@matheusbsbs / matheus-bagliano / commits / 2a9dedef2e

index: make index.threads=true enable ieot and eoie

If a user explicitly sets [index] threads = true to read the index using multiple threads, ensure that index writes include the offset table by default to make that possible. This ensures that the user's intent of turning on threading is respected. In other words, permit the following configurations: - index.threads and index.recordOffsetTable unspecified: do not write the offset table yet (to avoid alarming the user with "ignoring IEOT extension" messages when an older version of Git accesses the repository) but do make use of multiple threads to read the index if the supporting offset table is present. This can also be requested explicitly by setting index.threads=true, 0, or >1 and index.recordOffsetTable=false. - index.threads=false or 1: do not write the offset table, and do not make use of the offset table. One can set index.recordOffsetTable=false as well, to be more explicit. - index.threads=true, 0, or >1 and index.recordOffsetTable unspecified: write the offset table and make use of threads at read time. This can also be requested by setting index.threads=true, 0, >1, or unspecified and index.recordOffsetTable=true. Fortunately the complication is temporary: once most Git installations have upgraded to a version with support for the IEOT and EOIE extensions, we can flip the defaults for index.recordEndOfIndexEntries and index.recordOffsetTable to true and eliminate the settings. Helped-by: Ben Peart <benpeart@microsoft.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jonathan Nieder committed Nov 19, 2018 at 22:14 UTC 2a9dedef2ef76916be4a314a7e739f253eaf05db

4 files changed +32 -16

Documentation/config/index.txt

+4 -2

@@ -3,14 +3,16 @@ index.recordEndOfIndexEntries::

3 Entry" section. This reduces index load time on multiprocessor

4 machines but produces a message "ignoring EOIE extension" when

5 reading the index using Git versions before 2.20. Defaults to

6 - 'false'.

6 + 'true' if index.threads has been explicitly enabled, 'false'

7 + otherwise.

9 index.recordOffsetTable::

10 Specifies whether the index file should include an "Index Entry

11 Offset Table" section. This reduces index load time on

12 multiprocessor machines but produces a message "ignoring IEOT

13 extension" when reading the index using Git versions before 2.20.

13 - Defaults to 'false'.

14 + Defaults to 'true' if index.threads has been explicitly enabled,

15 + 'false' otherwise.

17 index.threads::

18 Specifies the number of threads to spawn when loading the index.

config.c

+10 -7

@@ -2294,22 +2294,25 @@ int git_config_get_fsmonitor(void)

2294 return 0;

2295 }

2296

2297 -int git_config_get_index_threads(void)

2297 +int git_config_get_index_threads(int *dest)

2298 {

2299 - int is_bool, val = 0;

2299 + int is_bool, val;

2300

2301 val = git_env_ulong("GIT_TEST_INDEX_THREADS", 0);

2302 - if (val)

2303 - return val;

2302 + if (val) {

2303 + *dest = val;

2304 + return 0;

2305 + }

2306

2307 if (!git_config_get_bool_or_int("index.threads", &is_bool, &val)) {

2308 if (is_bool)

2307 - return val ? 0 : 1;

2309 + *dest = val ? 0 : 1;

2310 else

2309 - return val;

2311 + *dest = val;

2312 + return 0;

2313 }

2314

2312 - return 0; /* auto */

2315 + return 1;

2316 }

2317

2318 NORETURN

config.h

+1 -1

@@ -246,11 +246,11 @@ extern int git_config_get_bool(const char *key, int *dest);

246 extern int git_config_get_bool_or_int(const char *key, int *is_bool, int *dest);

247 extern int git_config_get_maybe_bool(const char *key, int *dest);

248 extern int git_config_get_pathname(const char *key, const char **dest);

249 +extern int git_config_get_index_threads(int *dest);

250 extern int git_config_get_untracked_cache(void);

251 extern int git_config_get_split_index(void);

252 extern int git_config_get_max_percent_split_change(void);

253 extern int git_config_get_fsmonitor(void);

253 -extern int git_config_get_index_threads(void);

254

255 /* This dies if the configured or default date is in the future */

256 extern int git_config_get_expiry(const char *key, const char **output);

read-cache.c

+17 -6

@@ -2176,7 +2176,8 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)

2176

2177 src_offset = sizeof(*hdr);

2178

2179 - nr_threads = git_config_get_index_threads();

2179 + if (git_config_get_index_threads(&nr_threads))

2180 + nr_threads = 1;

2181

2182 /* TODO: does creating more threads than cores help? */

2183 if (!nr_threads) {

@@ -2695,7 +2696,13 @@ static int record_eoie(void)

2696

2697 if (!git_config_get_bool("index.recordendofindexentries", &val))

2698 return val;

2698 - return 0;

2699 +

2700 + /*

2701 + * As a convenience, the end of index entries extension

2702 + * used for threading is written by default if the user

2703 + * explicitly requested threaded index reads.

2704 + */

2705 + return !git_config_get_index_threads(&val) && val != 1;

2706 }

2707

2708 static int record_ieot(void)

@@ -2704,7 +2711,13 @@ static int record_ieot(void)

2711

2712 if (!git_config_get_bool("index.recordoffsettable", &val))

2713 return val;

2707 - return 0;

2714 +

2715 + /*

2716 + * As a convenience, the offset table used for threading is

2717 + * written by default if the user explicitly requested

2718 + * threaded index reads.

2719 + */

2720 + return !git_config_get_index_threads(&val) && val != 1;

2721 }

2722

2723 /*

@@ -2765,9 +2778,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,

2778 if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)

2779 return -1;

2780

2768 - if (HAVE_THREADS)

2769 - nr_threads = git_config_get_index_threads();

2770 - else

2781 + if (!HAVE_THREADS || git_config_get_index_threads(&nr_threads))

2782 nr_threads = 1;

2783

2784 if (nr_threads != 1 && record_ieot()) {