lkml.org 
[lkml]   [2021]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 01/13] objtool: Rewrite hashtable sizing
From
Date
On 6/10/2021 11:43 AM, Peter Zijlstra wrote:
> On Thu, Jun 10, 2021 at 11:14:51AM -0700, Nathan Chancellor wrote:
>
>> This patch as commit 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing")
>> in -tip causes a massive compile time regression with allmodconfig +
>> ThinLTO.
>
> Moo... the allyesconfig builds I used it on were much faster, but that
> was on regular GCC vmlinux.o after linking.
>
>> Adding Sami because I am not sure why this patch would have much of an impact
>> in relation to LTO. https://git.kernel.org/tip/25cf0d8aa2a3 is the patch in
>> question.
>>
>> If I can provide any further information or help debug, please let me know.
>>
>> If you are interested in reproducing this locally, you will need a
>> fairly recent LLVM stack (I used the stable release/12.x branch) and to
>> cherry-pick commit 976aac5f8829 ("kcsan: Fix debugfs initcall return
>> type") to fix an unrelated build failure. My script [2] can build a
>> self-contained toolchain fairly quickly if you cannot get one from your
>> package manager. A command like below will speed up the build a bit:
>
> Would something like llvm-13 from Debian be good enough?
>
> $ clang-13 --version
> Debian clang version 13.0.0-++20210418105309+a0898f0cecc7-1~exp1
> Target: x86_64-pc-linux-gnu
> Thread model: posix
> InstalledDir: /usr/bin
>

Yes, that would work. That is what we use in our CI.

Looks like Sami gave a reply that explains it.

Cheers,
Nathan

\
 
 \ /
  Last update: 2021-06-10 20:55    [W:0.555 / U:0.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site