On Mon, Dec 6, 2010 at 3:15 PM, Daniel Becroft <djcbecr...@gmail.com> wrote: > On Mon, Dec 6, 2010 at 8:50 PM, Daniel Becroft <djcbecr...@gmail.com> wrote: > >> On Mon, Dec 6, 2010 at 7:13 PM, Daniel Shahaf <d...@daniel.shahaf.name>wrote: >> >>> Instead of guessing which function causes the lstat() calls, could we >>> have a tool tell? >>> >>> I've looked at 'ltrace -S', but it seems to me that will only tell us >>> which public svn_wc_* API is responsible for the calls. Perhaps there >>> is another tool that can help us follow the entire call chain down to >>> the lstat() call? >>> >>> Daniel >>> . o O (gdb with a breakpoint in lstat() and some fu to extract >>> statistics about the stack trace?) >>> >> >> Very true. >> >> Okay, after a crash course in using GDB, I've run some further testing. >> Running with breakpoints set on the lstat() system call, it looks to be the >> known issue that was originally pointed to. A partial stack trace is below: >> >> #0 0x00007ffff644ab45 in __lxstat (vers=<value optimised out>, >> name=<value optimised out>, buf=0x7fffffffcbf0) >> at ../sysdeps/unix/sysv/linux/wordsize-64/lxstat.c:38 >> #1 0x00007ffff69269b6 in lstat (finfo=0x7fffffffccf0, >> fname=0x6bd638 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> wanted=33137, pool=0x6bd588) at /usr/include/sys/stat.h:464 >> #2 apr_stat (finfo=0x7fffffffccf0, >> fname=0x6bd638 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> wanted=33137, pool=0x6bd588) at file_io/unix/filestat.c:292 >> #3 0x00007ffff6fb1199 in io_check_path ( >> path=0x6bd608 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> resolve_symlinks=0, is_special_p=0x7fffffffced8, kind=0x7fffffffcedc, >> pool=0x6bd588) at subversion/libsvn_subr/io.c:222 >> #4 0x00007ffff6fb1346 in svn_io_check_special_path ( >> path=0x6bd608 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> kind=0x7fffffffcedc, is_special=0x7fffffffced8, pool=0x6bd588) >> at subversion/libsvn_subr/io.c:283 >> #5 0x00007ffff794513d in svn_wc__db_pdh_parse_local_abspath ( >> pdh=0x7fffffffd038, local_relpath=0x7fffffffd030, db=0x64ad38, >> local_abspath=0x6bd608 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> smode=svn_sqlite__mode_readwrite, result_pool=0x6bd588, >> scratch_pool=0x6bd588) at subversion/libsvn_wc/wc_db_pdh.c:382 >> #6 0x00007ffff7935d58 in svn_wc__db_read_info (status=0x7fffffffd184, >> kind=0x7fffffffd188, revision=0x0, repos_relpath=0x0, >> repos_root_url=0x0, >> repos_uuid=0x0, changed_rev=0x0, changed_date=0x0, changed_author=0x0, >> last_mod_time=0x0, depth=0x0, checksum=0x0, translated_size=0x0, >> target=0x0, changelist=0x0, original_repos_relpath=0x0, >> original_root_url=0x0, original_uuid=0x0, original_revision=0x0, >> props_mod=0x0, have_base=0x0, have_work=0x0, conflicted=0x0, lock=0x0, >> db=0x64ad38, >> local_abspath=0x6bd608 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> result_pool=0x6bd588, scratch_pool=0x6bd588) >> at subversion/libsvn_wc/wc_db.c:5261 >> >> However, I then put the breakpont in the svn_wc__db_read_info function and, >> just for A/beta.txt, it gets called 7 times, when in terms leads to 7 >> additional lstat() calls. Looking further the call stack appears as follows: >> >> #0 svn_wc__db_read_info (status=0x7fffffffd184, kind=0x7fffffffd188, >> revision=0x0, repos_relpath=0x0, repos_root_url=0x0, repos_uuid=0x0, >> changed_rev=0x0, changed_date=0x0, changed_author=0x0, >> last_mod_time=0x0, >> depth=0x0, checksum=0x0, translated_size=0x0, target=0x0, >> changelist=0x0, >> original_repos_relpath=0x0, original_root_url=0x0, original_uuid=0x0, >> original_revision=0x0, props_mod=0x0, have_base=0x0, have_work=0x0, >> conflicted=0x0, lock=0x0, db=0x64ad38, >> local_abspath=0x6bd608 "/home/djcbecroft/dev/workingcopy/A/beta.txt", >> result_pool=0x6bd588, scratch_pool=0x6bd588) >> at subversion/libsvn_wc/wc_db.c:5259 >> #1 0x00007ffff78fab96 in walker_helper (db=0x64ad38, >> dir_abspath=0x6ba288 "/home/djcbecroft/dev/workingcopy/A", >> show_hidden=1, >> walk_callback=0x7ffff7ba9026 <get_mergeinfo_walk_cb>, >> walk_baton=0x7fffffffd4e0, depth=svn_depth_infinity, >> cancel_func=0x4119c3 <svn_cl__check_cancel>, cancel_baton=0x0, >> scratch_pool=0x6ba208) at subversion/libsvn_wc/node.c:679 >> #2 0x00007ffff78facb5 in walker_helper (db=0x64ad38, >> dir_abspath=0x67d258 "/home/djcbecroft/dev/workingcopy", show_hidden=1, >> >> walk_callback=0x7ffff7ba9026 <get_mergeinfo_walk_cb>, >> walk_baton=0x7fffffffd4e0, depth=svn_depth_infinity, >> cancel_func=0x4119c3 <svn_cl__check_cancel>, cancel_baton=0x0, >> scratch_pool=0x6a0dc8) at subversion/libsvn_wc/node.c:716 >> #3 0x00007ffff78faf9a in svn_wc__internal_walk_children (db=0x64ad38, >> local_abspath=0x67d258 "/home/djcbecroft/dev/workingcopy", >> show_hidden=1, >> walk_callback=0x7ffff7ba9026 <get_mergeinfo_walk_cb>, >> walk_baton=0x7fffffffd4e0, walk_depth=svn_depth_infinity, >> cancel_func=0x4119c3 <svn_cl__check_cancel>, cancel_baton=0x0, >> scratch_pool=0x6a0dc8) at subversion/libsvn_wc/node.c:763 >> #4 0x00007ffff78fb06d in svn_wc__node_walk_children (wc_ctx=0x64ad20, >> local_abspath=0x67d258 "/home/djcbecroft/dev/workingcopy", >> show_hidden=1, >> walk_callback=0x7ffff7ba9026 <get_mergeinfo_walk_cb>, >> walk_baton=0x7fffffffd4e0, walk_depth=svn_depth_infinity, >> cancel_func=0x4119c3 <svn_cl__check_cancel>, cancel_baton=0x0, >> scratch_pool=0x6a0dc8) at subversion/libsvn_wc/node.c:785 >> >> Using additional breakpoints, I have verified that >> svn_wc__node_walk_children, svn_wc__internal_walk_children and walker_helper >> only get called once. It seems to be an issue within the walker_helper >> itself. >> >> I'll continue looking at it further - let me know if I'm barking up the >> wrong tree. >> >> Cheers, >> Daniel B. >> ... who now has a much greater appreciation for those that debug in GDB on >> a regular basis. >> > > I think I've found the culprit. As we are walking the children > (svn_wc__internal_walk_children, node.c), we call the walk_callback for each > node. At the moment, this is the get_mergeinfo_walk_cb function in merge.c. > Inside this, we call the following: > > svn_wc__node_is_status_present > svn_wc__node_is_status_deleted > svn_wc__node_is_status_absent > svn_wc__path_switched > svn_wc_read_kind > svn_wc__node_get_depth > > Each of these will run a separate svn_wc__db_read_info call, and therefore a > separate lstat(). There's also a couple of other calls that might call it > indirectly.
So it looks an improvement would be something like svn_wc__get_info_for_merge_callback() which does it all in one go (or some other less-verbosely-named function). -Hyrum
