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

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From:
Tony Cook
Date:
November 4, 2016 12:54
Subject:
Re: [perl #129802] COW performance problems with regexps
Message ID:
20161104125326.GJ10472@mars.tony.develop-help.com
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.

Tony

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