Re: [bug #52076] wildcard/glob should be sorted

[Sven C. Dack]

One thought I have here is that the sorting algorithm itself may not 
have a significant impact, but hard disk latencies may well make a 
difference.

What one sees as an (alphabetically) unordered list may well be an 
ordering significant to a file system's performance, meaning, it's not a 
completely random ordering and sorting it alphabetically can negatively 
impact the file system's efficiency. The ordering in which a file system 
returns file lists will likely be how these are physically ordered on 
the drive, thus processing them in the same exact order will help in 
reducing access latencies.

However, running builds in parallel and using SSDs over HDDs has reduced 
the latency problem significantly in recent years. This will make 
(alphabetically) unordered lists more useful to older systems, but less 
useful to newer ones.

Seeing how this isn't useful to everyone, how about making it into a 
--disable/--enable option for configure?


On 21/09/17 04:26, Bernhard M. wrote:
> Follow-up Comment #2, bug #52076 (project make):
>
> I tried to measure the performance difference using the attached 'makebench'
> files, running in a tmpfs to not have physical disk IO influence results
> but found that the difference is so close to zero
> that it was lost in noise.
>
>
> Here is what i got from running it twice each with unsorted and sorted glob:
>
> ==unsorted make:
>
> real    0m8,108s
> user    0m7,652s
> sys     0m0,402s
> make: Nothing to be done for 'run'.
>
> real    0m7,706s
> user    0m7,496s
> sys     0m0,157s
>
>
> real    0m7,998s
> user    0m7,605s
> sys     0m0,391s
> make: Nothing to be done for 'run'.
>
> real    0m7,634s
> user    0m7,489s
> sys     0m0,136s
>
>
> == sorted make:
>
> real    0m8,030s
> user    0m7,662s
> sys     0m0,372s
> make: Nothing to be done for 'run'.
>
> real    0m7,583s
> user    0m7,417s
> sys     0m0,168s
>
>
> real    0m8,026s
> user    0m7,609s
> sys     0m0,423s
> make: Nothing to be done for 'run'.
>
> real    0m7,646s
> user    0m7,509s
> sys     0m0,137s
>
>
> Do you have a benchmark that better shows the difference?
>
> (file #41853)
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> Additional Item Attachment:
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> File name: makebench.tar.gz               Size:0 KB
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