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Re: Migration despite an RC bug?

Don Armstrong <don@debian.org> writes:
> On Tue, 03 Jan 2017, Ian Jackson wrote:

>> Also, have you checked whether your DB library properly throws errors
>> on writes to a tied hash ?

> I don't know whether it does or not; I went looking to see whether you
> could trap errors on untie(), and untie doesn't return anything useful
> that you can check.

If you're using DB_File, I think you have to use the explicit put() and
get() API instead of the tied magical hash in order to get error

>> Also, I'm not sure why it would be "incredibly slow". In a
>> singlethreaded cpubound task (the worst case) I wouldn't expect worse
>> than a 50% slowdown.

> I wouldn't have expected that either, but it appeared to be 4-5 times
> slower than the equivalent code with fork a decompressor, which is why I
> swapped it out. [I didn't bother to benchmark them, because the
> differences between them was so stark.]

I've done extensive benchmarking of this in Perl for a different project
and yes, fork and exec of an external compresser is *way* faster than
using a library.  I suspect the Perl compress libraries are making
extraneous data copies or doing something else suboptimal.

Russ Allbery (rra@debian.org)               <http://www.eyrie.org/~eagle/>

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