[clang][Modules] PCM Sizes Increased Significantly After Delta Encoding Optimization Removed

[qiongsiwu]

Hi @hokein @ChuanqiXu9 !

I work with @Bigcheese and @cyndyishida on Clang Modules. We noticed that the PCM sizes have increased significantly (5%) after #145670. I can see that the 5% increase is expected, but combining this with some other commits that increase PCM sizes, we are experiencing build failures where builders run out of disk space.

Do we have a plan going forward to claw back some of the disk space increase caused by this PR?

[llvmbot]

@llvm/issue-subscribers-clang-modules

Author: Qiongsi Wu (qiongsiwu)

Hi @hokein @ChuanqiXu9 !

I work with @Bigcheese and @cyndyishida on Clang Modules. We noticed that the PCM sizes have increased significantly (5%) after #145670. I can see that the 5% increase is expected, but combining this with some other commits that increase PCM sizes, we are experiencing build failures where builders run out of disk space.

Do we have a plan going forward to claw back some of the disk space increase caused by this PR?

[shafik]

CC @rnk @AaronBallman @erichkeane

[shafik]

Can you identify what are the other commits that increase PCM size?

[shafik]

I am going to point out that we do try to take feedback on PRs pretty seriously, especially from key stakeholders but I will additionally say modules PRs usually don't get a lot of feedback outside a small set of people. I would love to see a wider set of folks regularly reviewing modules PRs and maybe this will allow us to address these types issues more effectively earlier in the process.

[qiongsiwu]

Thanks for chiming in @shafik !

Can you identify what are the other commits that increase PCM size?

d3daa3c causes 3% size increase for some of our projects. In total, these two commits are causing an 8% increase, which becomes significant when added together.

[AaronBallman]

I'm not aware of active plans to claw that memory back, but it would certainly be welcome effort to improve compile time overhead, build artifact size, etc.

[qiongsiwu]

Thanks @AaronBallman !

@hokein other than code clean up, what was the intention of #145670? Was it preparing for enabling 64 bit source location?