-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 8/1/14 8:59 PM, Justin T. Gibbs wrote: > On Aug 1, 2014, at 4:33 PM, Xin LI <delp...@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, -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJT3JboAAoJEJW2GBstM+nsq7wP/j+QfLnkTVTIgFWk15L2haeo V6lPD2GwjggxGn50S9+POOiB1V4kZwTEydkEJ+4vMXkH+Evke5p0eYObF7Ye1ejc UqprnIuEK3N63YkbX2tNkIX22zCJd5KKvnHjWd7IR88c2XT2doPwo+o9IsaWFdrW Gn2FYr1hsw3Pi5PKytzEhc1zOpBa/kXy6gy9ZDOjBCnUXjL6v29GlOa5L+VLCOtG mGpiVdWl18unLW+x0uoT4AfDVeyNYJGIDMzzV5OBtLp14fcDCcWPswwpq4VMDdrf ZWLarOahwpjD7eO9MHFMXgtrZVzj7qY3xXJJDsiNWv109TwOvHx9NmYAVtP3CT3g T5QrkXJzuWJlIsBAX1bHtdLMRRAdSTDN8q9XE3r+2TJ1NUpazEEkA7iRpXLrlvbP rEyFGjr3CEKdGQXMdGx3kpqgqYLRAdo3MdXQIXU/OpWY3CAqm82ljQtqHmfuDHO1 Kb5rcqLxApKaxGqoq7GnZH5vHfrU9ulaYBBTykV3PyCGV5A4p4FWUJBUaS/FaKZv +w53o87L+LRPniyPU5V6i18I/M2X3mIGzUCv+i5oK7ac0O5hMOkORXVs8KTiQ7DG zCzw2eUG26cDGDGPzpixvVKPBKqFTDROQIttmtm5x234zESFINtS534Hdl+XAsDh zSVHaNCcebZ0RYiphbd3 =fb7k -----END PGP SIGNATURE----- _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
