2 * Copyright (c) James Peach 2005-2006
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 2 of the License, or
7 * (at your option) any later version.
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.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 /* Cache priming module.
23 * The purpose of this module is to do RAID stripe width reads to prime the
24 * buffer cache to do zero-copy I/O for subsequent sendfile calls. The idea is
25 * to do a single large read at the start of the file to make sure that most or
26 * all of the file is pulled into the buffer cache. Subsequent I/Os have
31 * cacheprime:rsize Amount of readahead in bytes. This should be a
32 * multiple of the RAID stripe width.
33 * cacheprime:debug Debug level at which to emit messages.
36 #define READAHEAD_MIN (128 * 1024) /* min is 128 KiB */
37 #define READAHEAD_MAX (100 * 1024 * 1024) /* max is 100 MiB */
39 #define MODULE "cacheprime"
41 static int module_debug
;
42 static ssize_t g_readsz
= 0;
43 static void * g_readbuf
= NULL
;
45 /* Prime the kernel buffer cache with data from the specified file. We use
46 * per-fsp data to make sure we only ever do this once. If pread is being
47 * emulated by seek/read/seek, when this will suck quite a lot.
49 static BOOL
prime_cache(
50 struct vfs_handle_struct
* handle
,
59 last
= VFS_ADD_FSP_EXTENSION(handle
, fsp
, SMB_OFF_T
);
65 /* Readahead disabled. */
69 if ((*last
+ g_readsz
) > (offset
+ count
)) {
70 /* Skip readahead ... we've already been here. */
75 ("%s: doing readahead of %lld bytes at %lld for %s\n",
76 MODULE
, (long long)g_readsz
, (long long)*last
,
79 nread
= sys_pread(fd
, g_readbuf
, g_readsz
, *last
);
89 static int cprime_connect(
90 struct vfs_handle_struct
* handle
,
94 module_debug
= lp_parm_int(SNUM(handle
->conn
), MODULE
, "debug", 100);
96 /* Only allocate g_readbuf once. If the config changes and
97 * another client multiplexes onto this smbd, we don't want
98 * to risk memory corruption.
100 return SMB_VFS_NEXT_CONNECT(handle
, service
, user
);
103 g_readsz
= conv_str_size(lp_parm_const_string(SNUM(handle
->conn
),
104 MODULE
, "rsize", NULL
));
106 if (g_readsz
< READAHEAD_MIN
) {
107 DEBUG(module_debug
, ("%s: %ld bytes of readahead "
108 "requested, using minimum of %u\n",
109 MODULE
, (long)g_readsz
, READAHEAD_MIN
));
110 g_readsz
= READAHEAD_MIN
;
111 } else if (g_readsz
> READAHEAD_MAX
) {
112 DEBUG(module_debug
, ("%s: %ld bytes of readahead "
113 "requested, using maximum of %u\n",
114 MODULE
, (long)g_readsz
, READAHEAD_MAX
));
115 g_readsz
= READAHEAD_MAX
;
118 if ((g_readbuf
= SMB_MALLOC(g_readsz
)) == NULL
) {
119 /* Turn off readahead if we can't get a buffer. */
123 return SMB_VFS_NEXT_CONNECT(handle
, service
, user
);
126 static ssize_t
cprime_sendfile(
127 struct vfs_handle_struct
* handle
,
131 const DATA_BLOB
* header
,
135 if (g_readbuf
&& offset
== 0) {
136 prime_cache(handle
, fsp
, fromfd
, offset
, count
);
139 return SMB_VFS_NEXT_SENDFILE(handle
, tofd
, fsp
, fromfd
,
140 header
, offset
, count
);
143 static ssize_t
cprime_read(
144 vfs_handle_struct
* handle
,
152 offset
= SMB_VFS_LSEEK(fsp
, fd
, 0, SEEK_CUR
);
153 if (offset
>= 0 && g_readbuf
) {
154 prime_cache(handle
, fsp
, fd
, offset
, count
);
155 SMB_VFS_LSEEK(fsp
, fd
, offset
, SEEK_SET
);
158 return SMB_VFS_NEXT_READ(handle
, fsp
, fd
, data
, count
);
161 static ssize_t
cprime_pread(
162 vfs_handle_struct
* handle
,
170 prime_cache(handle
, fsp
, fd
, offset
, count
);
173 return SMB_VFS_NEXT_PREAD(handle
, fsp
, fd
, data
, count
, offset
);
176 static vfs_op_tuple cprime_ops
[] =
178 {SMB_VFS_OP(cprime_sendfile
),
179 SMB_VFS_OP_SENDFILE
, SMB_VFS_LAYER_TRANSPARENT
},
180 {SMB_VFS_OP(cprime_pread
),
181 SMB_VFS_OP_PREAD
, SMB_VFS_LAYER_TRANSPARENT
},
182 {SMB_VFS_OP(cprime_read
),
183 SMB_VFS_OP_READ
, SMB_VFS_LAYER_TRANSPARENT
},
184 {SMB_VFS_OP(cprime_connect
),
185 SMB_VFS_OP_CONNECT
, SMB_VFS_LAYER_TRANSPARENT
},
187 {SMB_VFS_OP(NULL
), SMB_VFS_OP_NOOP
, SMB_VFS_LAYER_NOOP
}
190 /* -------------------------------------------------------------------------
191 * Samba module initialisation entry point.
192 * -------------------------------------------------------------------------
195 NTSTATUS
vfs_cacheprime_init(void)
197 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION
, MODULE
, cprime_ops
);
200 /* vim: set sw=4 ts=4 tw=79 et: */