Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754163AbcL3WPW (ORCPT ); Fri, 30 Dec 2016 17:15:22 -0500 Received: from anholt.net ([50.246.234.109]:54724 "EHLO anholt.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753861AbcL3WPU (ORCPT ); Fri, 30 Dec 2016 17:15:20 -0500 From: Eric Anholt To: Michal Nazarewicz , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-stable , "Robin H. Johnson" , Vlastimil Babka , Marek Szyprowski Subject: Re: [PATCH] mm: Drop "PFNs busy" printk in an expected path. In-Reply-To: References: <20161229023131.506-1-eric@anholt.net> <20161229091256.GF29208@dhcp22.suse.cz> <87wpeitzld.fsf@eliezer.anholt.net> <8737h65nr5.fsf@eliezer.anholt.net> User-Agent: Notmuch/0.22.2+1~gb0bcfaa (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Fri, 30 Dec 2016 12:25:00 -0800 Message-ID: <87bmvtxizn.fsf@eliezer.anholt.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3418 Lines: 84 --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Michal Nazarewicz writes: > On Thu, Dec 29 2016, Eric Anholt wrote: >> Michal Nazarewicz writes: >> >>> On Thu, Dec 29 2016, Eric Anholt wrote: >>>> Michal Hocko writes: >>>> >>>>> This has been already brought up >>>>> http://lkml.kernel.org/r/20161130092239.GD18437@dhcp22.suse.cz and th= ere >>>>> was a proposed patch for that which ratelimited the output >>>>> http://lkml.kernel.org/r/20161130132848.GG18432@dhcp22.suse.cz resp. >>>>> http://lkml.kernel.org/r/robbat2-20161130T195244-998539995Z@orbis-ter= rarum.net >>>>> >>>>> then the email thread just died out because the issue turned out to b= e a >>>>> configuration issue. Michal indicated that the message might be useful >>>>> so dropping it completely seems like a bad idea. I do agree that >>>>> something has to be done about that though. Can we reconsider the >>>>> ratelimit thing? >>>> >>>> I agree that the rate of the message has gone up during 4.9 -- it used >>>> to be a few per second. >>> >>> Sounds like a regression which should be fixed. >>> >>> This is why I don=E2=80=99t think removing the message is a good idea. = If you >>> suddenly see a lot of those messages, something changed for the worse. >>> If you remove this message, you will never know. >>> >>>> However, if this is an expected path during normal operation, >>> >>> This depends on your definition of =E2=80=98expected=E2=80=99 and =E2= =80=98normal=E2=80=99. >>> >>> In general, I would argue that the fact those ever happen is a bug >>> somewhere in the kernel =E2=80=93 if memory is allocated as movable, it= should >>> be movable damn it! >> >> I was taking "expected" from dae803e165a11bc88ca8dbc07a11077caf97bbcb -- >> if this is a actually a bug, how do we go about debugging it? > > That=E2=80=99s why I=E2=80=99ve pointed out that this depends on the defi= nition. In my > opinion it=E2=80=99s a design bug which is now nearly impossible to fix in > efficient way. OK, so the design is bad. When you said bug, I definitely thought you were saying that the message shouldn't happen in the design. Given CMA's current design, should everyone using CMA see their logs slowly growing with this message that is an secret code for "CMA's design hasn't yet changed"? If you want to have people be able to track how often this is happening, let's make a perf event for it or something instead. --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE/JuuFDWp9/ZkuCBXtdYpNtH8nugFAlhmwpwACgkQtdYpNtH8 nujh/xAArfUZW+F7uX/TMkYR+XCNon6ZYMObQe3HsNKYW6g5ij32hR0HSO7OnTNY WKdVMeTx6XvNMx7xGYmCHg/EFGJWSnEPR1A34/on5M1hCeJQQhl/ZZ7gOaQv2NMA igwr6X509/+WAY/wnKaBhDscnbGaBBXwcrS6E2fJdpmDBAOUD6Lf/js3ucqf5FVV uU9TQSH+KQaACLIvsEoMFSjAD+Q4UpDKFTQsYHOTspP3tX/+s2FsB2NU6QUfk511 lVxx1ltN8hI1yYkEFkMQGm4PJfHTo1N5ikdWnorGjd4pQnRn2DGJWOpv1i0WrsGZ 53Wv9ehPrHBWLrWmw8sH8YK/sypDpvANQhJaQr96/OOKjLHHrBZOhhJBWebcnyh9 B4uxD3Gwby54wWK6krLUlddfV2uPn9b3KKQn9gw/PeWi0GByMcYkw+H6ctsw2Nu0 HJpVpTOpMZjFQ7tDxNBrh9qJuQa2XQRgndYgkgoF6RoPCCBbhO0sntzSxLAd8MWa Xv0TUgY+mtC92sdtshocyHWZYbm5rgJFQ+vVqKXU5rIi213tkaD//XwvCVclR7JF egW2WQQ8sLKUmmOzgnyZ9A4lzjrJ8MtCkKx3ydLa+XeC2wDK3231xjjq1PWL28JB g8IRTpcSyo4lZ+E9ewyexA3UHwfZeWn5INP2RDgyElIKJF9PJLM= =+U63 -----END PGP SIGNATURE----- --=-=-=--