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freebsd-dev/sys/i386/include/sf_buf.h

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- Modify alpha's sf_buf implementation to use the direct virtual-to- physical mapping. - Move the sf_buf API to its own header file; make struct sf_buf's definition machine dependent. In this commit, we remove an unnecessary field from struct sf_buf on the alpha, amd64, and ia64. Ultimately, we may eliminate struct sf_buf on those architecures except as an opaque pointer that references a vm page.
2003-11-16 06:11:26 +00:00
/*-
Implement support for CPU private mappings within sf_buf_alloc().
2005-02-13 06:23:13 +00:00
* Copyright (c) 2003, 2005 Alan L. Cox <alc@cs.rice.edu>
- Modify alpha's sf_buf implementation to use the direct virtual-to- physical mapping. - Move the sf_buf API to its own header file; make struct sf_buf's definition machine dependent. In this commit, we remove an unnecessary field from struct sf_buf on the alpha, amd64, and ia64. Ultimately, we may eliminate struct sf_buf on those architecures except as an opaque pointer that references a vm page.
2003-11-16 06:11:26 +00:00
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _MACHINE_SF_BUF_H_
#define _MACHINE_SF_BUF_H_
#include <sys/queue.h>
struct vm_page;
struct sf_buf {
- 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/.)
2003-11-17 18:22:24 +00:00
LIST_ENTRY(sf_buf) list_entry; /* list of buffers */
Don't remove the virtual-to-physical mapping when an sf_buf is freed. Instead, allow the mapping to persist, but add the sf_buf to a free list. If a later sendfile(2) or zero-copy send resends the same physical page, perhaps with the same or different contents, then the mapping overhead is avoided and the sf_buf is simply removed from the free list. In other words, the i386 sf_buf implementation now behaves as a cache of virtual-to-physical translations using an LRU replacement policy on inactive sf_bufs. This is similar in concept to a part of http://www.cs.princeton.edu/~yruan/debox/ patch, but much simpler in implementation. Note: none of this is required on alpha, amd64, or ia64. They now use their direct virtual-to-physical mapping to avoid any emphemeral mapping overheads in their sf_buf implementations.
2003-12-07 22:49:25 +00:00
TAILQ_ENTRY(sf_buf) free_entry; /* list of buffers */
- Modify alpha's sf_buf implementation to use the direct virtual-to- physical mapping. - Move the sf_buf API to its own header file; make struct sf_buf's definition machine dependent. In this commit, we remove an unnecessary field from struct sf_buf on the alpha, amd64, and ia64. Ultimately, we may eliminate struct sf_buf on those architecures except as an opaque pointer that references a vm page.
2003-11-16 06:11:26 +00:00
struct vm_page *m; /* currently mapped page */
vm_offset_t kva; /* va of mapping */
- 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/.)
2003-11-17 18:22:24 +00:00
int ref_count; /* usage of this mapping */
Implement support for CPU private mappings within sf_buf_alloc().
2005-02-13 06:23:13 +00:00
#ifdef SMP
cpumask_t cpumask; /* cpus on which mapping is valid */
#endif
- Modify alpha's sf_buf implementation to use the direct virtual-to- physical mapping. - Move the sf_buf API to its own header file; make struct sf_buf's definition machine dependent. In this commit, we remove an unnecessary field from struct sf_buf on the alpha, amd64, and ia64. Ultimately, we may eliminate struct sf_buf on those architecures except as an opaque pointer that references a vm page.
2003-11-16 06:11:26 +00:00
};
static __inline vm_offset_t
sf_buf_kva(struct sf_buf *sf)
{
return (sf->kva);
}
static __inline struct vm_page *
sf_buf_page(struct sf_buf *sf)
{
return (sf->m);
}
#endif /* !_MACHINE_SF_BUF_H_ */
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