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By storing the size of the string in the cache, we can make use of
it when comparing the names in the hashtable in pkgCache::FindGrp.
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It makes no sense to check if the value is empty, as it cannot
be. It will always be a hexstring of exactly 32 bytes.
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Instead of storing a string -> map_stringitem_t mapping, create
our own data type that can point to either a normal string or
a string inside the cache.
This avoids the creation of any string and improves performance
slightly (about 4%).
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This improves performance, as we now can ignore unequal strings
based on their length already.
Gbp-Dch: ignore
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This removes some minor overhead.
Gbp-Dch: ignore
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Moving the string is likely faster than copying it. We could probably
avoid strings alltogether in the future using some more crazy code,
but I have not looked at that yet.
Gbp-Dch: ignore
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This improves performance of the cache generation on my
ARM platform (4x Cortex A15) by about 10% to 20% from
2.35-2.50 to 2.1 seconds.
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Integrity is taken care of by the checksum now.
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If we already have opened a cache, there is no point in having
to open it again.
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std::unordered_map is faster than std::map in our use case,
reducing cache generation time by about 10% in my benchmark.
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Git-Dch: Ignore
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Out of memory and similar circumstanzas could cause MMap::Map to fail
and especially the mmap/malloc calls in it. With some additional
checking we can avoid segfaults and similar in such situations – at
least in theory as if this is a real out of memory everything we do to
handle the error could just as well run into a memory problem as well…
But at least in theory (if MMap::Map is made to fail always) we can deal
with it so good that a user actually never sees a failure (as the cache
it tries to load with it fails and is discarded, so that DynamicMMap
takes over and a new one is build) instead of segfaulting.
Closes: 803417
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Reported-By: cppcheck
Git-Dch: Ignore
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Reported-By: Konomi on IRC
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Our error reporting is historically grown into some kind of mess.
A while ago I implemented stacking for the global error which is used in
this commit now to wrap calls to functions which do not report (all)
errors via return, so that only failures in those calls cause a failure
to propergate down the chain rather than failing if anything
(potentially totally unrelated) has failed at some point in the past.
This way we can avoid stopping the entire acquire process just because a
single source produced an error for example. It also means that after
the acquire process the cache is generated – even if the acquire
process had failures – as we still have the old good data around we can and
should generate a cache for (again).
There are probably more instances of this hiding, but all these looked
like the easiest to work with and fix with reasonable (aka net-positive)
effects.
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How the Multi-Arch field and pkg:<arch> dependencies interact was
discussed at DebConf15 in the "MultiArch BoF". dpkg and apt (among other
tools like dose) had a different interpretation in certain scenarios
which we resolved by agreeing on dpkg view – and this commit realizes
this agreement in code.
As was the case so far libapt sticks to the idea of trying to hide
MultiArch as much as possible from individual frontends and instead
translates it to good old SingleArch. There are certainly situations
which can be improved in frontends if they know that MultiArch is upon
them, but these are improvements – not necessary changes needed
to unbreak a frontend.
The implementation idea is simple: If we parse a dependency on foo:amd64
the dependency is formed on a package 'foo:amd64' of arch 'any'. This
package is provided by package 'foo' of arch 'amd64', but not by 'foo'
of arch 'i386'. Both of those foo packages provide each other through
(assuming foo is M-A:foreign) to allow a dependency on 'foo' to be
satisfied by either foo of amd64 or i386. Packages can also declare to
provide 'foo:amd64' which is translated to providing 'foo:amd64:any' as
well.
This indirection over provides was chosen as the alternative would be to
teach dependency resolvers how to deal with architecture specific
dependencies – which violates the design idea of avoiding resolver
changes, especially as architecture-specific dependencies are a
cornercase with quite a few subtil rules. Handling it all over versioned
provides as we already did for M-A in general seems much simpler as it
just works for them.
This switch to :any has actually a "surprising" benefit as well: Even
frontends showing a package name via .Name() [which doesn't show the
architecture] will display the "architecture" for dependencies in which
it was explicitely requested, while we will not show the 'strange' :any
arch in FullName(true) [= pretty-print] either. Before you had to
specialcase these and by default you wouldn't get these details shown.
