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Re: [Qemu-devel] [PATCH 0/3] per-TLB lock
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 0/3] per-TLB lock |
Date: |
Wed, 3 Oct 2018 09:56:31 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 |
On 02/10/2018 23:29, Emilio G. Cota wrote:
> This series introduces a per-TLB lock. This removes existing UB
> (e.g. memset racing with cmpxchg on another thread while flushing),
> and in my opinion makes the TLB code simpler to understand.
>
> I had a bit of trouble finding the best place to initialize the
> mutex, since it has to be called before tlb_flush, and tlb_flush
> is called quite early during cpu initialization. I settled on
> cpu_exec_realizefn, since then cpu->env_ptr has been set
> but tlb_flush hasn't yet been called.
>
> Perf-wise this change does have a small impact (~2% slowdown for
> the aarch64 bootup+shutdown test; 1.2% comes from using atomic_read
> consistently), but I think this is a fair price for avoiding UB.
The UB is unlikely to be an issue in practice, but I like the
simplicity. In retrospect it was premature optimization.
Paolo
- [Qemu-devel] [PATCH 3/3] cputlb: read CPUTLBEntry.addr_write atomically, (continued)
- [Qemu-devel] [PATCH 3/3] cputlb: read CPUTLBEntry.addr_write atomically, Emilio G. Cota, 2018/10/02
- [Qemu-devel] [PATCH 1/3] exec: introduce tlb_init, Emilio G. Cota, 2018/10/02
- [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Emilio G. Cota, 2018/10/02
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Alex Bennée, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Paolo Bonzini, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Emilio G. Cota, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Paolo Bonzini, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Emilio G. Cota, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Paolo Bonzini, 2018/10/03
- Re: [Qemu-devel] [PATCH 2/3] cputlb: serialize tlb updates with env->tlb_lock, Emilio G. Cota, 2018/10/03
Re: [Qemu-devel] [PATCH 0/3] per-TLB lock,
Paolo Bonzini <=