<div dir="ltr"><div dir="ltr">(Resending with history trimmed to avoid it getting stuck in moderator queue).<br></div><div class="gmail_quote"><div dir="ltr" class="gmail_attr"><br></div><div><div>Hi Alexey,</div><div><br></div><div>Just an update - I identified the cause of the "Generated debug info is broken" error message when I tried to build things locally: the `outStreamer` instance is initialised with the host Triple, instead of whatever the target's triple is. For example, I build and run LLD on Windows, which means that a Windows triple will be generated, and consequently a COFF-emitting streamer will be created, rather than the ELF-emitting one I'd expect were the triple information to somehow be derived from the linker flavor/input objects etc. Hard-coding in my target triple resolved the issue (although I still got the other warnings mentioned from my game link).</div><div><br></div><div>I measured the performance figures using LLD patched as described, and using the same methodology as my earlier results, and got the following:</div><br><div>
<div>Link-time speed (s):</div><div><span style="font-family:monospace">+-----------------------------+---------------+</span><br></div><div><font face="monospace">| Package variant | GC 1 (normal) |</font></div><div><font face="monospace">+-----------------------------+---------------+<br></font></div><div><font face="monospace">| Game (DWARF linker) | 53.6 |
</font><div><font face="monospace">| Game (DWARF linker, no ODR) | 63.6 |</font></div>
</div><div><font face="monospace">| Clang (DWARF linker) | 200.6 |</font></div><div><font face="monospace">+-----------------------------+---------------+</font></div><div><font face="monospace"><br></font></div><div><font face="monospace">
</font><div><font face="monospace"><font face="arial,sans-serif">Output size - Game package (MB):</font></font></div><div><font face="monospace"><font face="arial,sans-serif"><span style="font-family:monospace">+-----------------------------+------+</span><br></font></font></div><div><span style="font-family:monospace">| Category | GC 1 |<br></span></div><div><span style="font-family:monospace">+-----------------------------+------+<br></span></div><div><span style="font-family:monospace">| DWARFLinker (total) | 696 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
(DWARF*) | 429 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
(other) | 267 |
</span><div><span style="font-family:monospace">| DWARFLinker no ODR (total) | 753 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
no ODR (DWARF*) | 485 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
no ODR (other) | 268 |</span></div>
</div><div><font face="monospace">+-----------------------------+------+</font><div><font face="monospace"><br></font></div><div><font face="monospace"><font face="arial,sans-serif">Output size - Clang (MB):
</font></font><div><font face="monospace"><font face="arial,sans-serif"><span style="font-family:monospace">+-----------------------------+------+</span><br></font></font></div><div><span style="font-family:monospace">| Category | GC 1 |<br></span></div><div><span style="font-family:monospace">+-----------------------------+------+</span></div>
<div><span style="font-family:monospace">| DWARFLinker (total) | 1294 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
(DWARF*) | 743 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
(other) | 551 |
<span style="font-family:monospace">
</span></span><div><span style="font-family:monospace">| DWARFLinker no ODR (total) | 1294 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
no ODR (DWARF*) | 743 |<br></span></div><div><span style="font-family:monospace">|
DWARFLinker
no ODR (other) | 551 |
</span><div><div><span style="font-family:monospace"></span></div>
</div><div><font face="monospace">+-----------------------------+------+</font></div>
</div></div><div><font face="monospace"><br></font></div><div><font face="monospace"><span style="font-family:arial,sans-serif">*DWARF = just .debug_info, .debug_line, .debug_loc, .debug_aranges, .debug_ranges.</span></font></div><div><font face="monospace"><span style="font-family:arial,sans-serif"></span></font><br><font face="monospace"><span style="font-family:arial,sans-serif"></span>
</font><div><span style="font-family:monospace"><span style="font-family:arial,sans-serif">Peak Working Set Memory usage (GB):</span><br></span></div><div><span style="font-family:monospace">
</span><div><font face="monospace"><font face="arial,sans-serif"><span style="font-family:monospace">+-----------------------------+------+
</span></font></font></div><div><span style="font-family:monospace">
| Package variant | GC 1 |<br></span></div><div><span style="font-family:monospace">
+-----------------------------+------+<br></span></div><div><span style="font-family:monospace">
| Game (DWARFLinker) | 5.7 |
</span><div><span style="font-family:monospace">
| Game (DWARFLinker, no ODR) | 5.8 |</span></div>
</div><div><span style="font-family:monospace">
| Clang (DWARFLinker) | 22.4 |
</span><div><div><span style="font-family:monospace"></span></div>
</div><div><span style="font-family:monospace">
| Clang (DWARFLinker, no ODR) | 22.5 |</span></div>
</div><div><span style="font-family:monospace">
+-----------------------------+------+</span></div><div><span style="font-family:monospace"><br></span></div><div><span style="font-family:monospace"><span style="font-family:arial,sans-serif">My opinion is that the time costs of the DWARF Linker approach are not really practical except on build servers, in the current state of affairs for larger packages: clang takes 8.8x as long as the fragmented approach and 11.2x as long as the plain approach (without the no ODR option). The size saving is certainly good, with my version of clang 51% of the total output size for the DWARF linker approach versus the plain approach and 55% of the fragmented approach (though it is likely that further size savings might be possible for the latter). The game produced reasonable size savings too: 62% and 74%, but I'd be surprised if these gains would be enough for people to want to use the approach in day-to-day situations, which presumably is the main use-case for smaller DWARF, due to improved debugger load times.<br></span></span></div><div><span style="font-family:arial,sans-serif"><br></span></div><div><span style="font-family:monospace"><span style="font-family:arial,sans-serif">Interesting to note is that the GCC 7.5 build of clang I've used these figures with produced no difference in size results between the two variants, unlike other packages. Consequently, a significant amount of time is saved for no penalty.</span><br></span></div><div><span style="font-family:arial,sans-serif"><br></span></div><div><span style="font-family:monospace"><span style="font-family:arial,sans-serif">I'll be interested to see what the time results of the DWARF linker are once further improvements to it have been made.<br></span></span></div><div><span style="font-family:arial,sans-serif"><br></span></div><div><span style="font-family:arial,sans-serif">Thanks,<br></span></div><div><span style="font-family:arial,sans-serif"><br></span></div><div><span style="font-family:monospace"><span style="font-family:arial,sans-serif">James</span><br></span></div></div></div></div></div></div></div></div><blockquote class="gmail_quote" style="margin:0px 0.8ex;border-left:1px solid rgb(204,204,204);border-right:1px solid rgb(204,204,204);padding-left:1ex;padding-right:1ex"><div dir="ltr"><div><div><div><div><div>
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