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 3 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, see <http://www.gnu.org/licenses/>.
19 #include "smbd/smbd.h"
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,
58 last = (SMB_OFF_T *)VFS_ADD_FSP_EXTENSION(handle, fsp, SMB_OFF_T, NULL);
64 /* Readahead disabled. */
68 if ((*last + g_readsz) > (offset + count)) {
69 /* Skip readahead ... we've already been here. */
74 ("%s: doing readahead of %lld bytes at %lld for %s\n",
75 MODULE, (long long)g_readsz, (long long)*last,
78 nread = sys_pread(fsp->fh->fd, g_readbuf, g_readsz, *last);
88 static int cprime_connect(
89 struct vfs_handle_struct * handle,
95 module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100);
97 /* Only allocate g_readbuf once. If the config changes and
98 * another client multiplexes onto this smbd, we don't want
99 * to risk memory corruption.
101 return SMB_VFS_NEXT_CONNECT(handle, service, user);
104 ret = SMB_VFS_NEXT_CONNECT(handle, service, user);
109 g_readsz = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
110 MODULE, "rsize", NULL));
112 if (g_readsz < READAHEAD_MIN) {
113 DEBUG(module_debug, ("%s: %ld bytes of readahead "
114 "requested, using minimum of %u\n",
115 MODULE, (long)g_readsz, READAHEAD_MIN));
116 g_readsz = READAHEAD_MIN;
117 } else if (g_readsz > READAHEAD_MAX) {
118 DEBUG(module_debug, ("%s: %ld bytes of readahead "
119 "requested, using maximum of %u\n",
120 MODULE, (long)g_readsz, READAHEAD_MAX));
121 g_readsz = READAHEAD_MAX;
124 if ((g_readbuf = SMB_MALLOC(g_readsz)) == NULL) {
125 /* Turn off readahead if we can't get a buffer. */
132 static ssize_t cprime_sendfile(
133 struct vfs_handle_struct * handle,
135 files_struct * fromfsp,
136 const DATA_BLOB * header,
140 if (g_readbuf && offset == 0) {
141 prime_cache(handle, fromfsp, offset, count);
144 return SMB_VFS_NEXT_SENDFILE(handle, tofd, fromfsp,
145 header, offset, count);
148 static ssize_t cprime_read(
149 vfs_handle_struct * handle,
156 offset = SMB_VFS_LSEEK(fsp, 0, SEEK_CUR);
157 if (offset >= 0 && g_readbuf) {
158 prime_cache(handle, fsp, offset, count);
159 SMB_VFS_LSEEK(fsp, offset, SEEK_SET);
162 return SMB_VFS_NEXT_READ(handle, fsp, data, count);
165 static ssize_t cprime_pread(
166 vfs_handle_struct * handle,
173 prime_cache(handle, fsp, offset, count);
176 return SMB_VFS_NEXT_PREAD(handle, fsp, data, count, offset);
179 static struct vfs_fn_pointers vfs_cacheprime_fns = {
180 .sendfile = cprime_sendfile,
181 .pread = cprime_pread,
182 .vfs_read = cprime_read,
183 .connect_fn = cprime_connect,
186 /* -------------------------------------------------------------------------
187 * Samba module initialisation entry point.
188 * -------------------------------------------------------------------------
191 NTSTATUS vfs_cacheprime_init(void);
192 NTSTATUS vfs_cacheprime_init(void)
194 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE,
195 &vfs_cacheprime_fns);
198 /* vim: set sw=4 ts=4 tw=79 et: */