Date: Tue, 14 May 2024 10:14:22 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Ryan Libby <rlibby@freebsd.org> Cc: =?UTF-8?Q?Bojan_Novkovi=C4=87?= <bnovkov@freebsd.org>, Current <current@freebsd.org>, alc@freebsd.org Subject: Re: Graph of the FreeBSD memory fragmentation Message-ID: <09dd93a8c9bf836f061413c30d0b14c6@Leidinger.net> In-Reply-To: <CAHgpiFyb7=p2QKdXsMw7e2FiU%2Beqmx3AEaV3HXTJqJzgnkx=Pw@mail.gmail.com> References: <0a3ddc685e54a289ff5cff569a95cd29@Leidinger.net> <5c7357c3-5a10-4a8e-9245-8a5787c57f35@freebsd.org> <ee8365d5773c5b178d443daf92484bf5@Leidinger.net> <CAHgpiFyb7=p2QKdXsMw7e2FiU%2Beqmx3AEaV3HXTJqJzgnkx=Pw@mail.gmail.com>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --=_3317caf2e94c14a573bd9e0b5c0e31e1 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed Am 2024-05-14 03:54, schrieb Ryan Libby: > That was a long winded way of saying: the "UMA bucket" axis is > actually "vm phys free list order". > > That said, I find that dimension confusing because in fact there's > just one piece of information there, the average size of a free list > entry, and it doesn't actually depend on the free list order. The > graph could be 2D. It evolved into that... At first I had a 3 dimensional dataset and the first try was to plot it as is (3D). The outcome (as points) was not as good as I wanted it to be, and plotting as lines gave the wrong direction of lines. I massaged the plotting instructions until it looked good enough. I did not try a 2D plot. I agree, with different colors for each free list order a 2D plot may work too. If a 2D plot is better than a 3D plot in this case, depends on the mental model of the topic the viewer has. One size may not fit all. Feel free to experiment with other plotting styles. > The paper that defines this fragmentation index also says that "the > fragmentation index is only meaningful when an allocation fails". Are > you actually seeing any contiguous allocations failures in your > measurements? I'm not aware of such. The index may only be meaningful for the purposes of the goal of the paper when there are such failures, but if you look at the graph and how it changed when Bojan changed the guard pages, I see value in the graph for more than what the paper suggests. > Without that context, it seems like what the proposed sysctl reports > is indirectly just the average size of free list entries. We could > just report that. The calculation of the value is part of a bigger picture. The value returned is used by some other code to make decisions. Bye, Alexander. -- http://www.Leidinger.net Alexander@Leidinger.net: PGP 0x8F31830F9F2772BF http://www.FreeBSD.org netchild@FreeBSD.org : PGP 0x8F31830F9F2772BF --=_3317caf2e94c14a573bd9e0b5c0e31e1 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc; size=833 Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEER9UlYXp1PSd08nWXEg2wmwP42IYFAmZDHWwACgkQEg2wmwP4 2IaV4hAAlFq7L0RJp07vEB4P96BrUKtO2QXTeJBUDXN2rg7uDlp0ZPWDzNc5E2+C Jh7mcYnEgHq/ByofD2AGwhpsrwrGzQvI9P+4HL4kg+ePvIh97PloBlbwigTf8x/H cLU/XsovXs6VtKi6vmUCShjGacQ9cDZv3AriyqzYA1F/3V0bCh0pVCtok31QzeyP jGZgyofR9B4pvETMNVcv5Dx+JEqqXiuf1HWXl6xrRNf+pQPgp+Bg7ki4VXaMORuY ZW8Vn8mHog7YQLfb+pRWOmwFGe2eXzL2hIGXXyoBYAYmMpjli+/xnFtki0vWqnOl 9oho4Tm/MLLqskEq7FPY3jRwGsKsLKRSkLhSpFWeDG0yOdPb7jie5XLvWq430Rp+ xUvVIAcuF/g5YqL1/kRCTCZmTATKYe90AHvqb0szkGYqIIoq7SVENUX+4j8mlWcL +pDgef5sm8nLRmlq9iRwnxbOvGJsyll9cQayUHaNQA+JOxu1VspxOzG01QXWI02Y 7z+GViVRmtH8KCqt/eqrf5Vf4X2T0sLv7vQGbT8CcwhrCiteAV8j/i/PGzAkaHDH THo33wAqu9t/eDWxIpebvQHBUEWSeeHIyn0wA9jRLRBVi1kJSVW/Wjv9PrU54wln sYp9zNQYO64HeMtGGuOP2+8mFW0HHNgQMfQEtkoTauFDpzQnIBk= =oC9O -----END PGP SIGNATURE----- --=_3317caf2e94c14a573bd9e0b5c0e31e1--
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