readlink system calls

readlink system calls

[Christopher Baines]

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When looking at strace for various Guile things, I'm seeing a lot of
readlink system calls for directories in the load path, e.g.

readlink("/gnu", 0x7fff8738f430, 1023)  = -1 EINVAL (Invalid argument)
readlink("/gnu/store", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/lkx2k8hy40a6s3vz94287g8fr2sxs7h0-profile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/lkx2k8hy40a6s3vz94287g8fr2sxs7h0-profile/share", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/lkx2k8hy40a6s3vz94287g8fr2sxs7h0-profile/share/guile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/lkx2k8hy40a6s3vz94287g8fr2sxs7h0-profile/share/guile/site", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/lkx2k8hy40a6s3vz94287g8fr2sxs7h0-profile/share/guile/site/3.0", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu", 0x7fff8738f430, 1023)  = -1 EINVAL (Invalid argument)
readlink("/gnu/store", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile/3.0", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu", 0x7fff8738f430, 1023)  = -1 EINVAL (Invalid argument)
readlink("/gnu/store", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile/site", 0x7fff8738f430, 1023) = -1 ENOENT (No such file or directory)
readlink("/gnu", 0x7fff8738f430, 1023)  = -1 EINVAL (Invalid argument)
readlink("/gnu/store", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile/site", 0x7fff8738f430, 1023) = -1 ENOENT (No such file or directory)
readlink("/gnu", 0x7fff8738f430, 1023)  = -1 EINVAL (Invalid argument)
readlink("/gnu/store", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)
readlink("/gnu/store/2429gbw7plqmyb78h2yg67gaqwapv7gm-guile-next-3.0.9-0.aa2cfe7/share/guile", 0x7fff8738f430, 1023) = -1 EINVAL (Invalid argument)


Any idea what leads to this behaviour?

Thanks,

Chris

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Re: readlink system calls

[Olivier Dion]

On Tue, 22 Aug 2023, Christopher Baines <mail@cbaines.net> wrote:
> When looking at strace for various Guile things, I'm seeing a lot of
> readlink system calls for directories in the load path, e.g.

Is this not more a side effect of using Guix (the GNU store) than Guile
itself?

-- 
Olivier Dion
oldiob.dev

Re: readlink system calls

[Maxime Devos]

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Op 22-08-2023 om 21:03 schreef Olivier Dion:
> On Tue, 22 Aug 2023, Christopher Baines <mail@cbaines.net> wrote:
>> When looking at strace for various Guile things, I'm seeing a lot of
>> readlink system calls for directories in the load path, e.g.
> 
> Is this not more a side effect of using Guix (the GNU store) than Guile
> itself?

I'm pretty sure that, store or not, there is probably not a good reason 
Guile is 'readlink'-ing the same directories multiple times.  Even if it 
were a side effect of using Guix, it appears to be something that needs 
to be addressed in Guile.

> Any idea what leads to this behaviour?

Hypothesis:

  * Guile is searching for .go/.scm files in the load paths
  * as part of that this process, it readlinks stuff
    (don't know why Guile would need this information though)
  * it doesn't cache any of this readlink information, so if
    you load N .go/.scm files from the same directory, then the
    number of readlink calls is multiplied by N.

Assuming this hypothesis true, a potential solution could be to cache 
the readlink information.  Whether that's a correct solution depends on 
what the purpose of these readlink calls are ...

Best regards,
Maxime.

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