Re: Any progress on horrible IPoIB perf with kernel 4.5+?

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On 7/6/2016 1:09 PM, Roland Dreier wrote:
> Hi,
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=111921 describes a
> performance regression introduced by commit 9207f9d45b0a ("net:
> preserve IP control block during GSO segmentation").  I've recently
> run into this when updating my system, since that commit hit stable
> kernel 4.4.y — in my case I noticed because scp over an IPoIB link
> went from ~200 MB/sec down to below 1 MB/sec.  I confirmed that
> reverting that change did fix my performance.
> 
> Obviously just reverting that commit isn't the right answer, since I
> believe the patch description that says the commit fixes a crash.
> However before I start working on this myself, I want to make sure I'm
> not duplicating anyone else's work.  Doug, you mentioned having time
> to work on it back in May — did you figure anything out?  Or is anyone
> else investigating this?
> 
> Thanks,
>   Roland
> 

I *just* came back from PTO.  I'm still working through my email (where
I saw your writeup of this issue).  I didn't get very far with the issue
back in May, but that's because I didn't have a lot of the background
information you supplied in the other thread and didn't have the time to
dig it out on my own.  I could probably make some progress now.

-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
    GPG Key ID: 0E572FDD


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