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Re: [Qemu-devel] [RFC 38/38] Revert "target-i386: yield to another VCPU
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC 38/38] Revert "target-i386: yield to another VCPU on PAUSE" |
Date: |
Sun, 23 Aug 2015 18:29:58 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 23/08/2015 17:24, Emilio G. Cota wrote:
> This reverts commit 81f3053b77f7d3a4d9100c425cd8cec99ee7a3d4.
>
> The interrupt raised by the change in the commit above
> kills performance when running many idling VCPUs. For example,
> on my 64-core host when running a workload where cores are
> idling often (e.g. blackscholes), performance drops significantly
> because threads are most of the time just exiting the CPU loop,
> thereby causing great contention on the BQL.
>
> Fix it by reverting to the old behaviour by which no
> interrupt is raised, which shouldn't be an issue given that
> we have now one thread per VCPU.
>
> Signed-off-by: Emilio G. Cota <address@hidden>
Agreed, this is not necessary anymore!
Paolo
- Re: [Qemu-devel] [RFC 22/38] cpu: update interrupt_request atomically, (continued)
- [Qemu-devel] [RFC 31/38] cpu: protect l1_map with tb_lock in full-system mode, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 27/38] cpu-exec: convert tb_invalidated_flag into a per-TB flag, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 33/38] cpu: introduce cpu_tcg_sched_work to run work while other CPUs sleep, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 21/38] target-i386: emulate atomic instructions + barriers using AIE, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 38/38] Revert "target-i386: yield to another VCPU on PAUSE", Emilio G. Cota, 2015/08/23
- Re: [Qemu-devel] [RFC 38/38] Revert "target-i386: yield to another VCPU on PAUSE",
Paolo Bonzini <=
- [Qemu-devel] [RFC 37/38] cpus: remove async_run_safe_work_on_cpu, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 32/38] cpu list: convert to RCU QLIST, Emilio G. Cota, 2015/08/23
- [Qemu-devel] [RFC 28/38] cpu-exec: use RCU to perform lockless TB lookups, Emilio G. Cota, 2015/08/23
- Re: [Qemu-devel] [RFC 00/38] MTTCG: i386, user+system mode, Paolo Bonzini, 2015/08/24
- Re: [Qemu-devel] [RFC 00/38] MTTCG: i386, user+system mode, Artyom Tarasenko, 2015/08/24