* Re: [gentoo-dev] [RFC] DIGESTS metadata variable for cache validation
@ 2009-02-08 22:14 99% ` Zac Medico
0 siblings, 0 replies; 1+ results
From: Zac Medico @ 2009-02-08 22:14 UTC (permalink / raw
To: gentoo-dev
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Tiziano Müller wrote:
> Am Sonntag, den 08.02.2009, 12:36 -0800 schrieb Zac Medico:
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>> Tiziano Müller wrote:
>>> But if your target is to reduce the size of the metadata cache, why
>>> store the hashes of the eclasses in the ebuild's metadata and not in a
>>> seperate dir? They have to be the same for every ebuild, don't they?
>>> In case you have an average number of eclasses which is bigger than 4,
>>> you can even store the full hash with less space used than with
>>> truncated hashes for all eclasses.
>> The problem with having eclass integrity data shared in a separate
>> file is that it creates a requirement for all cache entries which
>> reference the same eclasses to be consistent with one another. This
>> means that a single cache entry can no longer be updated atomically.
>> For example, before updating the shared eclass integrity data, you'd
>> want to make sure that you first discard all of the cache entries
>> which reference it. Although it can be done this way, I think it's
>> much more convenient to have all of the integrity data encapsulated
>> within each individual cache entry.
> Ok, let me see if I get this: Since parts of the content of a
> metadata-entry (like the DEPEND/RDEPEND vars) depend on the contents of
> the eclass used by the time a cache entry got generated, you want to
> store the eclass' hash in the ebuild entry to make sure the entry gets
> invalidated once the eclass changes. Is that correct?
Right. By having each cache entry encapsulate it's own integrity
data, the program updating the cache is never required to update
more than one file at a time. Having shared integrity data would
imply that the program would have the burden of maintaining
consistency across all cache entries.
- --
Thanks,
Zac
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^ permalink raw reply [relevance 99%]
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2009-02-02 20:34 [gentoo-dev] [RFC] DIGESTS metadata variable for cache validation Zac Medico
2009-02-07 22:31 ` Tiziano Müller
2009-02-07 23:23 ` Zac Medico
2009-02-08 8:07 ` Tiziano Müller
2009-02-08 8:59 ` Zac Medico
2009-02-08 11:51 ` Tiziano Müller
2009-02-08 20:36 ` Zac Medico
2009-02-08 21:48 ` Tiziano Müller
2009-02-08 22:14 99% ` Zac Medico
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