Date: Sat, 2 Aug 2014 01:51:56 -0600 From: "Justin T. Gibbs" <gibbs@scsiguy.com> To: d@delphij.net Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Xin LI <delphij@freebsd.org>, "mav >> Alexander Motin" <mav@ixsystems.com> Subject: Re: svn commit: r269404 - head/sys/cddl/compat/opensolaris/sys Message-ID: <BBEAFAEA-DADA-4741-9AF2-10B1FF3BC17D@scsiguy.com> In-Reply-To: <53DC96E9.9020805@delphij.net> References: <201408012233.s71MXNIx051919@svn.freebsd.org> <57D656EF-5D6B-428B-9DCE-7FA360B1407F@scsiguy.com> <53DC96E9.9020805@delphij.net>
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[-- Attachment #1 --] On Aug 2, 2014, at 1:44 AM, Xin Li <delphij@delphij.net> wrote: > Signed PGP part > On 8/1/14 8:59 PM, Justin T. Gibbs wrote: > > On Aug 1, 2014, at 4:33 PM, Xin LI <delphij@freebsd.org> wrote: > > > >> Author: delphij Date: Fri Aug 1 22:33:23 2014 New Revision: > >> 269404 URL: http://svnweb.freebsd.org/changeset/base/269404 > >> > >> Log: Split gethrtime() and gethrtime_waitfree() and make the > >> former use nanouptime() instead of getnanouptime(). > >> nanouptime(9) provides more precise result at expense of being > >> slower. > >> > >> In r269223, gethrtime() is used as creation time of dbuf, which > >> in turn acts as portion of lookup key to maintain AVL invariant > >> where there can not be duplicate items. Before this change, > >> gethrtime() have preferred better execution time by sacrificing > >> precision, which may lead to panic on busy systems with: > >> > >> panic: avl_find() succeeded inside avl_add() > > > > I don’t believe that r269223 requires a temporal ordering of the > > dbufs in the AVL, just unique entries. So why use an expensive > > operation like getting high resolution time? Can’t we just use a > > PCPU counter and tag the dbufs with "CPU# << 48 | PCPU_counter”? > > What do you think about D521? (Alexander suggested similar > implementation). > > https://phabric.freebsd.org/D521 > > Cheers, Seems reasonable to me. — Justin [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQEcBAEBAgAGBQJT3JipAAoJED9n8CuvaSf4OrIIAIgaHjhkdbFyBf1gO7xIIeAj iV4Ylsv3spZtzF8S3QIpdKgQzCjA1FWcMnKE2DV7INWU5AnHU3vsw0UyCCefId1I nhru8VEh66L2YekUfDWPSydtJYdvhHI6oQFFh7hFjrBXgpBLdk4QwAP+IebegKYf 9DnukM4F508KldjedulqcIPPkzrXpArMxC4rFLtGXsYQGYZgM/R6Hj5mYFDFiZQB Tcf3mSE8/q9NrKiyZZFDKDdj6ta/kvLEopNiLR4d/K1fb7QBK6gVaLrNHRIZWRp5 dAJ8iFYPopj89AmyuX9eblT48lEIT7wScyyVvyi4LWGHdL0GUiCYWtTLMwtfM0U= =mJml -----END PGP SIGNATURE-----help
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