# [PATCH] fast-import: Don't count delta attempts against an empty buffer 4 messages from 2018-06-30 to 2018-07-06. Participants: Mike Hommey, Junio C Hamano. Thread: https://gitlist.dev/t/48809 ## Mike Hommey, 2018-06-30 21:41 Subject: [PATCH] fast-import: Don't count delta attempts against an empty buffer Message-ID: <20180630214106.19848-1-mh@glandium.org> URL: https://gitlist.dev/e/20180630214106.19848-1-mh%40glandium.org ``` When the reference buffer is empty, diff_delta returns NULL without really attempting anything, yet fast-import counts that as a delta attempt. Signed-off-by: Mike Hommey --- fast-import.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fast-import.c b/fast-import.c index 4d55910ab9..12195d54d7 100644 --- a/fast-import.c +++ b/fast-import.c @@ -1076,7 +1076,7 @@ static int store_object( return 1; } - if (last && last->data.buf && last->depth < max_depth + if (last && last->data.len && last->data.buf && last->depth < max_depth && dat->len > the_hash_algo->rawsz) { delta_count_attempts_by_type[type]++; -- 2.18.0 ``` ## Junio C Hamano, 2018-07-03 18:41 Subject: Re: [PATCH] fast-import: Don't count delta attempts against an empty buffer Message-ID: URL: https://gitlist.dev/e/xmqqmuv8qhzt.fsf%40gitster-ct.c.googlers.com In-Reply-To: <20180630214106.19848-1-mh@glandium.org> ``` Mike Hommey writes: > When the reference buffer is empty, diff_delta returns NULL without > really attempting anything, yet fast-import counts that as a delta > attempt. But that is an attempt nevertheless, no? Attempted and failed to find anything useful, that is. What problem are you trying to solve and what issue are you trying to address, exactly? ... goes and reads the patch ... > Signed-off-by: Mike Hommey > --- > fast-import.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fast-import.c b/fast-import.c > index 4d55910ab9..12195d54d7 100644 > --- a/fast-import.c > +++ b/fast-import.c > @@ -1076,7 +1076,7 @@ static int store_object( > return 1; > } > > - if (last && last->data.buf && last->depth < max_depth > + if (last && last->data.len && last->data.buf && last->depth < max_depth > && dat->len > the_hash_algo->rawsz) { > > delta_count_attempts_by_type[type]++; This is a misleading patch as the title and the proposed log message both talk about "attempts are counted but we didn't actually do anything", implying that the only problem is that the counter is not aligned with reality. The fact that the post-context we see here only shows the "counting" part does not help us, either. But the next line in the post-context is actually code that does something important, which is ... delta = diff_delta(last->data.buf, last->data.len, dat->buf, dat->len, &deltalen, dat->len - the_hash_algo->rawsz); } else delta = NULL; ... and makes the reader realize that the change itself is much better than the patch with 3-line context, the title, and the proposed log message advertises it as ;-) How about selling it this way instead? fast-import: do not call diff_delta() with empty buffer We know diff_delta() returns NULL, saying "no good delta exists for it", when fed an empty data. Check the length of the data in the caller to avoid such a call. This incidentally reduces the number of attempted deltification we see in the final statistics. or something like that? ``` ## Mike Hommey, 2018-07-03 21:59 Subject: Re: [PATCH] fast-import: Don't count delta attempts against an empty buffer Message-ID: <20180703215920.wjzhhp5yn3mt6rqw@glandium.org> URL: https://gitlist.dev/e/20180703215920.wjzhhp5yn3mt6rqw%40glandium.org In-Reply-To: ``` On Tue, Jul 03, 2018 at 11:41:42AM -0700, Junio C Hamano wrote: > Mike Hommey writes: > > > When the reference buffer is empty, diff_delta returns NULL without > > really attempting anything, yet fast-import counts that as a delta > > attempt. > > But that is an attempt nevertheless, no? Attempted and failed to > find anything useful, that is. What problem are you trying to solve > and what issue are you trying to address, exactly? > > ... goes and reads the patch ... > > > Signed-off-by: Mike Hommey > > --- > > fast-import.