283 lines
9.6 KiB
C
283 lines
9.6 KiB
C
/* $NetBSD: tmpfs_pool.c,v 1.4 2005/12/11 12:24:29 christos Exp $ */
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/*
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* Copyright (c) 2005 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Julio M. Merino Vidal, developed as part of Google's Summer of Code
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* 2005 program.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Pool allocator and convenience routines for tmpfs.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: tmpfs_pool.c,v 1.4 2005/12/11 12:24:29 christos Exp $");
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#include <sys/param.h>
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#include <sys/pool.h>
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#include <uvm/uvm.h>
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#include <fs/tmpfs/tmpfs.h>
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/* --------------------------------------------------------------------- */
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void * tmpfs_pool_page_alloc(struct pool *, int);
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void tmpfs_pool_page_free(struct pool *, void *);
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/* XXX: Will go away when our pool allocator does what it has to do by
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* itself. */
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extern void* pool_page_alloc_nointr(struct pool *, int);
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extern void pool_page_free_nointr(struct pool *, void *);
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/* --------------------------------------------------------------------- */
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/*
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* tmpfs provides a custom pool allocator mostly to exactly keep track of
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* how many memory is used for each file system instance. These pools are
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* never shared across multiple mount points for the reasons described
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* below:
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*
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* - It is very easy to control how many memory is associated with a
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* given file system. tmpfs provides a custom pool allocator that
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* controls memory usage according to previously specified usage
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* limits, by simply increasing or decreasing a counter when pages
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* are allocated or released, respectively.
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*
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* If the pools were shared, we could easily end up with unaccounted
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* memory, thus taking incorrect decisions on the amount of memory
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* use. As an example to prove this point, consider two mounted
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* instances of tmpfs, one mounted on A and another one on B. Assume
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* that each memory page can hold up to four directory entries and
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* that, for each entry you create on A, you create three on B
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* afterwards. After doing this, each memory page will be holding an
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* entry from A and three for B. If you sum up all the space taken by
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* the total amount of allocated entries, rounded up to a page
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* boundary, that number will match the number of allocated pages, so
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* everything is fine.
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*
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* Now suppose we unmount B. Given that the file system has to
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* disappear, we have to delete all the directory entries attached to
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* it. But the problem is that freeing those entries will not release
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* any memory page. Instead, each page will be filled up to a 25%,
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* and the rest, a 75%, will be lost. Not lost in a strict term,
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* because the memory can be reused by new entries, but lost in the
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* sense that it is not accounted by any file system. Despite A will
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* think it is using an amount 'X' of memory, it will be really using
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* fourth times that number, thus causing mistakes when it comes to
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* decide if there is more free space for that specific instance of
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* tmpfs.
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*
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* - The number of page faults and cache misses is reduced given that all
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* entries of a given file system are stored in less pages. Note that
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* this is true because it is common to allocate and/or access many
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* entries at once on a specific file system.
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*
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* Following the example given above, listing a directory on file system
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* A could result, in the worst case scenario, in fourth times more page
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* faults if we shared the pools.
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*/
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struct pool_allocator tmpfs_pool_allocator = {
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tmpfs_pool_page_alloc,
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tmpfs_pool_page_free,
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0,
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};
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/* --------------------------------------------------------------------- */
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/*
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* Initializes the pool pointed to by tpp and associates it to the mount
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* point tmp. The size of its elements is set to size. Its wait channel
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* is derived from the string given in what and the mount point given in
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* 'tmp', which should result in a unique string among all existing pools.
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*/
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void
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tmpfs_pool_init(struct tmpfs_pool *tpp, size_t size, const char *what,
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struct tmpfs_mount *tmp)
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{
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int cnt;
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cnt = snprintf(tpp->tp_name, sizeof(tpp->tp_name),
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"%s_pool_%p", what, tmp);
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KASSERT(cnt < sizeof(tpp->tp_name));
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pool_init(&tpp->tp_pool, size, 0, 0, 0, tpp->tp_name,
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&tmpfs_pool_allocator);
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tpp->tp_mount = tmp;
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}
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/* --------------------------------------------------------------------- */
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/*
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* Destroys the pool pointed to by 'tpp'.
