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Re: [Qemu-devel] [RFC v3] translate-all: protect code_gen_buffer with RC
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [RFC v3] translate-all: protect code_gen_buffer with RCU |
Date: |
Mon, 09 May 2016 16:05:44 +0100 |
User-agent: |
mu4e 0.9.17; emacs 25.0.93.5 |
Paolo Bonzini <address@hidden> writes:
> On 09/05/2016 13:50, Alex Bennée wrote:
>> > Which locks? tb_lock during tb_find_fast? The problem with that was
>> > that it slowed down everything a lot, wasn't it?
>>
>> Very much so, in the new tree (coming soon) with QHT I was able to
>> remove the locks from the whole hot-path which means they where only
>> needed for code generation.
>
> Okay, I'm curious now. :)
https://github.com/stsquad/qemu/commits/mttcg/base-patches-v3 is the
current WIP, with:
https://github.com/stsquad/qemu/commit/0823f1c77f12ed5958f77484d6477ea205aee220
being the commit that clears the hot-path to run without locks.
The tree is based on tcg-next which has made things a lot cleaner now a
bunch of Sergey's stuff has been grabbed by rth. Obviously being WIP
subject to change. Once I'm done with my current out-of-tree diversions
I'll be back onto cleaning the tree up for the next review round.
Review comments on the posted tree's always welcome of course ;-)
>
>> > To me, the RCU idea is not really about making tb_flush (the rare case)
>> > faster; it was more about keeping the rest simple and fast.
>>
>> I'm not sure it achieved that as there is added complexity from having
>> the split buffer and then ensuring you don't double-flush.
>
> Agreed.
>
> Paolo
--
Alex Bennée