git-commit-vandalism/t/helper/test-tool.h
Eric Wong 92d8ed8ac1 oidtree: a crit-bit tree for odb_loose_cache
This saves 8K per `struct object_directory', meaning it saves
around 800MB in my case involving 100K alternates (half or more
of those alternates are unlikely to hold loose objects).

This is implemented in two parts: a generic, allocation-free
`cbtree' and the `oidtree' wrapper on top of it.  The latter
provides allocation using alloc_state as a memory pool to
improve locality and reduce free(3) overhead.

Unlike oid-array, the crit-bit tree does not require sorting.
Performance is bound by the key length, for oidtree that is
fixed at sizeof(struct object_id).  There's no need to have
256 oidtrees to mitigate the O(n log n) overhead like we did
with oid-array.

Being a prefix trie, it is natively suited for expanding short
object IDs via prefix-limited iteration in
`find_short_object_filename'.

On my busy workstation, p4205 performance seems to be roughly
unchanged (+/-8%).  Startup with 100K total alternates with no
loose objects seems around 10-20% faster on a hot cache.
(800MB in memory savings means more memory for the kernel FS
cache).

The generic cbtree implementation does impose some extra
overhead for oidtree in that it uses memcmp(3) on
"struct object_id" so it wastes cycles comparing 12 extra bytes
on SHA-1 repositories.  I've not yet explored reducing this
overhead, but I expect there are many places in our code base
where we'd want to investigate this.

More information on crit-bit trees: https://cr.yp.to/critbit.html

Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-07-07 21:28:04 -07:00

79 lines
3.5 KiB
C

#ifndef TEST_TOOL_H
#define TEST_TOOL_H
#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "git-compat-util.h"
int cmd__advise_if_enabled(int argc, const char **argv);
int cmd__bitmap(int argc, const char **argv);
int cmd__bloom(int argc, const char **argv);
int cmd__chmtime(int argc, const char **argv);
int cmd__config(int argc, const char **argv);
int cmd__crontab(int argc, const char **argv);
int cmd__ctype(int argc, const char **argv);
int cmd__date(int argc, const char **argv);
int cmd__delta(int argc, const char **argv);
int cmd__dir_iterator(int argc, const char **argv);
int cmd__drop_caches(int argc, const char **argv);
int cmd__dump_cache_tree(int argc, const char **argv);
int cmd__dump_fsmonitor(int argc, const char **argv);
int cmd__dump_split_index(int argc, const char **argv);
int cmd__dump_untracked_cache(int argc, const char **argv);
int cmd__example_decorate(int argc, const char **argv);
int cmd__fast_rebase(int argc, const char **argv);
int cmd__genrandom(int argc, const char **argv);
int cmd__genzeros(int argc, const char **argv);
int cmd__hashmap(int argc, const char **argv);
int cmd__hash_speed(int argc, const char **argv);
int cmd__index_version(int argc, const char **argv);
int cmd__json_writer(int argc, const char **argv);
int cmd__lazy_init_name_hash(int argc, const char **argv);
int cmd__match_trees(int argc, const char **argv);
int cmd__mergesort(int argc, const char **argv);
int cmd__mktemp(int argc, const char **argv);
int cmd__oidmap(int argc, const char **argv);
int cmd__oidtree(int argc, const char **argv);
int cmd__online_cpus(int argc, const char **argv);
int cmd__parse_options(int argc, const char **argv);
int cmd__parse_pathspec_file(int argc, const char** argv);
int cmd__path_utils(int argc, const char **argv);
int cmd__pcre2_config(int argc, const char **argv);
int cmd__pkt_line(int argc, const char **argv);
int cmd__prio_queue(int argc, const char **argv);
int cmd__proc_receive(int argc, const char **argv);
int cmd__progress(int argc, const char **argv);
int cmd__reach(int argc, const char **argv);
int cmd__read_cache(int argc, const char **argv);
int cmd__read_graph(int argc, const char **argv);
int cmd__read_midx(int argc, const char **argv);
int cmd__ref_store(int argc, const char **argv);
int cmd__regex(int argc, const char **argv);
int cmd__repository(int argc, const char **argv);
int cmd__revision_walking(int argc, const char **argv);
int cmd__run_command(int argc, const char **argv);
int cmd__scrap_cache_tree(int argc, const char **argv);
int cmd__serve_v2(int argc, const char **argv);
int cmd__sha1(int argc, const char **argv);
int cmd__oid_array(int argc, const char **argv);
int cmd__sha256(int argc, const char **argv);
int cmd__sigchain(int argc, const char **argv);
int cmd__simple_ipc(int argc, const char **argv);
int cmd__strcmp_offset(int argc, const char **argv);
int cmd__string_list(int argc, const char **argv);
int cmd__submodule_config(int argc, const char **argv);
int cmd__submodule_nested_repo_config(int argc, const char **argv);
int cmd__subprocess(int argc, const char **argv);
int cmd__trace2(int argc, const char **argv);
int cmd__userdiff(int argc, const char **argv);
int cmd__urlmatch_normalization(int argc, const char **argv);
int cmd__xml_encode(int argc, const char **argv);
int cmd__wildmatch(int argc, const char **argv);
#ifdef GIT_WINDOWS_NATIVE
int cmd__windows_named_pipe(int argc, const char **argv);
#endif
int cmd__write_cache(int argc, const char **argv);
int cmd_hash_impl(int ac, const char **av, int algo);
#endif