From: Vlastimil Babka <vbabka@suse.cz>
To: Charan Teja Kalla <charante@codeaurora.org>,
Michal Hocko <mhocko@suse.com>
Cc: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
"vinmenon@codeaurora.org" <vinmenon@codeaurora.org>
Subject: Re: [PATCH] mm: memory_hotplug: put migration failure information under DEBUG_VM
Date: Tue, 24 Nov 2020 14:39:42 +0100 [thread overview]
Message-ID: <775a56a9-b301-31bb-cd6d-8b82b1dd4d65@suse.cz> (raw)
In-Reply-To: <bfa430f6-a6a6-8b08-2776-cb62197619c0@codeaurora.org>
On 11/23/20 4:10 PM, Charan Teja Kalla wrote:
>
> Thanks Michal!
> On 11/23/2020 7:43 PM, Michal Hocko wrote:
>> On Mon 23-11-20 19:33:16, Charan Teja Reddy wrote:
>>> When the pages are failed to get isolate or migrate, the page owner
>>> information along with page info is dumped. If there are continuous
>>> failures in migration(say page is pinned) or isolation, the log buffer
>>> is simply getting flooded with the page owner information. As most of
>>> the times page info is sufficient to know the causes for failures of
>>> migration or isolation, place the page owner information under DEBUG_VM.
>>
>> I do not see why this path is any different from others that call
>> dump_page. Page owner can add a very valuable information to debug
>> the underlying reasons for failures here. It is an opt-in debugging
>> feature which needs to be enabled explicitly. So I would argue users
>> are ready to accept a lot of data in the kernel log.
>
> Just thinking how frequently failures can happen in those paths. In the
> memory hotplug path, we can flood the page owner logs just by making one
> page pinned. Say If it is anonymous page, the page owner information
So you say it's flooded when page_owner info is included, but not
flooded when only the rest of __dump_page() is printed? (which is also
not just one or two lines). That has to be very specific rate of failures.
Anyway I don't like the solution with arbitrary config option. To
prevent flooding we generally have ratelimiting, how about that?
Also agreed with Michal that page_owner is explicitly enabled debugging
option and if you use it in production, that's rather surprising to me,
and possibly more rare than DEBUG_VM, which IIRC Fedora kernels use.
next prev parent reply other threads:[~2020-11-24 13:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-23 14:03 [PATCH] mm: memory_hotplug: put migration failure information under DEBUG_VM Charan Teja Reddy
2020-11-23 14:08 ` David Hildenbrand
2020-11-23 14:13 ` Michal Hocko
2020-11-23 15:10 ` Charan Teja Kalla
2020-11-24 7:41 ` Michal Hocko
2020-11-25 10:48 ` Charan Teja Kalla
2020-11-26 9:18 ` Michal Hocko
2020-11-27 10:23 ` Charan Teja Kalla
2020-11-27 12:02 ` Michal Hocko
2020-11-24 13:39 ` Vlastimil Babka [this message]
2020-11-25 11:10 ` Charan Teja Kalla
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