Re: PROBLEM-PERSISTS: dmesg spam: alloc_contig_range: [XX, YY) PFNs busy
From: Michal Nazarewicz <hidden>
Date: 2016-12-01 01:39:42
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On Wed, Nov 30 2016, Robin H. Johnson wrote:
(I'm going to respond directly to this email with the stack trace.) On Wed, Nov 30, 2016 at 02:28:49PM +0100, Michal Hocko wrote:quoted
quoted
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.Here's what I whipped up based on that, to ensure that dump_stack got rate-limited at the same pass as PFNs-busy. It dropped the dmesg spew to ~25MB/hour (and is suppressing ~43 entries/second right now). commit 6ad4037e18ec2199f8755274d8a745a9904241a1 Author: Robin H. Johnson [off-list ref] Date: Wed Nov 30 10:32:57 2016 -0800 mm: ratelimit & trace PFNs busy. Signed-off-by: Robin H. Johnson [off-list ref]
Acked-by: Michal Nazarewicz <redacted>
quoted hunk ↗ jump to hunk
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6de9440e3ae2..3c28ec3d18f8 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -7289,8 +7289,15 @@ 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", - __func__, outer_start, end); + static DEFINE_RATELIMIT_STATE(ratelimit_pfn_busy, + DEFAULT_RATELIMIT_INTERVAL, + DEFAULT_RATELIMIT_BURST); + if (__ratelimit(&ratelimit_pfn_busy)) { + pr_info("%s: [%lx, %lx) PFNs busy\n", + __func__, outer_start, end);
I’m thinking out loud here, but maybe it would be useful to include a count of how many times this message has been suppressed?
+ dump_stack();
Perhaps do it only if CMA_DEBUG? + if (IS_ENABLED(CONFIG_CMA_DEBUG)) + dump_stack();
+ } + ret = -EBUSY; goto done; } -- Robin Hugh Johnson Gentoo Linux: Dev, Infra Lead, Foundation Trustee & Treasurer E-Mail : robbat2@gentoo.org GnuPG FP : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85 GnuPG FP : 7D0B3CEB E9B85B1F 825BCECF EE05E6F6 A48F6136
-- Best regards ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ «If at first you don’t succeed, give up skydiving»