Messages in this thread | | | From | Vlastimil Babka <> | Subject | Re: [PATCH] mm: memory_hotplug: put migration failure information under DEBUG_VM | Date | Tue, 24 Nov 2020 14:39:42 +0100 |
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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.
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