some few more 'git checkout' improvements

PATCH In review Kjetil Barvik 3 participants 11 messages Jun 15, 2016 Kbuild

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Kjetil Barvik

author

2016-06-15 22:46 UTC #0 lore raw

cover some few more 'git checkout' improvements

- one bugfix (I hope)
- and one patch to make life easier when using the USE_NSEC define

These 2 patches is based on 'next' because patch 2/2 is based on one previous patch, which is only in 'next' for the moment.

Kjetil Barvik (2):
stat_tracking_info(): only count real commits better introduction of GIT with USE_NSEC defined

 read-cache.c   |   23 +----------------------
 remote.c       |    3 ++-
 unpack-trees.c |    2 --
 3 files changed, 3 insertions(+), 25 deletions(-)

Kjetil Barvik

author

2016-06-15 22:46 UTC #1 lore raw

PATCH 1/2 stat_tracking_info(): only count real commits

stat_tracking_info() in remote.c is used to collect the statistics to be able to say (for instance) from the output of "git checkout':

Your branch and 'foo' have diverged,
and have X and Y different commit(s) each, respectively.

Currently X and Y also includes the count of merges. This patch excludes the merges from being counted.

Signed-off-by Kjetil Barvik <[email protected]>

---

I hope this is a correct fix, and that it is realy a bugfix.

By the way, I have noticed that when the Y number above is large (for instance for a branch I have where Y is ~ 600), then the function get_merge_bases_many() and in particular merge_bases_many() in commit.c will take a noticable amount of user time (aprox 0.4 seconds). So if the chekcout results in that few files need to be updated (< 10), this will sometimes acount for much of the total time needed for the 'git checkout' command.

It seems that even though only max 4000 or so unique commits is touched (when Y ~ 600), each commit is touched over 250 times, for instancce by the insert_by_date() function inside the while-loop in merge_bases_many().

Do someone think it is possible to have a better algorithm here? Maybe O(Nlog(n)) or better? Does someone has a hint about how to make it better?

 remote.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

remote.c +2 -1

index d7079c6..06c414e 100644
@@ -1310,9 +1310,10 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	if (theirs == ours)
 		return 0;
 
-	/* Run "rev-list --left-right ours...theirs" internally... */
+	/* Run "rev-list --no-merges --left-right ours...theirs" internally... */
 	rev_argc = 0;
 	rev_argv[rev_argc++] = NULL;
+	rev_argv[rev_argc++] = "--no-merges";
 	rev_argv[rev_argc++] = "--left-right";
 	rev_argv[rev_argc++] = symmetric;
 	rev_argv[rev_argc++] = "--";

Signature · 1 line

1.6.1.GIT

Kjetil Barvik

author

2016-06-15 22:46 UTC #2 lore raw

PATCH 2/2 better introduction of GIT with USE_NSEC defined

In reply to Kjetil Barvik

Change the source code such that when USE_NSEC is not defined, possible nanosecond timestamps will still be saved in the index file, but not used inside if-test's, and will therefore not affect the outcome of GIT commands, other than the saved nanosecond timestamps in the index file.

This will make it easier to use a system with 2 versions of GIT, one with and one without USE_NSEC defined.

Signed-off-by Kjetil Barvik <[email protected]>

---
 read-cache.c   |   23 +----------------------
 unpack-trees.c |    2 --
 2 files changed, 1 insertions(+), 24 deletions(-)

read-cache.c +1 ~~-22~~

index 91f1d03..7fca804 100644
@@ -69,13 +69,8 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 {
 	ce->ce_ctime.sec = (unsigned int)st->st_ctime;
 	ce->ce_mtime.sec = (unsigned int)st->st_mtime;
-#ifdef USE_NSEC
 	ce->ce_ctime.nsec = (unsigned int)st->st_ctim.tv_nsec;
 	ce->ce_mtime.nsec = (unsigned int)st->st_mtim.tv_nsec;
-#else
-	ce->ce_ctime.nsec = 0;
-	ce->ce_mtime.nsec = 0;
-#endif
 	ce->ce_dev = st->st_dev;
 	ce->ce_ino = st->st_ino;
 	ce->ce_uid = st->st_uid;

