From: Martin Pieuchot <mpi@grenadille.net>
Subject: Re: Please test: parallel fault handling
To: tech@openbsd.org, naddy@openbsd.org, robert@openbsd.org, sthen@openbsd.org
Date: Tue, 13 May 2025 14:28:08 +0200

On 13/05/25(Tue) 13:57, Jeremie Courreges-Anglas wrote:
> On Wed, Apr 30, 2025 at 11:39:15AM +0200, Martin Pieuchot wrote:
> > Hello,
> > 
> > Diff below enables running the fault handler in parallel.  Please test
> > an report back, with dmesg, if this increases or decreases the perfs of
> > your usual setup.
> 
> I see a performance improvement in basic testing on an amd64 AMD 8
> cores VM, a Mac Mini M2 pro with 10 cores, a sparc64 LDOM with 16
> cores and a riscv64 Hifive Unmatched with 4 cores.  On the amd64 and
> arm64 machines I have completed a ports bulk build.  Bulk build started
> but unfinished so far on the riscv64 and sparc64 machines - don't hold
> your breath.

Thanks.

> The sparc64 LDOM went into two panics - I somehow managed to break it
> out of ddb after the first panic due to bogus conserver.  The data
> below is minimal, sorry, I didn't recover the full trace from dmesg
> after the 1st panic, and 'mach ddbcpu 0' locked up during the 2nd
> panic.

I wonder if sparc64's pmap is in need for some love...

> 
> I had not run a sparc64 bulk build on this machine in the recent
> months, and I don't know whether both panics are related to your diff,
> but I'll do my best to try and reproduce them.  Currently I've
> restarted the bulk build without the uvm change. Maybe someone with
> more sparc64 knowledge will bring some clue here.

Please let me know.  You can also start by "ps /o" or "show proc".

Thanks!

> First panic:
>   pmap_page_protect: gotten pseg empty!
>   Stopped at      pmap_page_protect+0x594:        nop
> 
> Second panic:
>   ddb{11}> sh panic
>   *cpu11: trap type 0x34 (mem address not aligned): pc=1012f68 npc=1012f6c pstate=820006<PRIV,IE>
>   ddb{11}> tr
>   trap(400fe6b55f0, 34, 1012f68, 820006, 18ec11, 1cd1d60) at trap+0x334
>   Lslowtrap_reenter(4010253a040, 995f566000, deafbeaddeafc10d, 260, 3, 30) at Lslowtrap_reenter+0xf8
>   pmap_page_protect(4001016fa38, 0, 400fe6b5808, 4000d89f2d0, f85dd, 0) at pmap_page_protect+0x2dc
>   uvm_pagedeactivate(4001016f9d0, 19ce130, 17c6578, 40015a505a4, 1, 1) at uvm_pagedeactivate+0x54
>   uvn_flush(40103f05400, 0, 1118e000, 14, 1, 0) at uvn_flush+0x448
>   uvn_detach(40103f05400, 4010c97b080, 4, 0, 0, 1000000) at uvn_detach+0x158
>   uvm_unmap_detach(400fe6b5c68, 0, 9be, 0, 40015a505a4, 17d3558) at uvm_unmap_detach+0x68
>   uvm_map_teardown(4010472d730, 4000, 1889628, 40107720000, 587, 17d4280) at uvm_map_teardown+0x184
>   uvmspace_free(1c7d000, 4010472d730, 4, 17d4280, 0, 6) at uvmspace_free+0x64
>   reaper(40015a505a0, 40015a505a0, ce, 100, f02662b0, 4000) at reaper+0xf8
>   proc_trampoline(0, 0, 0, 0, 0, 0) at proc_trampoline+0x10
> 
> My 2 cents,
> -- 
> jca
>