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Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs busy

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On Wed 30-11-16 14:08:00, Michal Nazarewicz wrote:
> On Wed, Nov 30 2016, Michal Hocko wrote:
> > [Let's CC linux-mm and Michal]
> >
> > On Tue 29-11-16 22:43:08, Robin H. Johnson wrote:
> >> I didn't get any responses to this.
> >> 
> >> git bisect shows that the problem did actually exist in 4.5.0-rc6, but
> >> has gotten worse by many orders of magnitude (< 1/week to ~20M/hour).
> >> 
> >> Presently with 4.9-rc5, it's now writing ~2.5GB/hour to syslog.
> >
> > This is really not helpful. I think we should simply make it pr_debug or
> > need some ratelimitting.  AFAIU the message is far from serious
> 
> On the other hand, if this didn’t happen and now happens all the time,
> this indicates a regression in CMA’s capability to allocate pages so
> just rate limiting the output would hide the potential actual issue.

Or there might be just a much larger demand on those large blocks, no?
But seriously, dumping those message again and again into the low (see
the 2.5_GB_/h to the log is just insane. So there really should be some
throttling.

Does the following help you Robin. At least to not get swamped by those
message.
---
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0fbfead6aa7d..96eb8d107582 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7424,7 +7424,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 
 	/* Make sure the range is really isolated. */
 	if (test_pages_isolated(outer_start, end, false)) {
-		pr_info("%s: [%lx, %lx) PFNs busy\n",
+		printk_ratelimited(KERN_DEBUG "%s: [%lx, %lx) PFNs busy\n",
 			__func__, outer_start, end);
 		ret = -EBUSY;
 		goto done;

I would also suggest to add dump_stack() to that path to see who is
actually demanding so much large continuous blocks.
-- 
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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