@@ -1183,13 +1178,8 @@ static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_en
 
 	ce->ce_ctime.sec = ntohl(ondisk->ctime.sec);
 	ce->ce_mtime.sec = ntohl(ondisk->mtime.sec);
-#ifdef USE_NSEC
 	ce->ce_ctime.nsec = ntohl(ondisk->ctime.nsec);
 	ce->ce_mtime.nsec = ntohl(ondisk->mtime.nsec);
-#else
-	ce->ce_ctime.nsec = 0;
-	ce->ce_mtime.nsec = 0;
-#endif
 	ce->ce_dev   = ntohl(ondisk->dev);
 	ce->ce_ino   = ntohl(ondisk->ino);
 	ce->ce_mode  = ntohl(ondisk->mode);

@@ -1308,12 +1298,8 @@ int read_index_from(struct index_state *istate, const char *path)
 		src_offset += ondisk_ce_size(ce);
 		dst_offset += ce_size(ce);
 	}
-	istate->timestamp.sec = st.st_mtime;
-#ifdef USE_NSEC
+	istate->timestamp.sec = (unsigned int)st.st_mtime;
 	istate->timestamp.nsec = (unsigned int)st.st_mtim.tv_nsec;
-#else
-	istate->timestamp.nsec = 0;
-#endif
 
 	while (src_offset <= mmap_size - 20 - 8) {
 		/* After an array of active_nr index entries,

@@ -1500,13 +1486,8 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
 
 	ondisk->ctime.sec = htonl(ce->ce_ctime.sec);
 	ondisk->mtime.sec = htonl(ce->ce_mtime.sec);
-#ifdef USE_NSEC
 	ondisk->ctime.nsec = htonl(ce->ce_ctime.nsec);
 	ondisk->mtime.nsec = htonl(ce->ce_mtime.nsec);
-#else
-	ondisk->ctime.nsec = 0;
-	ondisk->mtime.nsec = 0;
-#endif
 	ondisk->dev  = htonl(ce->ce_dev);
 	ondisk->ino  = htonl(ce->ce_ino);
 	ondisk->mode = htonl(ce->ce_mode);

@@ -1583,9 +1564,7 @@ int write_index(struct index_state *istate, int newfd)
 	if (ce_flush(&c, newfd) || fstat(newfd, &st))
 		return -1;
 	istate->timestamp.sec = (unsigned int)st.st_ctime;
-#ifdef USE_NSEC
 	istate->timestamp.nsec = (unsigned int)st.st_ctim.tv_nsec;
-#endif
 	return 0;
 }

unpack-trees.c +0 -2

index 9fe0cd5..da2e3c0 100644
@@ -362,9 +362,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	o->result.initialized = 1;
 	if (o->src_index) {
 		o->result.timestamp.sec = o->src_index->timestamp.sec;
-#ifdef USE_NSEC
 		o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-#endif
 	}
 	o->merge_size = len;

Signature · 1 line

1.6.1.GIT

Johannes Sixt

2016-06-15 22:46 UTC #3 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

read-cache.c int read_index_from(struct index_state *istate, const char *path) · line 1316

Quoted 7 lines · Kjetil Barvik

read-cache.c +1 -5

-	istate->timestamp.sec = st.st_mtime;
-#ifdef USE_NSEC
+	istate->timestamp.sec = (unsigned int)st.st_mtime;
 	istate->timestamp.nsec = (unsigned int)st.st_mtim.tv_nsec;
-#else
-	istate->timestamp.nsec = 0;
-#endif

Doesn't this break on systems where st_mtime is time_t and st_mtim does not exist?

-- Hannes

Johannes Sixt

2016-06-15 22:46 UTC #4 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 11 lines · Johannes Sixt

Review
Quoted 7 lines · Kjetil Barvik
(quoted diff) +1 -5
-	istate->timestamp.sec = st.st_mtime;
-#ifdef USE_NSEC
+	istate->timestamp.sec = (unsigned int)st.st_mtime;
 	istate->timestamp.nsec = (unsigned int)st.st_mtim.tv_nsec;
-#else
-	istate->timestamp.nsec = 0;
-#endif
Doesn't this break on systems where st_mtime is time_t and st_mtim does not exist?

Yes, it breaks. You can test this on Linux by commenting out these two lines in git-compat-util.h:

git-compat-util.h +2 -2

index dcf4127..ab4b615 100644
@@ -44,8 +44,8 @@
 #define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
 #endif
 #define _ALL_SOURCE 1
-#define _GNU_SOURCE 1
-#define _BSD_SOURCE 1
+/*#define _GNU_SOURCE 1*/
+/*#define _BSD_SOURCE 1*/
 
 #include <unistd.h>
 #include <stdio.h>

The result even passes the test suite (as long as I don't merge kb/checkout-optim, of course).

