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Re: [Qemu-devel] [PATCH 17/22] tcg: distribute profiling counters across
From: |
Emilio G. Cota |
Subject: |
Re: [Qemu-devel] [PATCH 17/22] tcg: distribute profiling counters across TCGContext's |
Date: |
Mon, 10 Jul 2017 12:00:08 -0400 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Sun, Jul 09, 2017 at 11:44:10 -1000, Richard Henderson wrote:
> On 07/09/2017 11:14 AM, Emilio G. Cota wrote:
> >On Sun, Jul 09, 2017 at 10:45:55 -1000, Richard Henderson wrote:
> >>On 07/08/2017 09:50 PM, Emilio G. Cota wrote:
> >>>+ /* includes aborted translations because of exceptions */
> >>>+ atomic_set(&prof->tb_count1, prof->tb_count1 + 1);
> >>
> >>Again, atomic_set without atomic_read is pointless.
> >>Either you're trying to give the compiler extra information, or you aren't.
> >
> >See my comment to patch 3.
>
> I still disagree. It's Just Plain Confusing.
To me,
atomic_set(&foo, foo + 1)
and
atomic_set(&foo, atomic_read(&foo) + 1)
read differently.
The former tells me that no other thread can update the value.
The latter makes me presume that other threads *can* update the value,
which makes me wonder whether this is a bug and we should use atomic_inc(),
or perhaps we are OK with missing counts.
Emilio
- Re: [Qemu-devel] [PATCH 21/22] tcg: enable per-thread TCG for softmmu, (continued)
Re: [Qemu-devel] [PATCH 21/22] tcg: enable per-thread TCG for softmmu, Paolo Bonzini, 2017/07/10
[Qemu-devel] [PATCH 17/22] tcg: distribute profiling counters across TCGContext's, Emilio G. Cota, 2017/07/09
Re: [Qemu-devel] [PATCH 00/22] tcg: per-thread TCG, Emilio G. Cota, 2017/07/09
Re: [Qemu-devel] [PATCH 00/22] tcg: per-thread TCG, Alex Bennée, 2017/07/10