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We reintroduce hashmap.{h,c}, list.h and set.h verbatim from upstream,
before we punt dead code. The following is the upstream message:
This is a rewrite of the hashmap implementation. Its advantage is lower
memory usage.
It uses open addressing (entries are stored in an array, as opposed to
linked lists). Hash collisions are resolved with linear probing and
Robin Hood displacement policy. See the references in hashmap.c.
Some fun empirical findings about hashmap usage in systemd on my laptop:
- 98 % of allocated hashmaps are Sets.
- Sets contain 78 % of all entries, plain Hashmaps 17 %, and
OrderedHashmaps 5 %.
- 60 % of allocated hashmaps contain only 1 entry.
- 90 % of allocated hashmaps contain 5 or fewer entries.
- 75 % of all entries are in hashmaps that use trivial_hash_ops.
Clearly it makes sense to:
- store entries in distinct entry types. Especially for Sets - their
entries are the most numerous and they require the least information
to store an entry.
- have a way to store small numbers of entries directly in the hashmap
structs, and only allocate the usual entry arrays when the direct
storage is full.
The implementation has an optional debugging feature (enabled by
defining the ENABLE_HASHMAP_DEBUG macro), where it:
- tracks all allocated hashmaps in a linked list so that one can
easily find them in gdb,
- tracks which function/line allocated a given hashmap, and
- checks for invalid mixing of hashmap iteration and modification.
Since entries are not allocated one-by-one anymore, mempools are not
used for entries. Originally I meant to drop mempools entirely, but it's
still worth it to use them for the hashmap structs. My testing indicates
that it makes loading of units about 5 % faster (a test with 10000 units
where more than 200000 hashmaps are allocated - pure malloc: 449±4 ms,
mempools: 427±7 ms).
Here are some memory usage numbers, taken on my laptop with a more or
less normal Fedora setup after booting with SELinux disabled (SELinux
increases systemd's memory usage significantly):
systemd (PID 1) Original New Change
dirty memory (from pmap -x 1) [KiB] 2152 1264 -41 %
total heap allocations (from gdb-heap) [KiB] 1623 756 -53 %
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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This way we can use it on non-const strings, and don't end up with a
const'ified result.
This is similar to libc's strstr() which also takes a const string but
returns a non-const one.
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
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The structure of the source tree is basically correct and this is
about as far as we can go without hacking at the C code.
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This commit is a first attempt to isolate the udev code from the
remaining code base. It intentionally does not modify any files
but purely delete files which, on a first examination, appear to
not be needed. This is a sweeping commit which may easily have
missed needed code. Files can be retrieved by doing a checkout
from the previous commit:
git checkout 2944f347d0 -- <filename>
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Draw trees more similar to pstree/findmnt/lsblk/...
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When printing cgroup and sysfs hierarchies, avoid using UTF-8 box drawing
characters if the locale is not UTF-8.
https://bugzilla.redhat.com/show_bug.cgi?id=871153
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journalctl and vconsole-setup both implement utf8 locale detection.
Let's have a common function for it.
The next patch will add another use.
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The behaviour of the common name##_from_string conversion is surprising.
It accepts not only the strings from name##_table but also any number
that falls within the range of the table. The order of items in most of
our tables is an internal affair. It should not be visible to the user.
I know of a case where the surprising numeric conversion leads to a crash.
We will allow the direct numeric conversion only for the tables where the
mapping of strings to numeric values has an external meaning. This holds
for the following lookup tables:
- netlink_family, ioprio_class, ip_tos, sched_policy - their numeric
values are stable as they are defined by the Linux kernel interface.
- log_level, log_facility_unshifted - the well-known syslog interface.
We allow the user to use numeric values whose string names systemd does
not know. For instance, the user may want to test a new kernel featuring
a scheduling policy that did not exist when his systemd version was
released. A slightly unpleasant effect of this is that the
name##_to_string conversion cannot return pointers to constant strings
anymore. The strings have to be allocated on demand and freed by the
caller.
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This requires a little bit of tip-toeing around to explicitly avoid
touching the environment from a sig handler. Instead, simply create a
function to reset the var to its "unset" state, allowing the next call
to columns() to recalculate and cache the new value.
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https://bugzilla.redhat.com/show_bug.cgi?id=858777
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Make sure to allocate enough space for readdir_r().
https://bugzilla.redhat.com/show_bug.cgi?id=858754
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- Make writing/reading of /etc/timezone dependendent of HAVE_SYSV_COMPAT
- Introduce symlink_atomic() after all, and use it
- Use relative symlink for /etc/localtime
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Just trying to get the feel for it. And it's pretty cool.
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and make use of it
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#pragma once has been "un-deprecated" in gcc since 3.3, and is widely supported
in other compilers.
I've been using and maintaining (rebasing) this patch for a while now, as
it annoyed me to see #ifndef fooblahfoo, etc all over the place,
almost arrogant about the annoyance of having to define all these names to
perform a commen but neccicary functionality, when a completely superior
alternative exists.
I havn't sent it till now, cause its kindof a style change, and it is bad
voodoo to mess with style that has been established by more established
editors. So feel free to lambast me as a crazy bafoon.
v2 - preserve externally used headers
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This is to match strappend() and the other string related functions.
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