-- Hannes

Junio C Hamano

2016-06-15 22:46 UTC #5 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 19 lines · Johannes Sixt

Yes, it breaks. You can test this on Linux by commenting out these two lines in git-compat-util.h:

git-compat-util.h +2 -2

index dcf4127..ab4b615 100644
@@ -44,8 +44,8 @@
 #define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
 #endif
 #define _ALL_SOURCE 1
-#define _GNU_SOURCE 1
-#define _BSD_SOURCE 1
+/*#define _GNU_SOURCE 1*/
+/*#define _BSD_SOURCE 1*/
 
 #include <unistd.h>
 #include <stdio.h>

Quoted 2 lines

The result even passes the test suite (as long as I don't merge kb/checkout-optim, of course).

Isn't it better to separate "do we want to use that information if we can nanosecocond timestamps" and "is the API available for reading nanosecond timestamps" into separete switches, like this partial patch on top of the patch we are discussing, then? It is partial because it shows the way to convert only one call site as an example and of course you need to update the Makefile and autoconf.

git-compat-util.h +8 -0

index 079cbe9..910aa03 100644
@@ -384,4 +384,12 @@ void git_qsort(void *base, size_t nmemb, size_t size,
 # define FORCE_DIR_SET_GID 0
 #endif
 
+#ifdef HAS_NSEC
+#define ST_CTIME_NSEC(st) ((unsigned ing)((st).st_ctim.tv_nsec))
+#define ST_MTIME_NSEC(st) ((unsigned ing)((st).st_mtim.tv_nsec))
+#else
+#define ST_CTIME_NSEC(st) 0
+#define ST_MTIME_NSEC(st) 0
+#endif
+
 #endif

read-cache.c +2 -7

index 91f1d03..bb5cb2b 100644
@@ -69,13 +69,8 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 {
 	ce->ce_ctime.sec = (unsigned int)st->st_ctime;
 	ce->ce_mtime.sec = (unsigned int)st->st_mtime;
-#ifdef USE_NSEC
-	ce->ce_ctime.nsec = (unsigned int)st->st_ctim.tv_nsec;
-	ce->ce_mtime.nsec = (unsigned int)st->st_mtim.tv_nsec;
-#else
-	ce->ce_ctime.nsec = 0;
-	ce->ce_mtime.nsec = 0;
-#endif
+	ce->ce_ctime.nsec = ST_CTIME_NSEC(*st);
+	ce->ce_mtime.nsec = ST_MTIME_NSEC(*st);
 	ce->ce_dev = st->st_dev;
 	ce->ce_ino = st->st_ino;
 	ce->ce_uid = st->st_uid;

Junio C Hamano

2016-06-15 22:46 UTC #6 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 20 lines · Junio C Hamano

Quoted 18 lines · Johannes Sixt
Yes, it breaks. You can test this on Linux by commenting out these two lines in git-compat-util.h:
git-compat-util.h +2 -2
index dcf4127..ab4b615 100644
@@ -44,8 +44,8 @@
 #define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
 #endif
 #define _ALL_SOURCE 1
-#define _GNU_SOURCE 1
-#define _BSD_SOURCE 1
+/*#define _GNU_SOURCE 1*/
+/*#define _BSD_SOURCE 1*/
 #include <unistd.h>
 #include <stdio.h>
 

Quoted 2 lines

Quoted 2 lines
The result even passes the test suite (as long as I don't merge kb/checkout-optim, of course).

This actually will trigger more compilation breakages than that. For example, it hides memmem() and strchrnul() from everybody, and makes the compilation error out with this subtract as the compiler has to assume you are subtracting a pointer from an integer:

		linelen = strchrnul(msg_p, '\n') - msg_p;

I cannot test the result myself to see if it still works this way.

Quoted 6 lines

Isn't it better to separate "do we want to use that information if we can nanosecocond timestamps" and "is the API available for reading nanosecond timestamps" into separete switches, like this partial patch on top of the patch we are discussing, then? It is partial because it shows the way to convert only one call site as an example and of course you need to update the Makefile and autoconf.

And here is what I did. It is meant to replace the patch in discussion.

-- >8 --
Record ns-timestamps if possible, but do not use it without USE_NSEC

Traditionally, the lack of USE_NSEC meant "do not record nor use the nanosecond resolution part of the file timestamps". To avoid problems on filesystems that lose the ns part when the metadata is flushed to the disk and then later read back in, disabling USE_NSEC has been a good idea in general.

