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From Kyle Leber <kyle.le...@gmail.com>
Subject Re: svn merge operation extremely slow
Date Mon, 03 Oct 2011 00:05:19 GMT
Johan,

I did a little more digging.  There were a few different places where svn
seems to get hung up so I ran the gprof report on just the first one (the
merge takes hours otherwise).  In this particular case, svn prints out that
it is merging from a small text file while it is hanging for more than a
minute @ 100% CPU.  When I examine "lsof", however, it see it actually has a
different file open.  This one is a large (15 MB) "binary" file.  It turns
out this binary file did not have a property in the trunk (which I think
means it's treated as text, right?).  But in the branch it was marked as
octet stream.   So perhaps svn is doing a text-based diff on this binary
file because it used to be incorrectly marked as text?

Side-note: The contents of this 15MB file are actually ASCII, but we do want
it treated as binary b/c line-based merges are never valid.

Another snippet from the same gprof report is below.

Cheers,
Kyle

-----------------------------------------------
                0.00  144.03      27/27          do_text_merge [10]
[11]    95.9    0.00  144.03      27         svn_diff_file_diff3_2 [11]
                0.01  144.02      27/27          svn_diff_diff3_2 [12]
                0.00    0.00      27/5723        apr_pool_destroy [833]
                0.00    0.00      27/6430        svn_pool_create_ex [1558]
-----------------------------------------------
                0.01  144.02      27/27          svn_diff_file_diff3_2 [11]
[12]    95.9    0.01  144.02      27         svn_diff_diff3_2 [12]
                8.64  128.73      54/56          svn_diff(long, char, short)
[13]
                0.01    5.09   21014/21014       svn_diff__resolve_conflict
[15]
                0.03    1.51      81/81          svn_diff__get_tokens [25]
                0.00    0.01      27/27          datasources_open [272]
                0.01    0.00      81/85          svn_diff__get_token_counts
[284]
                0.00    0.00   42065/2476341     apr_palloc [136]
                0.00    0.00      27/27          svn_diff__tree_create
[1235]
                0.00    0.00      54/5723        apr_pool_destroy [833]
                0.00    0.00      27/27          token_discard_all [1282]
                0.00    0.00      54/6430        svn_pool_create_ex [1558]
                0.00    0.00      27/27          svn_diff__get_node_count
[1911]
-----------------------------------------------
                0.32    4.77       2/56          svn_diff__resolve_conflict
[15]
                8.64  128.73      54/56          svn_diff_diff3_2 [12]
[13]    94.8    8.96  133.49      56         svn_diff(long, char, short)
[13]
              133.49    0.00 2002891836/2002891836     svn_diff__snake [14]
                0.00    0.00     224/2476341     apr_palloc [136]
                0.00    0.00      64/64          prepend_lcs [1103]
                0.00    0.00      56/56          svn_diff__lcs_reverse
[1875]
-----------------------------------------------
              133.49    0.00 2002891836/2002891836     svn_diff(long, char,
short) [13]
[14]    88.9  133.49    0.00 2002891836         svn_diff__snake [14]
                0.00    0.00  168906/2476341     apr_palloc [136]

On Sun, Oct 2, 2011 at 5:58 PM, Johan Corveleyn <jcorvel@gmail.com> wrote:

> On Sun, Oct 2, 2011 at 11:08 PM, Kyle Leber <kyle.leber@gmail.com> wrote:
> > I was able to capture a profile from svn (after remembering I have to
> link
> > statically).  I compiled with "-pg -O0" Here is the top of the file:
> >
> > Each sample counts as 0.01 seconds.
> >   %   cumulative   self              self     total
> >  time   seconds   seconds    calls   s/call   s/call  name
> >  88.88    133.49   133.49 2002891836     0.00     0.00  svn_diff__snake
> >   5.97    142.45     8.96       56     0.16     2.54  svn_diff(long,
> char,
> > short)
> >   1.98    145.42     2.97  4163001     0.00     0.00  MD5Transform
> >   0.41    146.04     0.62  4163001     0.00     0.00  Decode
>
> What's it doing in svn_diff__snake (or svn_diff for that matter)? That
> should only be hit when svn is doing textual merges (in which case it
> must do rather expensive diff calculations --- I'm sure those
> calculations can go ballistic when being confronted with a large
> binary file, not consisting of text lines).
>
> Are you sure those files were actually marked as binary (svn:mime-type
> of application/octet-stream or something else non-texty)?
>
> --
> Johan
>

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