Date: Tue, 16 Jul 2019 03:09:04 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r350021 - head/sys/i386/i386 Message-ID: <201907160309.x6G39467059294@repo.freebsd.org>
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Author: alc Date: Tue Jul 16 03:09:03 2019 New Revision: 350021 URL: https://svnweb.freebsd.org/changeset/base/350021 Log: Revert r349973. Upon further reflection, I realized that the comment deleted by r349973 is still valid on i386. Restore it. Discussed with: markj Modified: head/sys/i386/i386/pmap.c Modified: head/sys/i386/i386/pmap.c ============================================================================== --- head/sys/i386/i386/pmap.c Mon Jul 15 23:43:38 2019 (r350020) +++ head/sys/i386/i386/pmap.c Tue Jul 16 03:09:03 2019 (r350021) @@ -5096,6 +5096,13 @@ __CONCAT(PMTYPE, ts_referenced)(vm_page_t m) * reference bit will result in clearing that bit. * This function is designed to avoid the selection of * the same 4KB page for every 2- or 4MB page mapping. + * + * On demotion, a mapping that hasn't been referenced + * is simply destroyed. To avoid the possibility of a + * subsequent page fault on a demoted wired mapping, + * always leave its reference bit set. Moreover, + * since the superpage is wired, the current state of + * its reference bit won't affect page replacement. */ if ((((pa >> PAGE_SHIFT) ^ (pv->pv_va >> PDRSHIFT) ^ (uintptr_t)pmap) & (NPTEPG - 1)) == 0 &&
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