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Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches
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From: |
Alex Bennée |
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Subject: |
Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches |
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Date: |
Wed, 06 Sep 2017 09:55:15 +0100 |
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User-agent: |
mu4e 0.9.19; emacs 25.2.50.3 |
Richard Henderson <address@hidden> writes:
> On 09/05/2017 05:33 PM, Pranith Kumar wrote:
>>> This significantly degrades performance of alpha-softmmu.
>>> It spends about 25% of all cpu time in memset.
>>
>> What workload does it degrade for? I will try to reproduce and see
>> which memset is causing this.
>
> emerge --update --ask @world
>
> which is a lot of python, iirc.
>
> It is the tlb flush memset that is causing this.
> The tlb has grown from a few kB to 300kB with your patch.
Hmm I wonder if this is QEMU doing global flushes which could actually
be partial TLB flushes? emerge is quite a memory hog though so its
conceivable we are generating a lot of churn as it runs.
--
Alex Bennée