Date: Mon, 26 Jan 2009 02:15:22 +0000 (UTC) From: Tom Rhodes <trhodes@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r187703 - head/share/man/man7 Message-ID: <200901260215.n0Q2FMr9033462@svn.freebsd.org>
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Author: trhodes Date: Mon Jan 26 02:15:22 2009 New Revision: 187703 URL: http://svn.freebsd.org/changeset/base/187703 Log: Better description of kern.ipc.maxpipekva. Discussed with: kib Modified: head/share/man/man7/tuning.7 Modified: head/share/man/man7/tuning.7 ============================================================================== --- head/share/man/man7/tuning.7 Mon Jan 26 01:08:24 2009 (r187702) +++ head/share/man/man7/tuning.7 Mon Jan 26 02:15:22 2009 (r187703) @@ -403,13 +403,16 @@ on the system. .Pp The .Va kern.ipc.maxpipekva -loader tunable is used to set a hard limit on the amount of pageable -address space available. -This value is auto tuned by the system, but may require manual tuning -in a few rare cases. +loader tunable is used to set a hard limit on the +amount of kernel address space allocated to mapping of pipe buffers. +Use of the mapping allows the kernel to eliminate a copy of the +data from writer address space into the kernel, directly copying +the content of mapped buffer to the reader. Increasing this value to a higher setting, such as `25165824' might -improve performance on systems where pageable address space is -quickly exhausted. +improve performance on systems where space for mapping pipe buffers +is quickly exhausted. +This exhaustion is not fatal; however, and it will only cause pipes to +to fall back to use double-copy. .Pp The .Va kern.ipc.shm_use_phys
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