Re: PHP performance on Xen domU with mulitple vcpu

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

> Date: Sun, 6 Apr 2025 23:50:37 +0000
> From: Emmanuel Dreyfus <manu%netbsd.org@localhost>
> 
> On Sun, Apr 06, 2025 at 03:50:44AM +0000, Taylor R Campbell wrote:
> > Try the attached patch?
> 
> I restarted with stock 10.0 XEN3_DOMU kernel to get dtrace working
> (it does not), but now the problem seems to have vanished. I run
> with two vcpu and timecounter xen_system_time, ntpd syncs without
> a hithch. This is a bit frustrating. Perhaps it needs more load
> to fail.
> 
> Loading dtrace module fails on this:
> kobj_checksyms, 1004: [solaris]: linker error: symbol `sdt_provider_sdt' not found
> WARNING: module error: unable to affix module `solaris', error 8
> WARNING: module error: recursive load failed for `dtrace' (`solaris' required), error 8
> 
> I cannot find sdt_provider_sdt anywhere in kernel sources. 

Defined in kern_sdt.c by

SDT_PROVIDER_DEFINE(sdt);

Requires `options KDTRACE_HOOKS' in the kernel you want to load dtrace
into.  This was only added to amd64/XEN3_DOMU in the netbsd-10 branch
a week ago.

However, I seem to recall there is a problem where the Xen loader
doesn't pass the CTF data to NetBSD, so it's considerably less useful
than it should be -- this might be why I held off on requesting pullup
myself.  The dtrace script I suggested should work but if you try to
use anything that requires dtrace to know about types, like printing
args[N] rather than argN or reading named structure members, it might
not work.