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fast-import.c b/fast-import.c > > index 4d55910ab9..12195d54d7 100644 > > --- a/fast-import.c > > +++ b/fast-import.c > > @@ -1076,7 +1076,7 @@ static int store_object( > > return 1; > > } > > > > - if (last && last->data.buf && last->depth < max_depth > > + if (last && last->data.len && last->data.buf && last->depth < max_depth > > && dat->len > the_hash_algo->rawsz) { > > > > delta_count_attempts_by_type[type]++; > > This is a misleading patch as the title and the proposed log message > both talk about "attempts are counted but we didn't actually do > anything", implying that the only problem is that the counter is not > aligned with reality. The fact that the post-context we see here > only shows the "counting" part does not help us, either. > > But the next line in the post-context is actually code that does > something important, which is ... > > delta = diff_delta(last->data.buf, last->data.len, > dat->buf, dat->len, > &deltalen, dat->len - the_hash_algo->rawsz); > } else > delta = NULL; > > > ... and makes the reader realize that the change itself is much > better than the patch with 3-line context, the title, and the > proposed log message advertises it as ;-) > > How about selling it this way instead? > > fast-import: do not call diff_delta() with empty buffer > > We know diff_delta() returns NULL, saying "no good delta > exists for it", when fed an empty data. Check the length of > the data in the caller to avoid such a call. > > This incidentally reduces the number of attempted deltification > we see in the final statistics. > > or something like that? Fair enough. Do you want me to send a v2 with this description? Mike ``` ## Junio C Hamano, 2018-07-06 16:45 Subject: Re: [PATCH] fast-import: Don't count delta attempts against an empty buffer Message-ID: URL: https://gitlist.dev/e/xmqqlgaomhy2.fsf%40gitster-ct.c.googlers.com In-Reply-To: <20180703215920.wjzhhp5yn3mt6rqw@glandium.org> ``` Mike Hommey writes: > On Tue, Jul 03, 2018 at 11:41:42AM -0700, Junio C Hamano wrote: >> Mike Hommey writes: >> >> > When the reference buffer is empty, diff_delta returns NULL without >> > really attempting anything, yet fast-import counts that as a delta >> > attempt. >> >> But that is an attempt nevertheless, no? Attempted and failed to >> find anything useful, that is. What problem are you trying to solve >> and what issue are you trying to address, exactly? >> >> ... goes and reads the patch ... >> >> > Signed-off-by: Mike Hommey >> > --- >> > fast-import.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/fast-import.c b/fast-import.c >> > index 4d55910ab9..12195d54d7 100644 >> > --- a/fast-import.c >> > +++ b/fast-import.c >> > @@ -1076,7 +1076,7 @@ static int store_object( >> > return 1; >> > } >> > >> > - if (last && last->data.buf && last->depth < max_depth >> > + if (last && last->data.len && last->data.buf && last->depth < max_depth >> > && dat->len > the_hash_algo->rawsz) { >> > >> > delta_count_attempts_by_type[type]++; >> >> This is a misleading patch as the title and the proposed log message >> both talk about "attempts are counted but we didn't actually do >> anything", implying that the only problem is that the counter is not >> aligned with reality. The fact that the post-context we see here >> only shows the "counting" part does not help us, either. >> >> But the next line in the post-context is actually code that does >> something important, which is ... >> >> delta = diff_delta(last->data.buf, last->data.len, >> dat->buf, dat->len, >> &deltalen, dat->len - the_hash_algo->rawsz); >> } else >> delta = NULL; >> >> >> ... and makes the reader realize that the change itself is much >> better than the patch with 3-line context, the title, and the >> proposed log message advertises it as ;-) >> >> How about selling it this way instead? >> >> fast-import: do not call diff_delta() with empty buffer >> >> We know diff_delta() returns NULL, saying "no good delta >> exists for it", when fed an empty data. Check the length of >> the data in the caller to avoid such a call. >> >> This incidentally reduces the number of attempted deltification >> we see in the final statistics. >> >> or something like that? > > Fair enough. Do you want me to send a v2 with this description? For a single-patch topic like this one, if you like what was in the e-mail verbatim, saying so is sufficient, as I can just use the material to run "git commit --amend". For anything more involved (e.g. "oh, then insert a code to do this before that function" and/or a fix to an earlier patch in a multi-patch series), I'd prefer a re-submission, which can be processed just the same way as any other new topic. Thanks. ```