The only identifiable disadvantage is that this complicates error
reporting and handling. apt-get's ShowBroken has existing problems with
virtual packages [it just shows the name without any reason], so that
has to be worked on eventually. The other case is that detecting if a
package is completely unknown or if it was at least referenced somewhere
needs to acount for this "split" – not that it makes a practical
difference which error is shown… but its one of the improvements
possible.
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The parameter name suggests that it should forbid the building of the
entire cache in memory, but this isn't how it was previously and as
AllowMem is false by default it actually prevents previous usecases from
working like being root and configuring apt to build no caches at all.
This should be fixed at some point to actually work, but that is hard to
pull off as it means switching the default and some callers (including
apt itself) actually did call it explicitly with false in certain
cases for no apparent reason (at least now where it is common to have
enough memory to throw at every problem and even if not is a slow apt
usally better than an apt erroring out).
Closes: 796459
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After fixing Bug#796999, we noticed that there were
some more instances of iterators which had no associated
Dynamic object, causing them to not be updated when
the cache was remapped.
This happened in two places: In NewPackage() and in
NewProvidesAllArch().
Gbp-Dch: ignore
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In both the Ver and Dep variables, we need to account for remapping,
as otherwise we would still reference the old bug.
Reproduction environment:
* An i386 system with amd64 foreign architecture
* A sources.list with
deb http://snapshot.debian.org/archive/debian/20150826T102846Z/ unstable main
deb http://snapshot.debian.org/archive/debian/20150826T102846Z/ experimental main
Thanks: Jakub Wilk for the bug report and the backtraces
Closes: #796999
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More standardization
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Switch to std::unique_ptr, as this is safer than SPtr.
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We archieve the same without the special handling now, so drop this code.
Makes supporting this abdomination a little longer bearable as well.
Git-Dch: Ignore
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The code was never active in production, it just sits there collecting
dust and given that it is never tested probably doesn't even work
anymore the way it was supposed to be (whatever that was exactly in the
first place). So just remove it before I have to "fix" it again next
time.
Git-Dch: Ignore
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Trade deduplication of code for a bunch of new virtuals, so it is
actually visible how the different indexes behave cleaning up the
interface at large in the process.
Git-Dch: Ignore
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Sources are usually defined in sources.list (and co) and are pretty
stable, but once in a while a frontend might want to add an additional
"source" like a local .deb file to install this package (No support for
'real' sources being added this way as this is a multistep process).
We had a hack in place to allow apt-get and apt to pull this of for a
short while now, but other frontends are either left in the cold by this
and/or the code for it looks dirty with FIXMEs plastering it and has on
top of this also some problems (like including these 'volatile' sources
in the srcpkgcache.bin file).
So the biggest part in this commit is actually the rewrite of the cache
generation as it is now potentially a three step process. The biggest
problem with adding support now through is that this makes a bunch of
previously mostly unusable by externs and therefore hidden classes
public, so a bit of further tuneing on this now public API is in order…
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Now that we deal with provides in a more dynamic fashion the last
remaining problem is explicit dependencies like 'Conflicts: foo' which
have to apply to all architectures, but creating them all at the same
time requires us to know all architectures ending up in the cache which
isn't needed to be the same set as all foreign architectures.
The effect is visible already now through as this prevents the creation
of a bunch of virtual packages for arch:all packages and as such also
many dependencies, just not very visible if you don't look at the stats…
Git-Dch Ignore
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Expecting the worst is easy to code, but has its disadvantages e.g.
by creating package structures which otherwise would have never
existed. By creating the provides instead at the time a package
structure is added we are well prepared for the introduction of partial
architectures, massive amounts of M-A:foreign (and :allowed) and co as
far as provides are concerned at least. We have something relatively
similar for dependencies already.
Many tests are added for both M-A states and the code cleaned to
properly support implicit provides for foreign architectures and
architectures we 'just' happen to parse.
