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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/.)
58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
/*-
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* Copyright (c) 2003 Alan L. Cox <alc@cs.rice.edu>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _MACHINE_SF_BUF_H_
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#define _MACHINE_SF_BUF_H_
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#include <sys/queue.h>
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struct vm_page;
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struct sf_buf {
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LIST_ENTRY(sf_buf) list_entry; /* list of buffers */
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struct vm_page *m; /* currently mapped page */
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vm_offset_t kva; /* va of mapping */
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int ref_count; /* usage of this mapping */
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};
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static __inline vm_offset_t
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sf_buf_kva(struct sf_buf *sf)
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{
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return (sf->kva);
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}
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static __inline struct vm_page *
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sf_buf_page(struct sf_buf *sf)
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{
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return (sf->m);
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}
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#endif /* !_MACHINE_SF_BUF_H_ */
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