Re: [PATCH] bsd-user/main: Allow setting tb-size

[Ilya Leoshkevich <iii@linux.ibm.com>]

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On Wed, 2024-07-31 at 15:21 -0600, Warner Losh wrote:
> On Wed, Jul 31, 2024 at 8: 45 AM Ilya Leoshkevich
> <iii@ linux. ibm. com> wrote: While qemu-system can set tb-size using
> -accel tcg,tb-size=n, there is no similar knob for qemu-bsd-user. Add
> one in a way similar to how one-insn-per-tb is already
> 
> 
> 
> On Wed, Jul 31, 2024 at 8:45 AM Ilya Leoshkevich <iii@linux.ibm.com>
> wrote:
> > While qemu-system can set tb-size using -accel tcg,tb-size=n, there
> > is no similar knob for qemu-bsd-user. Add one in a way similar to
> > how
> > one-insn-per-tb is already handled.
> > 
> 
> 
> Cool! Are you using bsd-user and need this for some reason? Or is
> this
> purely theoretical? Is there a larger context I can read about
> somewhere?

I needed this on Linux in order to debug an issue where I suspected
full TB invalidation may be an issue.
It turned out to be something completely different, but I found it
useful: setting it to, e.g., 4096 makes full TB invalidation very rare,
so if a problem is still reproducible, then the root causes is
something else.
Philippe suggested to implement this for BSD as well in order to keep
the interfaces in sync.

[...]


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