/* * Copyright (c) James Peach 2005-2006 * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, see <http://www.gnu.org/licenses/>. */ #include "includes.h" /* Cache priming module. * * The purpose of this module is to do RAID stripe width reads to prime the * buffer cache to do zero-copy I/O for subsequent sendfile calls. The idea is * to do a single large read at the start of the file to make sure that most or * all of the file is pulled into the buffer cache. Subsequent I/Os have * reduced latency. * * Tunables. * * cacheprime:rsize Amount of readahead in bytes. This should be a * multiple of the RAID stripe width. * cacheprime:debug Debug level at which to emit messages. */ #define READAHEAD_MIN (128 * 1024) /* min is 128 KiB */ #define READAHEAD_MAX (100 * 1024 * 1024) /* max is 100 MiB */ #define MODULE "cacheprime" static int module_debug; static ssize_t g_readsz = 0; static void * g_readbuf = NULL; /* Prime the kernel buffer cache with data from the specified file. We use * per-fsp data to make sure we only ever do this once. If pread is being * emulated by seek/read/seek, when this will suck quite a lot. */ static bool prime_cache( struct vfs_handle_struct * handle, files_struct * fsp, SMB_OFF_T offset, size_t count) { SMB_OFF_T * last; ssize_t nread; last = (SMB_OFF_T *)VFS_ADD_FSP_EXTENSION(handle, fsp, SMB_OFF_T); if (!last) { return False; } if (*last == -1) { /* Readahead disabled. */ return False; } if ((*last + g_readsz) > (offset + count)) { /* Skip readahead ... we've already been here. */ return False; } DEBUG(module_debug, ("%s: doing readahead of %lld bytes at %lld for %s\n", MODULE, (long long)g_readsz, (long long)*last, fsp->fsp_name)); nread = sys_pread(fsp->fh->fd, g_readbuf, g_readsz, *last); if (nread < 0) { *last = -1; return False; } *last += nread; return True; } static int cprime_connect( struct vfs_handle_struct * handle, const char * service, const char * user) { module_debug = lp_parm_int(SNUM(handle->conn), MODULE, "debug", 100); if (g_readbuf) { /* Only allocate g_readbuf once. If the config changes and * another client multiplexes onto this smbd, we don't want * to risk memory corruption. */ return SMB_VFS_NEXT_CONNECT(handle, service, user); } g_readsz = conv_str_size(lp_parm_const_string(SNUM(handle->conn), MODULE, "rsize", NULL)); if (g_readsz < READAHEAD_MIN) { DEBUG(module_debug, ("%s: %ld bytes of readahead " "requested, using minimum of %u\n", MODULE, (long)g_readsz, READAHEAD_MIN)); g_readsz = READAHEAD_MIN; } else if (g_readsz > READAHEAD_MAX) { DEBUG(module_debug, ("%s: %ld bytes of readahead " "requested, using maximum of %u\n", MODULE, (long)g_readsz, READAHEAD_MAX)); g_readsz = READAHEAD_MAX; } if ((g_readbuf = SMB_MALLOC(g_readsz)) == NULL) { /* Turn off readahead if we can't get a buffer. */ g_readsz = 0; } return SMB_VFS_NEXT_CONNECT(handle, service, user); } static ssize_t cprime_sendfile( struct vfs_handle_struct * handle, int tofd, files_struct * fromfsp, const DATA_BLOB * header, SMB_OFF_T offset, size_t count) { if (g_readbuf && offset == 0) { prime_cache(handle, fromfsp, offset, count); } return SMB_VFS_NEXT_SENDFILE(handle, tofd, fromfsp, header, offset, count); } static ssize_t cprime_read( vfs_handle_struct * handle, files_struct * fsp, void * data, size_t count) { SMB_OFF_T offset; offset = SMB_VFS_LSEEK(fsp, 0, SEEK_CUR); if (offset >= 0 && g_readbuf) { prime_cache(handle, fsp, offset, count); SMB_VFS_LSEEK(fsp, offset, SEEK_SET); } return SMB_VFS_NEXT_READ(handle, fsp, data, count); } static ssize_t cprime_pread( vfs_handle_struct * handle, files_struct * fsp, void * data, size_t count, SMB_OFF_T offset) { if (g_readbuf) { prime_cache(handle, fsp, offset, count); } return SMB_VFS_NEXT_PREAD(handle, fsp, data, count, offset); } static vfs_op_tuple cprime_ops [] = { {SMB_VFS_OP(cprime_sendfile), SMB_VFS_OP_SENDFILE, SMB_VFS_LAYER_TRANSPARENT}, {SMB_VFS_OP(cprime_pread), SMB_VFS_OP_PREAD, SMB_VFS_LAYER_TRANSPARENT}, {SMB_VFS_OP(cprime_read), SMB_VFS_OP_READ, SMB_VFS_LAYER_TRANSPARENT}, {SMB_VFS_OP(cprime_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT}, {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP} }; /* ------------------------------------------------------------------------- * Samba module initialisation entry point. * ------------------------------------------------------------------------- */ NTSTATUS vfs_cacheprime_init(void); NTSTATUS vfs_cacheprime_init(void) { return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, MODULE, cprime_ops); } /* vim: set sw=4 ts=4 tw=79 et: */