
> Date:   Wed Aug 27 12:48:35 2014 -0500
> 
> sv_grow: performance improvement for short strings
> 
> Empty COW strings with CUR=0 ended up allocated as LEN=10.
> Now they are rounded up to 4 or 8.
> 
> Timings:
> +0   16.394324103 0.27%
> +2   16.114379842 0.01%
> +4   16.305622265 1.03%
> +8   16.337438609 1.30%
> +10  16.675009468 0.59%
> with LD_LIBRARY_PATH=`pwd` perf stat -r2 ./perl t/harness t/op/*.t
> 
> +2 was consistently the best number, and +10 the worst.
> 
> :100644 100644 5a77d6bd438396bd06e58ed4685d57eca178541b
> 2940942fc6333dd91dcd2acb17bbd558171680ee M      sv.c
> bisect run success
> That took 3158 seconds


-- 
Karl Williamson

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