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Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy

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On Thu 01-12-16 17:03:52, Michal Nazarewicz wrote:
> On Thu, Dec 01 2016, Michal Hocko wrote:
> > Let's also CC Marek
> >
> > On Thu 01-12-16 08:43:40, Vlastimil Babka wrote:
> >> On 12/01/2016 08:21 AM, Michal Hocko wrote:
> >> > Forgot to CC Joonsoo. The email thread starts more or less here
> >> > http://lkml.kernel.org/r/20161130092239.GD18437@dhcp22.suse.cz
> >> > 
> >> > On Thu 01-12-16 08:15:07, Michal Hocko wrote:
> >> > > On Wed 30-11-16 20:19:03, Robin H. Johnson wrote:
> >> > > [...]
> >> > > > alloc_contig_range: [83f2a3, 83f2a4) PFNs busy
> >> > > 
> >> > > Huh, do I get it right that the request was for a _single_ page? Why do
> >> > > we need CMA for that?
> >> 
> >> Ugh, good point. I assumed that was just the PFNs that it failed to migrate
> >> away, but it seems that's indeed the whole requested range. Yeah sounds some
> >> part of the dma-cma chain could be smarter and attempt CMA only for e.g.
> >> costly orders.
> >
> > Is there any reason why the DMA api doesn't try the page allocator first
> > before falling back to the CMA? I simply have a hard time to see why the
> > CMA should be used (and fragment) for small requests size.
> 
> There actually may be reasons to always go with CMA even if small
> regions are requested.  CMA areas may be defined to map to particular
> physical addresses and given device may require allocations from those
> addresses.  This may be more than just a matter of DMA address space.
> I cannot give you specific examples though and I might be talking
> nonsense.

I am not familiar with this code so I cannot really argue but a quick
look at rmem_cma_setup doesn't suggest any speicific placing or
anything...

-- 
Michal Hocko
SUSE Labs

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PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs busy "Robin H. Johnson" <robbat2@orbis-terrarum.net> - 2016-11-29 23:50 +0100
  Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs  busy Michal Hocko <mhocko@kernel.org> - 2016-11-30 10:30 +0100
    Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs busy Michal Nazarewicz <mina86@mina86.com> - 2016-11-30 14:10 +0100
      Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs  busy Michal Hocko <mhocko@kernel.org> - 2016-11-30 14:30 +0100
        Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs  busy "Robin H. Johnson" <robbat2@gentoo.org> - 2016-11-30 21:00 +0100
          drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy "Robin H. Johnson" <robbat2@gentoo.org> - 2016-11-30 21:20 +0100
            Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Vlastimil Babka <vbabka@suse.cz> - 2016-11-30 22:30 +0100
              Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy "Robin H. Johnson" <robbat2@gentoo.org> - 2016-12-01 07:30 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Vlastimil Babka <vbabka@suse.cz> - 2016-12-01 08:40 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy "Robin H. Johnson" <robbat2@gentoo.org> - 2016-12-01 09:00 +0100
            Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Hocko <mhocko@kernel.org> - 2016-12-01 08:20 +0100
              Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Hocko <mhocko@kernel.org> - 2016-12-01 08:30 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Vlastimil Babka <vbabka@suse.cz> - 2016-12-01 08:50 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Hocko <mhocko@kernel.org> - 2016-12-01 15:20 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Nazarewicz <mina86@mina86.com> - 2016-12-01 17:10 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Hocko <mhocko@kernel.org> - 2016-12-01 17:20 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Michal Nazarewicz <mina86@mina86.com> - 2016-12-01 22:10 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Vlastimil Babka <vbabka@suse.cz> - 2016-12-02 07:40 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy  busy Lucas Stach <l.stach@pengutronix.de> - 2016-12-02 11:30 +0100
                Re: drm/radeon spamming alloc_contig_range: [xxx, yyy) PFNs busy busy Jerome Glisse <j.glisse@gmail.com> - 2016-12-02 16:20 +0100
          Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs busy Michal Nazarewicz <mina86@mina86.com> - 2016-12-01 02:40 +0100

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