source: branches/samba-3.3.x/source/modules/vfs_cacheprime.c@ 206

Last change on this file since 206 was 206, checked in by Herwig Bauernfeind, 17 years ago

Import Samba 3.3 branch at 3.0.0 level (psmedley's port)
File size: 6.5 KB
RevLine 
[206]1/*
2 * Copyright (c) James Peach 2005-2006
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 3 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18#include "includes.h"
19
20/* Cache priming module.
21 *
22 * The purpose of this module is to do RAID stripe width reads to prime the
23 * buffer cache to do zero-copy I/O for subsequent sendfile calls. The idea is
24 * to do a single large read at the start of the file to make sure that most or
25 * all of the file is pulled into the buffer cache. Subsequent I/Os have
26 * reduced latency.
27 *
28 * Tunables.
29 *
30 * cacheprime:rsize Amount of readahead in bytes. This should be a
31 * multiple of the RAID stripe width.
32 * cacheprime:debug Debug level at which to emit messages.
33 */
34
35#define READAHEAD_MIN (128 * 1024) /* min is 128 KiB */
36#define READAHEAD_MAX (100 * 1024 * 1024) /* max is 100 MiB */
37
38#define MODULE "cacheprime"
39
40static int module_debug;
41static ssize_t g_readsz = 0;
42static void * g_readbuf = NULL;
43
44/* Prime the kernel buffer cache with data from the specified file. We use
45 * per-fsp data to make sure we only ever do this once. If pread is being
46 * emulated by seek/read/seek, when this will suck quite a lot.
47 */
48static bool prime_cache(
49 struct vfs_handle_struct * handle,
50 files_struct * fsp,
51 SMB_OFF_T offset,
52 size_t count)
53{
54 SMB_OFF_T * last;
55 ssize_t nread;
56
57 last = (SMB_OFF_T *)VFS_ADD_FSP_EXTENSION(handle, fsp, SMB_OFF_T);
58 if (!last) {
59 return False;
60 }
61
62 if (*last == -1) {
63 /* Readahead disabled. */
64 return False;
65 }
66
67 if ((*last + g_readsz) > (offset + count)) {
68 /* Skip readahead ... we've already been here. */
69 return False;
70 }
71
72 DEBUG(module_debug,
73 ("%s: doing readahead of %lld bytes at %lld for %s\n",
74 MODULE, (long long)g_readsz, (long long)*last,
75 fsp->fsp_name));
76
77 nread = sys_pread(fsp->fh->fd, g_readbuf, g_readsz, *last);
78 if (nread < 0) {
79 *last = -1;
80 return False;
81 }
82
83 *last += nread;
84 return True;
85}
86
87static int cprime_connect(
88 struct vfs_handle_struct * handle,
89 const char * service,
90 const char * user)
91{
92 module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
93 if (g_readbuf) {
94 /* Only allocate g_readbuf once. If the config changes and
95 * another client multiplexes onto this smbd, we don't want
96 * to risk memory corruption.
97 */
98 return SMB_VFS_NEXT_CONNECT(handle, service, user);
99 }
100
101 g_readsz = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
102 MODULE, "rsize", NULL));
103
104 if (g_readsz < READAHEAD_MIN) {
105 DEBUG(module_debug, ("%s: %ld bytes of readahead "
106 "requested, using minimum of %u\n",
107 MODULE, (long)g_readsz, READAHEAD_MIN));
108 g_readsz = READAHEAD_MIN;
109 } else if (g_readsz > READAHEAD_MAX) {
110 DEBUG(module_debug, ("%s: %ld bytes of readahead "
111 "requested, using maximum of %u\n",
112 MODULE, (long)g_readsz, READAHEAD_MAX));
113 g_readsz = READAHEAD_MAX;
114 }
115
116 if ((g_readbuf = SMB_MALLOC(g_readsz)) == NULL) {
117 /* Turn off readahead if we can't get a buffer. */
118 g_readsz = 0;
119 }
120
121 return SMB_VFS_NEXT_CONNECT(handle, service, user);
122}
123
124static ssize_t cprime_sendfile(
125 struct vfs_handle_struct * handle,
126 int tofd,
127 files_struct * fromfsp,
128 const DATA_BLOB * header,
129 SMB_OFF_T offset,
130 size_t count)
131{
132 if (g_readbuf && offset == 0) {
133 prime_cache(handle, fromfsp, offset, count);
134 }
135
136 return SMB_VFS_NEXT_SENDFILE(handle, tofd, fromfsp,
137 header, offset, count);
138}
139
140static ssize_t cprime_read(
141 vfs_handle_struct * handle,
142 files_struct * fsp,
143 void * data,
144 size_t count)
145{
146 SMB_OFF_T offset;
147
148 offset = SMB_VFS_LSEEK(fsp, 0, SEEK_CUR);
149 if (offset >= 0 && g_readbuf) {
150 prime_cache(handle, fsp, offset, count);
151 SMB_VFS_LSEEK(fsp, offset, SEEK_SET);
152 }
153
154 return SMB_VFS_NEXT_READ(handle, fsp, data, count);
155}
156
157static ssize_t cprime_pread(
158 vfs_handle_struct * handle,
159 files_struct * fsp,
160 void * data,
161 size_t count,
162 SMB_OFF_T offset)
163{
164 if (g_readbuf) {
165 prime_cache(handle, fsp, offset, count);
166 }
167
168 return SMB_VFS_NEXT_PREAD(handle, fsp, data, count, offset);
169}
170
171static vfs_op_tuple cprime_ops [] =
172{
173 {SMB_VFS_OP(cprime_sendfile),
174 SMB_VFS_OP_SENDFILE, SMB_VFS_LAYER_TRANSPARENT},
175 {SMB_VFS_OP(cprime_pread),
176 SMB_VFS_OP_PREAD, SMB_VFS_LAYER_TRANSPARENT},
177 {SMB_VFS_OP(cprime_read),
178 SMB_VFS_OP_READ, SMB_VFS_LAYER_TRANSPARENT},
179 {SMB_VFS_OP(cprime_connect),
180 SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
181
182 {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
183};
184
185/* -------------------------------------------------------------------------
186 * Samba module initialisation entry point.
187 * -------------------------------------------------------------------------
188 */
189
190NTSTATUS vfs_cacheprime_init(void);
191NTSTATUS vfs_cacheprime_init(void)
192{
193 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE, cprime_ops);
194}
195
196/* vim: set sw=4 ts=4 tw=79 et: */
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