If you are on a filesystem without such an issue, it does not hurt to read and store them in the cached stat data in the index entries even if your git is compiled without USE_NSEC. The index left with such a version of git can be read by git compiled with USE_NSEC and it can make use of the nanosecond part to optimize the check to see if the path on the filesystem hsa been modified since we last looked at.

Signed-off-by Junio C Hamano <[email protected]>

---
 Makefile             |    7 +++++++
 builtin-fetch-pack.c |    4 +---
 git-compat-util.h    |    9 +++++++++
 read-cache.c         |   29 ++++-------------------------
 unpack-trees.c       |    2 --
 5 files changed, 21 insertions(+), 30 deletions(-)

Makefile +7 -0

index 27b9569..e63034d 100644
@@ -126,6 +126,9 @@ all::
 # randomly break unless your underlying filesystem supports those sub-second
 # times (my ext3 doesn't).
 #
+# Define NO_NSEC if your "struct stat" does not have "st_ctim.tv_nsec"
+# available.  This automatically turns USE_NSEC off.
+#
 # Define USE_STDEV below if you want git to care about the underlying device
 # change being considered an inode change from the update-index perspective.
 #

@@ -802,6 +805,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	RUNTIME_PREFIX = YesPlease
 	NO_POSIX_ONLY_PROGRAMS = YesPlease
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
+	NO_NSEC = YesPlease
 	COMPAT_CFLAGS += -D__USE_MINGW_ACCESS -DNOGDI -Icompat -Icompat/regex -Icompat/fnmatch
 	COMPAT_CFLAGS += -DSNPRINTF_SIZE_CORR=1
 	COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"

@@ -923,6 +927,9 @@ endif
 ifdef NO_ST_BLOCKS_IN_STRUCT_STAT
 	BASIC_CFLAGS += -DNO_ST_BLOCKS_IN_STRUCT_STAT
 endif
+ifdef NO_NSEC
+	BASIC_CFLAGS += -DNO_NSEC
+endif
 ifdef NO_C99_FORMAT
 	BASIC_CFLAGS += -DNO_C99_FORMAT
 endif

builtin-fetch-pack.c +1 -3

index 3b210c7..59b0b0a 100644
@@ -801,9 +801,7 @@ struct ref *fetch_pack(struct fetch_pack_args *my_args,
 		int fd;
 
 		mtime.sec = st.st_mtime;
-#ifdef USE_NSEC
-		mtime.nsec = st.st_mtim.tv_nsec;
-#endif
+		mtime.nsec = ST_MTIME_NSEC(st);
 		if (stat(shallow, &st)) {
 			if (mtime.sec)
 				die("shallow file was removed during fetch");

git-compat-util.h +9 -0

index 079cbe9..9b495dc 100644
@@ -384,4 +384,13 @@ void git_qsort(void *base, size_t nmemb, size_t size,
 # define FORCE_DIR_SET_GID 0
 #endif
 
+#ifdef NO_NSEC
+#undef USE_NSEC
+#define ST_CTIME_NSEC(st) 0
+#define ST_MTIME_NSEC(st) 0
+#else
+#define ST_CTIME_NSEC(st) ((unsigned int)((st).st_ctim.tv_nsec))
+#define ST_MTIME_NSEC(st) ((unsigned int)((st).st_mtim.tv_nsec))
+#endif
+
 #endif

read-cache.c +4 ~~-25~~

index 91f1d03..b819abb 100644
@@ -69,13 +69,8 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 {
 	ce->ce_ctime.sec = (unsigned int)st->st_ctime;
 	ce->ce_mtime.sec = (unsigned int)st->st_mtime;
-#ifdef USE_NSEC
-	ce->ce_ctime.nsec = (unsigned int)st->st_ctim.tv_nsec;
-	ce->ce_mtime.nsec = (unsigned int)st->st_mtim.tv_nsec;
-#else
-	ce->ce_ctime.nsec = 0;
-	ce->ce_mtime.nsec = 0;
-#endif
+	ce->ce_ctime.nsec = ST_CTIME_NSEC(*st);
+	ce->ce_mtime.nsec = ST_MTIME_NSEC(*st);
 	ce->ce_dev = st->st_dev;
 	ce->ce_ino = st->st_ino;
 	ce->ce_uid = st->st_uid;

