82241ed55c
Currently each call to telldir() requires a malloc and adds an entry to a linked list which must be traversed on future telldir(), seekdir(), closedir(), and readdir() calls. Applications that call telldir() for every directory entry incur O(n^2) behavior in readdir() and O(n) in telldir() and closedir(). This optimization eliminates the malloc() and linked list in most cases by packing the relevant information into a single long. On 64-bit architectures msdosfs, NFS, tmpfs, UFS, and ZFS can all use the packed representation. On 32-bit architectures msdosfs, NFS, and UFS can use the packed representation, but ZFS and tmpfs can only use it for about the first 128 files per directory. Memory savings is about 50 bytes per telldir(3) call. Speedup for telldir()-heavy directory traversals is about 20-30x for one million files per directory. Reviewed by: kib, mav, mckusick MFC after: 3 weeks Sponsored by: Spectra Logic Corp Differential Revision: https://reviews.freebsd.org/D13385
113 lines
3.8 KiB
C
113 lines
3.8 KiB
C
/*-
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
*
|
|
* Copyright (c) 1983, 1993
|
|
* The Regents of the University of California. All rights reserved.
|
|
*
|
|
* Copyright (c) 2000
|
|
* Daniel Eischen. All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. Neither the name of the University nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* $FreeBSD$
|
|
*/
|
|
|
|
#ifndef _TELLDIR_H_
|
|
#define _TELLDIR_H_
|
|
|
|
#include <sys/queue.h>
|
|
#include <stdbool.h>
|
|
|
|
/*
|
|
* telldir will malloc one of these to describe the current directory position,
|
|
* if it can't fit that information into the packed structure below. It
|
|
* records the current magic cookie returned by getdirentries and the offset
|
|
* within the buffer associated with that return value.
|
|
*/
|
|
struct ddloc_mem {
|
|
LIST_ENTRY(ddloc_mem) loc_lqe; /* entry in list */
|
|
long loc_index; /* key associated with structure */
|
|
off_t loc_seek; /* magic cookie returned by getdirentries */
|
|
long loc_loc; /* offset of entry in buffer */
|
|
};
|
|
|
|
#ifdef __LP64__
|
|
#define DD_LOC_BITS 31
|
|
#define DD_SEEK_BITS 32
|
|
#define DD_INDEX_BITS 63
|
|
#else
|
|
#define DD_LOC_BITS 12
|
|
#define DD_SEEK_BITS 19
|
|
#define DD_INDEX_BITS 31
|
|
#endif
|
|
|
|
/*
|
|
* This is the real type returned by telldir. telldir will prefer to return
|
|
* the packed type, if possible, or the malloced type otherwise. For msdosfs,
|
|
* UFS, and NFS, directory positions usually fit within the packed type. For
|
|
* ZFS and tmpfs, they usually fit within the packed type on 64-bit
|
|
* architectures.
|
|
*/
|
|
union ddloc_packed {
|
|
long l; /* Opaque type returned by telldir(3) */
|
|
struct {
|
|
/* Identifies union type. Must be 0. */
|
|
unsigned long is_packed:1;
|
|
/* Index into directory's linked list of ddloc_mem */
|
|
unsigned long index:DD_INDEX_BITS;
|
|
} __packed i;
|
|
struct {
|
|
/* Identifies union type. Must be 1. */
|
|
unsigned long is_packed:1;
|
|
/* offset of entry in buffer*/
|
|
unsigned long loc:DD_LOC_BITS;
|
|
/* magic cookie returned by getdirentries */
|
|
unsigned long seek:DD_SEEK_BITS;
|
|
} __packed s;
|
|
};
|
|
|
|
_Static_assert(sizeof(long) == sizeof(union ddloc_packed),
|
|
"packed telldir size mismatch!");
|
|
|
|
/*
|
|
* One of these structures is malloced for each DIR to record telldir
|
|
* positions.
|
|
*/
|
|
struct _telldir {
|
|
LIST_HEAD(, ddloc_mem) td_locq; /* list of locations */
|
|
long td_loccnt; /* index of entry for sequential readdir's */
|
|
};
|
|
|
|
bool _filldir(DIR *, bool);
|
|
struct dirent *_readdir_unlocked(DIR *, int);
|
|
void _reclaim_telldir(DIR *);
|
|
void _seekdir(DIR *, long);
|
|
void _fixtelldir(DIR *dirp, long oldseek, long oldloc);
|
|
|
|
#define RDU_SKIP 0x0001
|
|
#define RDU_SHORT 0x0002
|
|
|
|
#endif
|