Git-Dch: Ignore
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Before MultiArch implicits weren't a thing, so they were hidden by
default by definition. Adding them for MultiArch solved many problems,
but having no reliable way of detecting which dependency (and provides)
is implicit or not causes problems everytime we want to output
dependencies without confusing our observers with unneeded
implementation details.
The really notworthy point here is actually that we keep now a better
record of how a dependency came to be so that we can later reason about
it more easily, but that is hidden so deep down in the library internals
that change is more the problems it solves than the change itself.
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Cache generation needs a way of quickly iterating over the unique potion
of the dependencies to be able to share them. By linking them together
we can reduce the speed penality (~ 80%) with only a small reduction in
saved size (~ 20%).
Git-Dch: Ignore
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Having dependency data separated from the link between version/package
and the dependency allows use to work on sharing the depdency data a bit
as it turns out that many dependencies are in fact duplicates. How many
are duplicates various heavily with the sources configured, but for a
single Debian release the ballpark is 2 duplicates for each dependency
already (e.g. libc6 counts 18410 dependencies, but only 45 unique). Add
more releases and the duplicates count only rises to get ~6 for 3
releases. For each architecture a user has configured which given the
shear number of dependencies amounts to MBs of duplication.
We can cut down on this number, but pay a heavy price for it: In my
many releases(3) + architectures(3) test we have a 10% (~ 0.5 sec)
increase in cache creationtime, but also 10% less cachesize (~ 10 MB).
Further work is needed to rip the whole benefits from this through, so
this is just the start.
Git-Dch: Ignore
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Doing this disables the implicit copy assignment operator (among others)
which would cause hovac if used on the classes as it would just copy the
pointer, not the data the d-pointer points to. For most of the classes
we don't need a copy assignment operator anyway and in many classes it
was broken before as many contain a pointer of some sort.
Only for our Cacheset Container interfaces we define an explicit copy
assignment operator which could later be implemented to copy the data
from one d-pointer to the other if we need it.
Git-Dch: Ignore
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To have a chance to keep the ABI for a while we need all three to team
up. One of them missing and we might loose, so ensuring that they are
available is a very tedious but needed task once in a while.
Git-Dch: Ignore
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This is mainly visible in the policy, so that you can now pin by b= and
let it only effect Packages files of this architecture and hence the
packages coming from it (which do not need to be from this architecture,
but very likely are in a normal repository setup).
If you should pin by architecture in this way is a different question…
Closes: 687255
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Selecting targets based on the Release they belong to isn't to
unrealistic. In fact, it is assumed to be the most used case so it is
made the default especially as this allows to bundle another thing we
have to be careful with: Filenames and only showing targets we have
acquired.
Closes: 752702
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We used to read the Release file for each Packages file and store the
data in the PackageFile struct even through potentially many Packages
(and Translation-*) files could use the same data. The point of the
exercise isn't the duplicated data through. Having the Release files as
first-class citizens in the Cache allows us to properly track their
state as well as allows us to use the information also for files which
aren't in the cache, but where we know to which Release file they
belong (Sources are an example for this).
This modifies the pkgCache structs, especially the PackagesFile struct
which depending on how libapt users access the data in these structs can
mean huge breakage or no visible change. As a single data point:
aptitude seems to be fine with this. Even if there is breakage it is
trivial to fix in a backportable way while avoiding breakage for
everyone would be a huge pain for us.
Note that not all PackageFile structs have a corresponding ReleaseFile.
In particular the dpkg/status file as well as *.deb files have not. As
these have only a Archive property need, the Component property takes
over this duty and the ReleaseFile remains zero. This is also the reason
why it isn't needed nor particularily recommended to change from
PackagesFile to ReleaseFile blindly. Sticking with the earlier is
usually the better option.
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The change itself is no problem ABI wise, but the remove of the old
undynamic hashtables is, so we bring it back for older abis and happily
use the now available free space to backport more recent additions like
the dynamic hashtable itself.
Git-Dch: Ignore
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For compatibility we use/provide and fill quiet some deprecated methods
and fields, which subsequently earns us a warning for using them. These
warnings therefore have to be disabled for these codeparts and that is
what this change does now in a slightly more elegant way.
