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Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line |
Date: |
Tue, 25 Oct 2016 22:58:00 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 25/10/2016 22:45, Emilio G. Cota wrote:
> On Tue, Oct 25, 2016 at 16:35:48 -0400, Pranith Kumar wrote:
>> On Tue, Oct 25, 2016 at 4:02 PM, Paolo Bonzini <address@hidden> wrote:
>>>
>>>
>>>> I've written a patch (see below) to take the per-bucket sequence locks.
>>>
>>> What's the performance like?
>>>
>>
>> Applying only this patch, the perf numbers are similar to the 128
>> cache line alignment you suggested.
>
> That makes sense. Having a single seqlock per bucket is simple and fast;
> note that bucket chains should be very short (we use good hashing and
> automatic resize for this purpose).
But why do we get such worse performance in the 100% reader case? (And
even more puzzling, why does Pranith's original patch improve
performance instead of causing more cache misses?)
Thanks,
Paolo
- [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Pranith Kumar, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Paolo Bonzini, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Pranith Kumar, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Paolo Bonzini, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Pranith Kumar, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Paolo Bonzini, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Pranith Kumar, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Emilio G. Cota, 2016/10/25
- Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line,
Paolo Bonzini <=
Re: [Qemu-devel] [RFC PATCH] qht: Align sequence lock to cache line, Emilio G. Cota, 2016/10/25