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From: Alan Cox <alc@FreeBSD.org>
Date: Mon, 17 Nov 2003 10:22:24 -0800 (PST)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org,
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X-FreeBSD-CVS-Branch: HEAD
Subject: cvs commit: src/sys/i386/include sf_buf.h src/sys/i386/i386
 vm_machdep.c
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alc         2003/11/17 10:22:24 PST

  FreeBSD src repository

  Modified files:
    sys/i386/include     sf_buf.h 
    sys/i386/i386        vm_machdep.c 
  Log:
   - Change the i386's sf_buf implementation so that it never allocates
     more than one sf_buf for one vm_page.  To accomplish this, we add
     a global hash table mapping vm_pages to sf_bufs and a reference
     count to each sf_buf.  (This is similar to the patches for RELENG_4
     at http://www.cs.princeton.edu/~yruan/debox/.)
  
     For the uninitiated, an sf_buf is nothing more than a kernel virtual
     address that is used for temporary virtual-to-physical mappings by
     sendfile(2) and zero-copy sockets.  As such, there is no reason for
     one vm_page to have several sf_bufs mapping it.  In fact, using more
     than one sf_buf for a single vm_page increases the likelihood that
     sendfile(2) blocks, hurting throughput.
     (See http://www.cs.princeton.edu/~yruan/debox/.)
  
  Revision  Changes    Path
  1.219     +48 -26    src/sys/i386/i386/vm_machdep.c
  1.2       +2 -1      src/sys/i386/include/sf_buf.h