summaryrefslogtreecommitdiff
path: root/src/shared/hashmap.h
AgeCommit message (Collapse)Author
2015-06-11build-sys: split internal basic/ library from shared/Kay Sievers
basic/ can be used by everything cannot use anything outside of basic/ libsystemd/ can use basic/ cannot use shared/ shared/ can use libsystemd/
2015-04-11hashmap: return NULL from destructorDavid Herrmann
We _always_ return NULL from destructors to allow direct assignments to the variable holding the object. Especially on hashmaps, which treat NULL as empty hashmap, this is pretty neat.
2014-12-13configure.ac: add a generic --enable-debug, replace --enable-hashmap-debugMichal Schmidt
There will be more debugging options later. --enable-debug will enable them all. --enable-debug=hashmap will enable only hashmap debugging. Also rename the C #define to ENABLE_DEBUG_* pattern.
2014-12-13shared/hashmap.h: fix commentMichal Schmidt
An early version used underscore prefixes for internal functions, but the current version uses the prefix "internal_".
2014-10-30hashmap: rewrite the implementationMichal Schmidt
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 %
2014-10-23hashmap: allow hashmap_move() to failMichal Schmidt
It cannot fail in the current hashmap implementation, but it may fail in alternative implementations (unless a sufficiently large reservation has been placed beforehand).
2014-10-23hashmap: introduce hashmap_reserve()Michal Schmidt
With the current hashmap implementation that uses chaining, placing a reservation can serve two purposes: - To optimize putting of entries if the number of entries to put is known. The reservation allocates buckets, so later resizing can be avoided. - To avoid having very long bucket chains after using hashmap_move(_one). In an alternative hashmap implementation it will serve an additional purpose: - To guarantee a subsequent hashmap_move(_one) will not fail with -ENOMEM (this never happens in the current implementation).
2014-10-23hashmap: add OrderedHashmap as a distinct typeMichal Schmidt
Few Hashmaps/Sets need to remember the insertion order. Most don't care about the order when iterating. It would be possible to use more compact hashmap storage in the latter cases. Add OrderedHashmap as a distinct type from Hashmap, with functions prefixed with "ordered_". For now, the functions are nothing more than inline wrappers for plain Hashmap functions.
2014-09-15hashmap, set: remove unused functionsMichal Schmidt
The following hashmap_* and set_* functions/macros have never had any users in systemd's history: *_iterate_backwards *_iterate_skip *_last *_FOREACH_BACKWARDS Remove this dead code.
2014-09-15hashmap: introduce hash_ops to make struct Hashmap smallerMichal Schmidt
It is redundant to store 'hash' and 'compare' function pointers in struct Hashmap separately. The functions always comprise a pair. Store a single pointer to struct hash_ops instead. systemd keeps hundreds of hashmaps, so this saves a little bit of memory.
2014-08-19hashmap: try to use the existing 64bit hash functions for dev_t if it is 64bitLennart Poettering
2014-05-15hashmap: add hashmap_remove2() to remove item from hashtable and return both ↵Lennart Poettering
value and key
2013-12-22shared: switch our hash table implementation over to SipHashLennart Poettering
SipHash appears to be the new gold standard for hashing smaller strings for hashtables these days, so let's make use of it.
2013-12-18busctl: output a single sorted list of names, including activatable and ↵Lennart Poettering
activated
2013-10-01hashmap: size hashmap bucket array dynamicallyLennart Poettering
Instead of fixing the hashmap bucket array to 127 entries dynamically size it, starting with a smaller one of 31. As soon as a fill level of 75% is reached, quadruple the size, and so on. This should siginficantly optimize the lookup time in large tables (from O(n) back to O(1)), and save memory on smaller tables (which most are).
2013-05-07hashmap: document trivial_hash_func()Lennart Poettering
2013-05-02Add __attribute__((const, pure, format)) in various placesZbigniew Jędrzejewski-Szmek
I'm assuming that it's fine if a _const_ or _pure_ function calls assert. It is assumed that the assert won't trigger, and even if it does, it can only trigger on the first call with a given set of parameters, and we don't care if the compiler moves the order of calls.
