| 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 |
|
|---|
| 40 | static int module_debug;
|
|---|
| 41 | static ssize_t g_readsz = 0;
|
|---|
| 42 | static 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 | */
|
|---|
| 48 | static 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;
|
|---|
|
|---|