@@ -1183,13 +1178,8 @@ static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_en
 
 	ce->ce_ctime.sec = ntohl(ondisk->ctime.sec);
 	ce->ce_mtime.sec = ntohl(ondisk->mtime.sec);
-#ifdef USE_NSEC
 	ce->ce_ctime.nsec = ntohl(ondisk->ctime.nsec);
 	ce->ce_mtime.nsec = ntohl(ondisk->mtime.nsec);
-#else
-	ce->ce_ctime.nsec = 0;
-	ce->ce_mtime.nsec = 0;
-#endif
 	ce->ce_dev   = ntohl(ondisk->dev);
 	ce->ce_ino   = ntohl(ondisk->ino);
 	ce->ce_mode  = ntohl(ondisk->mode);

@@ -1309,11 +1299,7 @@ int read_index_from(struct index_state *istate, const char *path)
 		dst_offset += ce_size(ce);
 	}
 	istate->timestamp.sec = st.st_mtime;
-#ifdef USE_NSEC
-	istate->timestamp.nsec = (unsigned int)st.st_mtim.tv_nsec;
-#else
-	istate->timestamp.nsec = 0;
-#endif
+	istate->timestamp.nsec = ST_MTIME_NSEC(st);
 
 	while (src_offset <= mmap_size - 20 - 8) {
 		/* After an array of active_nr index entries,

@@ -1500,13 +1486,8 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
 
 	ondisk->ctime.sec = htonl(ce->ce_ctime.sec);
 	ondisk->mtime.sec = htonl(ce->ce_mtime.sec);
-#ifdef USE_NSEC
 	ondisk->ctime.nsec = htonl(ce->ce_ctime.nsec);
 	ondisk->mtime.nsec = htonl(ce->ce_mtime.nsec);
-#else
-	ondisk->ctime.nsec = 0;
-	ondisk->mtime.nsec = 0;
-#endif
 	ondisk->dev  = htonl(ce->ce_dev);
 	ondisk->ino  = htonl(ce->ce_ino);
 	ondisk->mode = htonl(ce->ce_mode);

@@ -1583,9 +1564,7 @@ int write_index(struct index_state *istate, int newfd)
 	if (ce_flush(&c, newfd) || fstat(newfd, &st))
 		return -1;
 	istate->timestamp.sec = (unsigned int)st.st_ctime;
-#ifdef USE_NSEC
-	istate->timestamp.nsec = (unsigned int)st.st_ctim.tv_nsec;
-#endif
+	istate->timestamp.nsec = ST_CTIME_NSEC(st);
 	return 0;
 }

unpack-trees.c +0 -2

index 9fe0cd5..da2e3c0 100644
@@ -362,9 +362,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	o->result.initialized = 1;
 	if (o->src_index) {
 		o->result.timestamp.sec = o->src_index->timestamp.sec;
-#ifdef USE_NSEC
 		o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-#endif
 	}
 	o->merge_size = len;

Johannes Sixt

2016-06-15 22:46 UTC #7 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 17 lines · Junio C Hamano

Record ns-timestamps if possible, but do not use it without USE_NSEC
Traditionally, the lack of USE_NSEC meant "do not record nor use the nanosecond resolution part of the file timestamps". To avoid problems on filesystems that lose the ns part when the metadata is flushed to the disk and then later read back in, disabling USE_NSEC has been a good idea in general.
If you are on a filesystem without such an issue, it does not hurt to read and store them in the cached stat data in the index entries even if your git is compiled without USE_NSEC. The index left with such a version of git can be read by git compiled with USE_NSEC and it can make use of the nanosecond part to optimize the check to see if the path on the filesystem hsa been modified since we last looked at.
Signed-off-by Junio C Hamano <[email protected]>
---

...

Quoted 3 lines

(quoted diff) +3 -0

+# Define NO_NSEC if your "struct stat" does not have "st_ctim.tv_nsec"
+# available.  This automatically turns USE_NSEC off.
+#

...