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*/
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void
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tmpfs_pool_destroy(struct tmpfs_pool *tpp)
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{
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pool_destroy((struct pool *)tpp);
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}
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/* --------------------------------------------------------------------- */
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void *
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tmpfs_pool_page_alloc(struct pool *pp, int flags)
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{
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void *page;
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struct tmpfs_pool *tpp;
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struct tmpfs_mount *tmp;
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tpp = (struct tmpfs_pool *)pp;
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tmp = tpp->tp_mount;
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if (TMPFS_PAGES_MAX(tmp) - tmp->tm_pages_used == 0)
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return NULL;
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tmp->tm_pages_used += 1;
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page = pool_page_alloc_nointr(pp, flags);
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KASSERT(page != NULL);
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return page;
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}
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/* --------------------------------------------------------------------- */
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void
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tmpfs_pool_page_free(struct pool *pp, void *v)
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{
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struct tmpfs_pool *tpp;
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struct tmpfs_mount *tmp;
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tpp = (struct tmpfs_pool *)pp;
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tmp = tpp->tp_mount;
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tmp->tm_pages_used -= 1;
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pool_page_free_nointr(pp, v);
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}
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/* --------------------------------------------------------------------- */
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/*
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* Initialize the string pool pointed to by 'tsp' and attach it to the
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* 'tmp' mount point.
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*/
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void
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tmpfs_str_pool_init(struct tmpfs_str_pool *tsp, struct tmpfs_mount *tmp)
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{
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tmpfs_pool_init(&tsp->tsp_pool_16, 16, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_32, 32, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_64, 64, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_128, 128, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_256, 256, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_512, 512, "str", tmp);
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tmpfs_pool_init(&tsp->tsp_pool_1024, 1024, "str", tmp);
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}
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/* --------------------------------------------------------------------- */
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/*
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* Destroy the given string pool.
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*/
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void
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tmpfs_str_pool_destroy(struct tmpfs_str_pool *tsp)
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{
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tmpfs_pool_destroy(&tsp->tsp_pool_16);
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tmpfs_pool_destroy(&tsp->tsp_pool_32);
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tmpfs_pool_destroy(&tsp->tsp_pool_64);
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tmpfs_pool_destroy(&tsp->tsp_pool_128);
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tmpfs_pool_destroy(&tsp->tsp_pool_256);
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tmpfs_pool_destroy(&tsp->tsp_pool_512);
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tmpfs_pool_destroy(&tsp->tsp_pool_1024);
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}
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/* --------------------------------------------------------------------- */
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/*
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* Allocate a new string with a minimum length of len from the 'tsp'
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* string pool. The pool can return a bigger string, but the caller must
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* not make any assumptions about the real object size.
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*/
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char *
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tmpfs_str_pool_get(struct tmpfs_str_pool *tsp, size_t len, int flags)
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{
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struct tmpfs_pool *p;
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KASSERT(len <= 1024);
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if (len <= 16) p = &tsp->tsp_pool_16;
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else if (len <= 32) p = &tsp->tsp_pool_32;
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else if (len <= 64) p = &tsp->tsp_pool_64;
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else if (len <= 128) p = &tsp->tsp_pool_128;
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else if (len <= 256) p = &tsp->tsp_pool_256;
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else if (len <= 512) p = &tsp->tsp_pool_512;
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else if (len <= 1024) p = &tsp->tsp_pool_1024;
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else {
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KASSERT(0);
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p = NULL; /* Silence compiler warnings */
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}
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return (char *)TMPFS_POOL_GET(p, flags);
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}
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/* --------------------------------------------------------------------- */
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/*
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* Destroy the str string, which was allocated from the 'tsp' string pool
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* with a length of 'len'. The length must match the one given during
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* allocation.
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*/
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void
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tmpfs_str_pool_put(struct tmpfs_str_pool *tsp, char *str, size_t len)
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{
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struct tmpfs_pool *p;
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KASSERT(len <= 1024);
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if (len <= 16) p = &tsp->tsp_pool_16;
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else if (len <= 32) p = &tsp->tsp_pool_32;
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else if (len <= 64) p = &tsp->tsp_pool_64;
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else if (len <= 128) p = &tsp->tsp_pool_128;
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else if (len <= 256) p = &tsp->tsp_pool_256;
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else if (len <= 512) p = &tsp->tsp_pool_512;
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else if (len <= 1024) p = &tsp->tsp_pool_1024;
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else {
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KASSERT(0);
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p = NULL; /* Silence compiler warnings */
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}
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TMPFS_POOL_PUT(p, str);
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}
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