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Re: [perl #129802] COW performance problems with regexps

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From:
demerphq
Date:
November 4, 2016 14:39
Subject:
Re: [perl #129802] COW performance problems with regexps
Message ID:
CANgJU+UwYC-1TgTWx47StamBqOYFfxjtT-i=GgLqWFiaZ4ykqQ@mail.gmail.com
On 4 November 2016 at 13:53, Tony Cook <tony@develop-help.com> wrote:
> On Fri, Nov 04, 2016 at 12:20:11PM +0200, Niko Tyni wrote:
>> On Sun, Oct 30, 2016 at 11:29:10AM +0100, demerphq wrote:
>>
>> > commit fe546b38f5a7481954f2f933acf85267578058b3
>> > Author: Yves Orton <demerphq@gmail.com>
>> > Date:   Sun Oct 30 11:02:57 2016 +0100
>> >
>> >     fix #129802: sv_grow: remove the overallocation for COW exemption
>> > for powers of 2
>>
>> > commit 7fdc4f5848180e5ae502e30ea783733d0da04086
>> > Author: Yves Orton <demerphq@gmail.com>
>> > Date:   Sun Oct 30 10:56:36 2016 +0100
>> >
>> >     fix perl #129802 - overallocate in concat to ensure we can COW
>>
>> > The first is potentially controversial. So it might get reverted. But
>> > I consider this ticket closed/fixed.
>>
>> Many thanks for your work. Just in case you didn't notice, there was
>> earlier correspondence on this ticket including a comment from Dave with
>> pretty much the same conclusions.
>>
>> As this seems to be a performance regression in 5.20 or so (and was
>> originally reported to Debian as one), is the fix something that could
>> be considered for the maint-* branches?
>
> If 7fdc4f5848 is backported to maint then whatever fix we end up with
> for #129997 will also need to be backported.

Unless there is some concern about the power-of-2 issue, my gut
instinct is that there should be no issues backporting these patches.

Yves


-- 
perl -Mre=debug -e "/just|another|perl|hacker/"

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