From: Otto Moerbeek <otto@drijf.net>
Subject: Re: timing lld --threads for fun and profit
To: Stuart Henderson <stu@spacehopper.org>
Cc: Landry Breuil <landry@openbsd.org>, robert@openbsd.org, tech@openbsd.org
Date: Sat, 9 Nov 2024 09:19:37 +0100

On Sat, Nov 09, 2024 at 09:14:46AM +0100, Otto Moerbeek wrote:

> On Fri, Nov 08, 2024 at 01:01:50PM +0000, Stuart Henderson wrote:
> 
> > On 2024/11/08 13:26, Martin Pieuchot wrote:
> > > On 08/11/24(Fri) 12:22, Landry Breuil wrote:
> > > > [...] 
> > > > someone(tm) should look into patching lld to avoid using more than
> > > > MAX(ncpu,5) threads ? In the meantime, i'll probably fix the firefox
> > > > ports to avoir using MAKE_JOBS for lld but cap it at 5.
> > > 
> > > Recent lld(1) include the following commits which limit the value to
> > > 16 by default instead of the number of available CPUs.
> > > 
> > > See the following commits:
> > > 
> > > https://github.com/llvm/llvm-project/commit/a8788de1c3f3c8c3a591bd3aae2acee1b43b229a
> > > https://github.com/llvm/llvm-project/commit/da68d2164efcc1f5e57f090e2ae2219056b120a0
> > > 
> > > Robert do you see the same with chromium?  Would it make sense to
> > > backport these diff with a smaller value for OpenBSD?
> > > 
> > 
> > Certainly helps for reorder_kernel.
> 
> It might be interesting to play with the number of malloc thread pools

or rather memory pools

> as well.  There are undocumented malloc options to double/half the
> number: + and -. Default is 8, maximum is 32. 
> 
> Which reminds me of the idea to try to make the default dependent on
> the number of online CPUs. Never got around to trying that and see if
> if it matters.
> 
> 	-Otto
> 
> > 
> > $ sysctl hw.{model,ncpu,version}
> > hw.model=12th Gen Intel(R) Core(TM) i5-1245U
> > hw.ncpu=12
> > hw.version=ThinkPad T14 Gen 3
> > 
> > # \time -l /usr/libexec/reorder_kernel
> >         7.30 real         6.86 user         3.92 sys
> >     879280  maximum resident set size
> >          0  average shared memory size
> >          0  average unshared data size
> >          0  average unshared stack size
> >     147812  minor page faults
> >      79421  major page faults
> >          0  swaps
> >      11833  block input operations
> >      15643  block output operations
> >          1  messages sent
> >          0  messages received
> >         45  signals received
> >      46512  voluntary context switches
> >       7353  involuntary context switches
> > # vi Makefile
> > [...]
> > $ grep ^LINKFL Makefile
> > LINKFLAGS=	-T ld.script -X --warn-common -nopie -Wl,--threads=5
> > LINKFLAGS+=	-S
> > # \time -l /usr/libexec/reorder_kernel
> >         0.41 real         0.26 user         0.09 sys
> >     100920  maximum resident set size
> >          0  average shared memory size
> >          0  average unshared data size
> >          0  average unshared stack size
> >      17119  minor page faults
> >         10  major page faults
> >          0  swaps
> >          5  block input operations
> >         78  block output operations
> >          1  messages sent
> >          0  messages received
> >         28  signals received
> >        189  voluntary context switches
> >          2  involuntary context switches
> > 
>