Date: Sun, 17 Mar 2013 20:11:09 +0000 (UTC) From: Eitan Adler <eadler@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r248442 - projects/counters/share/man/man9 Message-ID: <201303172011.r2HKB9ks035252@svn.freebsd.org>
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Author: eadler Date: Sun Mar 17 20:11:08 2013 New Revision: 248442 URL: http://svnweb.freebsd.org/changeset/base/248442 Log: Content and English language changes Discussed with: glebius, jilles, kib Approved by: glebius (implicit) Modified: projects/counters/share/man/man9/counter.9 Modified: projects/counters/share/man/man9/counter.9 ============================================================================== --- projects/counters/share/man/man9/counter.9 Sun Mar 17 19:27:14 2013 (r248441) +++ projects/counters/share/man/man9/counter.9 Sun Mar 17 20:11:08 2013 (r248442) @@ -99,14 +99,15 @@ Subtract value of from .Nm .Fa cnt . -The API does not guarantee any protection from underflow. +The KPI does not guarantee any protection from underflow. See .Sx IMPLEMENTATION DETAILS . .It Fn counter_u64_fetch cnt Obtain current snapshot of the data collected in .Nm .Fa cnt . -The data obtained is not guaranteed to be precise. +The data obtained is not guaranteed to reflect the real cumulative +value for any moment. .It Fn counter_u64_zero cnt Clear data collected in .Nm @@ -140,8 +141,9 @@ Any write to oid zeroes it. .Sh IMPLEMENTATION DETAILS On all architectures .Nm -is implemented using per-CPU data fields, that are specially aligned in -memory, to avoid excessive CPU cache invalidation during updates. +is implemented using per-CPU data fields that are specially aligned +in memory, to avoid inter-CPU bus traffic due to shared use +of the variables between CPUs. These are allocated using .Va UMA_ZONE_PCPU .Xr uma 9
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