Git-Dch: Ignore
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aptitude has a define for VERSION, so to not generate a FTBFS we just
rename our enum element to a slightly less generic name.
Git-Dch: Ignore
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Git-Dch: Ignore
Reported-By: cppcheck
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Turns out that version numbers aren't as random as you might guess.
In my cache for example, I have:
Total package names: 69513 (1390 k)
Total package structures: 188259 (9036 k)
Total distinct versions: 186345 (13.4 M)
Total dependencies: 2052242 (57.5 M)
which amounts to 1035873 (10,1 M) strings.
Reusing version strings reduces this to 161465 (3.479 k).
This comes at a cost of course: Generation is slightly slower, but we
are still faster than what we started with and it makes room (also cache
size wise) for further changes.
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Strings like Section names or architectures are needed vary often.
Instead of writing them each time we need them, we deploy sharing for
these special strings. Until now, this was done with a linked list of
strings in which we would search, which was stored in the cache.
It turns out we can do this just as well in memory as well with a bunch
of std::map's.
In memory means here that it isn't available anymore if we have a partly
invalid cache, but that isn't much of a problem in practice as the
status file is compared to the other files we parse very small and includes
mostly duplicates, so the space we would gain by storing is more or less
equal to the size of the stored linked list…
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They both store the same information, so this field just takes up space
in the Package struct for no good reason. We mark it "just" as deprecated
instead of instantly removing it though as it isn't misleading like
Section was and is potentially used in the wild more often.
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It still doesn't reflect the size the cache has on the disk compared to
what is given as total size (90 vs 103 MB), but by counting all structs
in we are at least a bit closer to the reality.
Git-Dch: ignore
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We had a wild mixture of (unsigned) int, long and long long here without
much sense, so this commit adds a few typedefs to get some sense in the
typesystem and ensures that a ID isn't sometimes computed as int, stored
as long and compared with a long long… as this could potentially bite us
later on as the size of the archive only increases over time.
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It also makes the size configureable, so it can be adapted in the future
without the need for an abi break - and even by users…
The increase was long overdue as it gives a >10% decrease in runtime of
e.g. 'apt-get check -s'. Some (useless) benchmark with 69933 groups and
187796 packages without a pre-built cache:
time apt-get check -so APT::Cache-HashTableSize=1 → 20m
time apt-get check -so APT::Cache-HashTableSize=1000 → 6,41s
time apt-get check -so APT::Cache-HashTableSize=2000 → 5,64s (old)
time apt-get check -so APT::Cache-HashTableSize=3000 → 5,30s
time apt-get check -so APT::Cache-HashTableSize=5000 → 5,08s
time apt-get check -so APT::Cache-HashTableSize=6000 → 5,05s
time apt-get check -so APT::Cache-HashTableSize=7000 → 5,02s
time apt-get check -so APT::Cache-HashTableSize=8000 → 5,00s
time apt-get check -so APT::Cache-HashTableSize=9000 → 4,98s
time apt-get check -so APT::Cache-HashTableSize=10000 → 4,96s (new)
time apt-get check -so APT::Cache-HashTableSize=15000 → 4,90s
time apt-get check -so APT::Cache-HashTableSize=20000 → 4,86s
time apt-get check -so APT::Cache-HashTableSize=30000 → 4,77s
time apt-get check -so APT::Cache-HashTableSize=40000 → 4,74s
time apt-get check -so APT::Cache-HashTableSize=50000 → 4,73s
time apt-get check -so APT::Cache-HashTableSize=60000 → 4,71s
The gap increases further for operations which have more package
lookups. Factor 5 was chosen as higher values do not provide any
really significant timing advantage anymore compared to the memory
increase in my testing and there is always the possibility to increase
it now if that changes. (also most users will not have 3 releases and
4 architectures in the cache, so theirs will be much smaller and faster).
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Conflicts:
apt-pkg/acquire-item.cc
apt-pkg/acquire-item.h
apt-pkg/deb/debmetaindex.h
apt-pkg/pkgcache.cc
test/integration/test-apt-ftparchive-src-cachedb
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This is a internal struct not a external interface so the actual
breakage should be small.
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