[PATCH] D26130: [ELF] - Implemented --symbol-ordering-file option.

[George Rimar via llvm-commits]

grimar added a comment.

In https://reviews.llvm.org/D26130#583948, @ruiu wrote:

> Well, again, you really need to run a long sequence of computations to get meaningful numbers for benchmark. `clang -help` isn't useful for that purpose.


Yes, Rui, please don't think I forgot about that opinion :) clang -help looks good because of very stable results. As I pointed I observe the same amount of faults for the same binary on 2 different PC. So it defenetely (IMO) proves that patch can be used to reduce them during startup.

In https://reviews.llvm.org/D26130#583961, @davide wrote:

> In https://reviews.llvm.org/D26130#583948, @ruiu wrote:
>
> > Well, again, you really need to run a long sequence of computations to get meaningful numbers for benchmark. `clang -help` isn't useful for that purpose.
>
>
> Agree (as already pointed out in the other thread review). I discussed this a bit with Rafael and I see his point of view, i.e. `clang -help` is definitely a sanity check, and the number of page faults being decreased is a good thing, but I'd really love this to be tested on a startup-time sensitive application.
>  I mentioned browsers, in particular Firefox, because the Mozilla people spent quite a bit of time thinking about the problem, so you should be able to reuse all their infrastructure (tests etc..). Firefox should link out-the-box with lld, and if it doesn't .. well there's more work to to there =)


I did not yet try firefox with this patch. But as I wrote in another thread, I was unable to obtain a boost using --sections-ordering-file on clang and firefox previously. Though sections file for firefox produces by icegrind was 5 megabytes in size, what is much more than 300 entries that works with this patch.
So the noticable result using --symbol-ordering-file and Rafael's method of generating it is probably  a step forward that was worth to share.

Will try to test firefox using this patch.

(about linking firefox with lld. When last time I did that, it produced next error for me during launch:

> umb at ubuntu:~/firefox/clean/mozilla-central$ /home/umb/firefox/clean/mozilla-central/obj-x86_64-pc-linux-gnu/dist/bin/firefox -no-remote -profile /home/umb/firefox/clean/mozilla-central/obj-x86_64-pc-linux-gnu/tmp/scratch0
>  XPCOMGlueLoad error for file /home/umb/firefox/clean/mozilla-central/obj-x86_64-pc-linux-gnu/dist/bin/libxul.so:
>  /home/umb/firefox/clean/mozilla-central/obj-x86_64-pc-linux-gnu/dist/bin/libxul.so: undefined symbol: gtk_main_do_event
>  Couldn't load XPCOM.

so I had to link firefox with gold and then relink libxul.so with lld. That should have being fine I think since that is the single core library of firefox and sections file was targeted for it.
And anyways latest tests I performed on vanilla gold to check the option itself, and result was the same).


https://reviews.llvm.org/D26130