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From: tedheadster <tedheadster-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>,
	mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	Matthew Whitehead <whiteheadm-HInyCGIudOg@public.gmane.org>,
	konrad.wilk-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH] x86: enable swiotlb for > 4GiG ram on 32-bit kernels
Date: Thu, 18 Oct 2018 21:00:07 -0400	[thread overview]
Message-ID: <CAP8WD_Z2XvLsqimSnODwr5gj6GRuzh4SMKN56n6Y0JzufG=E8A@mail.gmail.com> (raw)
In-Reply-To: <20181018125116.GA24676-jcswGhMUV9g@public.gmane.org>

> But you said without the fix it doesn't work at all?  Or is this
> the same box, just with the aic7xxx controller disabled?
>
> In general the patch should only have two effects:
>
>  - set a small amount of memory aside for bounce buffering
>  - switch the default dma_ops from dma_direct_ops to swiotlb_ops
>
> I can't really see how either could have such a huge effect, even with
> swiotlb having a couple more wired up ops for which we'd enable spectre
> mitigations.
>
> So a strict before and after would be very interesting, if it is really
> just this one change that causes such a huge drop we have hidden dragons
> somewhere..

Christoph,
  I did a very controlled before-and-after and got very sensible
results. All compiles were close in time with patched and un-patched
kernels.

I must have screwed something up with my last round of testing.

Ingo: I am confident this patch should be accepted.

- Matthew Whitehead

  parent reply	other threads:[~2018-10-19  1:00 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-14  7:52 [PATCH] x86: enable swiotlb for > 4GiG ram on 32-bit kernels Christoph Hellwig
2018-10-14  7:52 ` Christoph Hellwig
2018-10-14  8:13 ` Thomas Gleixner
2018-10-14  8:13   ` Thomas Gleixner
2018-10-14  8:14   ` Christoph Hellwig
2018-10-14  8:14     ` Christoph Hellwig
2018-10-14  8:57     ` Thomas Gleixner
2018-10-14  8:57       ` Thomas Gleixner
2018-10-14  9:04       ` Ingo Molnar
2018-10-14  9:04         ` Ingo Molnar
2018-10-14 12:49         ` tedheadster
2018-10-14  9:18 ` [tip:x86/urgent] x86/swiotlb: Enable " tip-bot for Christoph Hellwig
2018-10-15  9:09 ` tip-bot for Christoph Hellwig
2018-10-15 18:52 ` [PATCH] x86: enable " Konrad Rzeszutek Wilk
2018-10-15 18:52   ` Konrad Rzeszutek Wilk
     [not found] ` <20181014075208.2715-1-hch-jcswGhMUV9g@public.gmane.org>
2018-10-16 13:11   ` tedheadster
     [not found]     ` <CAP8WD_Zj5aMcTCVtV-hot3zLNfNuMzHyeogm0Lqb=+XZ1LdkKw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-17 10:16       ` Thomas Gleixner
2018-10-17 16:33       ` Christoph Hellwig
     [not found]         ` <20181017163351.GA23719-jcswGhMUV9g@public.gmane.org>
2018-10-17 17:41           ` tedheadster
     [not found]             ` <CAP8WD_boL-DxEXxa-ci382Ff8yTdMS9T+sy2Y0-LEX-WPc8L_g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-18 12:51               ` Christoph Hellwig
     [not found]                 ` <20181018125116.GA24676-jcswGhMUV9g@public.gmane.org>
2018-10-19  1:00                   ` tedheadster [this message]
     [not found]                     ` <CAP8WD_Z2XvLsqimSnODwr5gj6GRuzh4SMKN56n6Y0JzufG=E8A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-19  5:51                       ` Ingo Molnar
2018-10-18  6:12       ` Ingo Molnar
2018-10-19  5:54 ` [tip:x86/urgent] x86/swiotlb: Enable swiotlb for > 4GiG RAM " tip-bot for Christoph Hellwig

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