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From: | Paolo Bonzini |
Subject: | [Qemu-devel] Re: [PATCH] qemu/pci: optimize pci config handling |
Date: | Thu, 08 Oct 2009 10:23:41 +0200 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-2.7.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4 |
What you porpose here is certainly more code than we had. So why is this a good idea?Because it avoids the memcpy/memcmp most of the time (when the memcmp would surely succeed).Yes :) But at the cost of more code. I don't think speed matters there, so less code is good.
Fine.
I supposed that would also matter more as the config space size increases---correct me and dismiss the patch if I am mistaken.No, we'll always only look need to look at the header, whatever the size of the config space. That's the point of the patch I posted - future proof against config space size increases, not optimization.
But fewer reads on average will not modify the header, so there will be even fewer memcpy with my patch when the config space will be 4k.
Paolo
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