Date: Sun, 19 Jul 2015 19:27:27 +0000 (UTC) From: Warren Block <wblock@FreeBSD.org> To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r47018 - head/en_US.ISO8859-1/htdocs/news/status Message-ID: <201507191927.t6JJRRed029793@repo.freebsd.org>
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Author: wblock Date: Sun Jul 19 19:27:26 2015 New Revision: 47018 URL: https://svnweb.freebsd.org/changeset/doc/47018 Log: Restore mysteriously lost portion of PCID report, add URL to repository commit. Modified: head/en_US.ISO8859-1/htdocs/news/status/report-2015-04-2015-06.xml Modified: head/en_US.ISO8859-1/htdocs/news/status/report-2015-04-2015-06.xml ============================================================================== --- head/en_US.ISO8859-1/htdocs/news/status/report-2015-04-2015-06.xml Sun Jul 19 18:50:12 2015 (r47017) +++ head/en_US.ISO8859-1/htdocs/news/status/report-2015-04-2015-06.xml Sun Jul 19 19:27:26 2015 (r47018) @@ -1085,6 +1085,11 @@ </person> </contact> + <links> + <url href="https://svnweb.freebsd.org/base?view=revision&revision=282684">Commit + r282684</url> + </links> + <body> <p>Process-Context Identifiers (PCIDs) is a feature of the Translation Lookaside Buffer (TLB) on Intel processors, @@ -1128,7 +1133,28 @@ performed. As result, the new implementation issues exactly the same amount of shootdown IPIs as pmap which does not utilize PCID.</p> + + <p>Another change included with the PCID rewrite is a move of + the address space switching code from assembler to C source, + making the algorithm easier to understand and validate.</p> + + <p>Measurements done with <tt>hwpmc(4)</tt> on a Haswell machine + indicated that the new implementation reduced the amount of + data TLB misses up to 10 times, without an impact on the IPI + counters.</p> + + <p>The rewrite was committed to HEAD at r282684.</p> + + <p>Note: AMD processors do not have PCID feature for host paging + (AMD provides ASIDs for SVM use). But it is likely that AMD + processors do cache TLB translations for different address + spaces transparently, and snoop writes to the page tables to + invalidate the caches.</p> </body> + + <sponsor> + The FreeBSD Foundation + </sponsor> </project> <project cat='proj'>
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