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Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches |
Date: |
Tue, 5 Sep 2017 14:50:35 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 |
On 08/29/2017 10:23 AM, Pranith Kumar wrote:
> This patch increases the number of entries cached in the TLB. I went
> over a few architectures to see if increasing it is problematic. Only
> armv6 seems to have a limitation that only 8 bits can be used for
> indexing these entries. For other architectures, the number of TLB
> entries is increased to a 4K-sized cache. The patch also doubles the
> number of victim TLB entries.
>
> Some statistics collected from a build benchmark for various cache
> sizes is listed below:
>
> | TLB bits\vTLB entires | 8 | 16 | 32 |
> | 8 | 952.94(+0.0%) | 929.99(+2.4%) | 919.02(+3.6%) |
> | 10 | 898.92(+5.6%) | 886.13(+7.0%) | 887.03(+6.9%) |
> | 12 | 878.56(+7.8%) | 873.53(+8.3%)* | 875.34(+8.1%) |
>
> The best combination for this workload came out to be 12 bits for the
> TLB and a 16 entry vTLB cache.
This significantly degrades performance of alpha-softmmu.
It spends about 25% of all cpu time in memset.
r~
- Re: [Qemu-devel] [PATCH] tcg/softmmu: Increase size of TLB caches,
Richard Henderson <=