Review ifneq (,$(findstring MINGW,$(uname_S))) · line 811

Quoted 8 lines

(quoted diff) +1 -0

@@ -802,6 +805,7 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	RUNTIME_PREFIX = YesPlease
 	NO_POSIX_ONLY_PROGRAMS = YesPlease
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
+	NO_NSEC = YesPlease
 	COMPAT_CFLAGS += -D__USE_MINGW_ACCESS -DNOGDI -Icompat -Icompat/regex -Icompat/fnmatch
 	COMPAT_CFLAGS += -DSNPRINTF_SIZE_CORR=1
 	COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"

Thanks, with this the build no longer breaks on Windows. But I need this option on AIX as well:

Makefile +1 -0

index 137a3ff..b974978 100644
@@ -737,6 +737,7 @@ ifeq ($(uname_S),AIX)
 	NO_MEMMEM = YesPlease
 	NO_MKDTEMP = YesPlease
 	NO_STRLCPY = YesPlease
+	NO_NSEC = YesPlease
 	FREAD_READS_DIRECTORIES = UnfortunatelyYes
 	INTERNAL_QSORT = UnfortunatelyYes
 	NEEDS_LIBICONV=YesPlease

-- Hannes

Junio C Hamano

2016-06-15 22:46 UTC #8 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

In reply to Kjetil Barvik

Quoted 8 lines · Kjetil Barvik

Change the source code such that when USE_NSEC is not defined, possible nanosecond timestamps will still be saved in the index file, but not used inside if-test's, and will therefore not affect the outcome of GIT commands, other than the saved nanosecond timestamps in the index file.
This will make it easier to use a system with 2 versions of GIT, one with and one without USE_NSEC defined.

I take it that you are responding to my earlier question with this patch?

    From: Junio C Hamano <[email protected]>
    Subject: Re: [PATCH/RFC v2 2/3] make USE_NSEC work as expected
    Date: Fri, 20 Feb 2009 00:35:35 -0800
    Message-ID: <[email protected]>

    Kjetil Barvik <[email protected]> writes:

    > diff --git a/read-cache.c b/read-cache.c
    > index 940ec76..ca4bec2 100644
    > --- a/read-cache.c
    > +++ b/read-cache.c
    > @@ -67,8 +67,15 @@ void rename_index_entry_at(struct index_state *istate,..
    >   */
    >  void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
    >  {
    > -	ce->ce_ctime = st->st_ctime;
    > -	ce->ce_mtime = st->st_mtime;
    > +	ce->ce_ctime.sec = (unsigned int)st->st_ctime;
    > +	ce->ce_mtime.sec = (unsigned int)st->st_mtime;
    > +#ifdef USE_NSEC
    > +	ce->ce_ctime.nsec = (unsigned int)st->st_ctim.tv_nsec;
    > +	ce->ce_mtime.nsec = (unsigned int)st->st_mtim.tv_nsec;
    > +#else
    > +	ce->ce_ctime.nsec = 0;
    > +	ce->ce_mtime.nsec = 0;
    > +#endif

    How does this affect a use case where the same index file used with two 
    instances of git (one compiled with and another without USE_NSEC)?

Kjetil Barvik

author

2016-06-15 22:46 UTC #9 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 8 lines · Junio C Hamano

Quoted 6 lines · Kjetil Barvik
Change the source code such that when USE_NSEC is not defined, possible nanosecond timestamps will still be saved in the index file, but not used inside if-test's, and will therefore not affect the outcome of GIT commands, other than the saved nanosecond timestamps in the index file.

Quoted 5 lines

Quoted 2 lines
This will make it easier to use a system with 2 versions of GIT, one with and one without USE_NSEC defined.
I take it that you are responding to my earlier question with this patch?

Yes, you are correct.

[....]

Quoted 2 lines

How does this affect a use case where the same index file used with two instances of git (one compiled with and another without USE_NSEC)?

If both persons in this use case use this patch, the one with USE_NSEC defined will now be able to take full advantage of the nanosecond timestamps at all times.

The one without USE_NSEC defined should not be able to tell the difference (without looking into to details of the index file).

-- kjetil

Junio C Hamano

2016-06-15 22:46 UTC #10 lore raw

Re: [PATCH 2/2] better introduction of GIT with USE_NSEC defined

Quoted 11 lines · Kjetil Barvik

Junio C Hamano <[email protected]> writes:
...
Quoted 2 lines
How does this affect a use case where the same index file used with two instances of git (one compiled with and another without USE_NSEC)?
If both persons in this use case use this patch, the one with USE_NSEC defined will now be able to take full advantage of the nanosecond timestamps at all times.
The one without USE_NSEC defined should not be able to tell the difference (without looking into to details of the index file).

As long as the implementation does not give false cleanliness it is perfectly fine; false dirtinesss is just a bit of wasted cycle.

Thanks.