2013-05-03hashmap.h: fix coding style issueDaniel Buch
2013-02-11binfmt,tmpfiles,modules-load,sysctl: rework the various early-boot services ↵Lennart Poettering
that work on .d/ directories This unifies much of the logic behind them: - All four will now ofllow the rule that the earlier file and earlier assignment in the .d/ directories wins. Before, sysctl was the only outlier, where the later setting always won. - All four now support getopt() and --help on the command line. - All four can now handle specification of configuration file names on the command line to apply. The tools will automatically find them, and apply them. Previously only tmpfiles could do that. This is useful for %post scripts in RPMs and suchlike. - This fixes various error path issues in conf_files_list()
2012-10-26journal: introduce entry array chain cacheLennart Poettering
When traversing entry array chains for a bisection or for retrieving an item by index we previously always started at the beginning of the chain. Since we tend to look at the same chains repeatedly, let's cache where we have been the last time, and maybe we can skip ahead with this the next time. This turns most bisections and index lookups from O(log(n)*log(n)) into O(log(n)). More importantly however, we seek around on disk much less, which is good to reduce buffer cache and seek times on rotational disks.
2012-10-25journal: properly serialize fields with multiple values into JSONLennart Poettering
This now matches the JSON serialization spec from: http://www.freedesktop.org/wiki/Software/systemd/json
2012-10-18journal: add ability to list values a specified field can take in all ↵Lennart Poettering
entries of the journal The new 'unique' API allows listing all unique field values that a field specified by a field name can take in all entries of the journal. This allows answering queries such as "What units logged to the journal?", "What hosts have logged into the journal?", "Which boot IDs have logged into the journal?". Ultimately this allows implementation of tools similar to lastlog based on journal data. Note that listing these field values will not work for journal files created with older journald, as the field values are not indexed in older files.
2012-08-14service: add options RestartPreventExitStatus and SuccessExitStatusLukas Nykryn
In some cases, like wrong configuration, restarting after error does not help, so administrator can specify statuses by RestartPreventExitStatus which will not cause restart of a service. Sometimes you have non-standart exit status, so this can be specified by SuccessfulExitStatus.
2012-07-19use #pragma once instead of foo*foo #define guardsShawn Landden
#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
2012-07-03load-fragment: a few modernizationsLennart Poettering
2012-04-12relicense to LGPLv2.1 (with exceptions)Lennart Poettering
We finally got the OK from all contributors with non-trivial commits to relicense systemd from GPL2+ to LGPL2.1+. Some udev bits continue to be GPL2+ for now, but we are looking into relicensing them too, to allow free copy/paste of all code within systemd. The bits that used to be MIT continue to be MIT. The big benefit of the relicensing is that closed source code may now link against libsystemd-login.so and friends.
2012-04-10util: move all to shared/ and split external dependencies in separate ↵Kay Sievers
internal libraries Before: $ ldd /lib/systemd/systemd-timestamp linux-vdso.so.1 => (0x00007fffb05ff000) libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f90aac57000) libcap.so.2 => /lib64/libcap.so.2 (0x00007f90aaa53000) librt.so.1 => /lib64/librt.so.1 (0x00007f90aa84a000) libc.so.6 => /lib64/libc.so.6 (0x00007f90aa494000) /lib64/ld-linux-x86-64.so.2 (0x00007f90aae90000) libdl.so.2 => /lib64/libdl.so.2 (0x00007f90aa290000) libattr.so.1 => /lib64/libattr.so.1 (0x00007f90aa08a000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f90a9e6e000) After: $ ldd systemd-timestamp linux-vdso.so.1 => (0x00007fff3cbff000) libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f5eaa1c3000) librt.so.1 => /lib64/librt.so.1 (0x00007f5ea9fbb000) libc.so.6 => /lib64/libc.so.6 (0x00007f5ea9c04000) /lib64/ld-linux-x86-64.so.2 (0x00007f5eaa3fc000) libdl.so.2 => /lib64/libdl.so.2 (0x00007f5ea9a00000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f5ea97e4000)