xref: /freebsd/sys/kern/subr_sfbuf.c (revision 4d846d260e2b9a3d4d0a701462568268cbfe7a5b)
1 /*-
2  * Copyright (c) 2014 Gleb Smirnoff <glebius@FreeBSD.org>
3  * Copyright (c) 2003, 2005 Alan L. Cox <alc@cs.rice.edu>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  */
27 
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30 
31 #include <sys/param.h>
32 #include <sys/kernel.h>
33 #include <sys/lock.h>
34 #include <sys/malloc.h>
35 #include <sys/mutex.h>
36 #include <sys/proc.h>
37 #include <sys/sf_buf.h>
38 #include <sys/smp.h>
39 #include <sys/sysctl.h>
40 
41 #include <vm/vm.h>
42 #include <vm/vm_extern.h>
43 #include <vm/vm_page.h>
44 
45 #ifndef NSFBUFS
46 #define	NSFBUFS		(512 + maxusers * 16)
47 #endif
48 
49 static int nsfbufs;
50 static int nsfbufspeak;
51 static int nsfbufsused;
52 
53 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufs, CTLFLAG_RDTUN, &nsfbufs, 0,
54     "Maximum number of sendfile(2) sf_bufs available");
55 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufspeak, CTLFLAG_RD, &nsfbufspeak, 0,
56     "Number of sendfile(2) sf_bufs at peak usage");
57 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufsused, CTLFLAG_RD, &nsfbufsused, 0,
58     "Number of sendfile(2) sf_bufs in use");
59 
60 static void	sf_buf_init(void *arg);
61 SYSINIT(sock_sf, SI_SUB_MBUF, SI_ORDER_ANY, sf_buf_init, NULL);
62 
63 LIST_HEAD(sf_head, sf_buf);
64 
65 /*
66  * A hash table of active sendfile(2) buffers
67  */
68 static struct sf_head *sf_buf_active;
69 static u_long sf_buf_hashmask;
70 
71 #define	SF_BUF_HASH(m)	(((m) - vm_page_array) & sf_buf_hashmask)
72 
73 static TAILQ_HEAD(, sf_buf) sf_buf_freelist;
74 static u_int	sf_buf_alloc_want;
75 
76 /*
77  * A lock used to synchronize access to the hash table and free list
78  */
79 static struct mtx sf_buf_lock;
80 
81 /*
82  * Allocate a pool of sf_bufs (sendfile(2) or "super-fast" if you prefer. :-))
83  */
84 static void
85 sf_buf_init(void *arg)
86 {
87 	struct sf_buf *sf_bufs;
88 	vm_offset_t sf_base;
89 	int i;
90 
91 	if (PMAP_HAS_DMAP)
92 		return;
93 
94 	nsfbufs = NSFBUFS;
95 	TUNABLE_INT_FETCH("kern.ipc.nsfbufs", &nsfbufs);
96 
97 	sf_buf_active = hashinit(nsfbufs, M_TEMP, &sf_buf_hashmask);
98 	TAILQ_INIT(&sf_buf_freelist);
99 	sf_base = kva_alloc(nsfbufs * PAGE_SIZE);
100 	sf_bufs = malloc(nsfbufs * sizeof(struct sf_buf), M_TEMP,
101 	    M_WAITOK | M_ZERO);
102 	for (i = 0; i < nsfbufs; i++) {
103 		sf_bufs[i].kva = sf_base + i * PAGE_SIZE;
104 		TAILQ_INSERT_TAIL(&sf_buf_freelist, &sf_bufs[i], free_entry);
105 	}
106 	sf_buf_alloc_want = 0;
107 	mtx_init(&sf_buf_lock, "sf_buf", NULL, MTX_DEF);
108 }
109 
110 /*
111  * Get an sf_buf from the freelist.  May block if none are available.
112  */
113 struct sf_buf *
114 sf_buf_alloc(struct vm_page *m, int flags)
115 {
116 	struct sf_head *hash_list;
117 	struct sf_buf *sf;
118 	int error;
119 
120 	if (PMAP_HAS_DMAP)
121 		return ((struct sf_buf *)m);
122 
123 	KASSERT(curthread->td_pinned > 0 || (flags & SFB_CPUPRIVATE) == 0,
124 	    ("sf_buf_alloc(SFB_CPUPRIVATE): curthread not pinned"));
125 	hash_list = &sf_buf_active[SF_BUF_HASH(m)];
126 	mtx_lock(&sf_buf_lock);
127 	LIST_FOREACH(sf, hash_list, list_entry) {
128 		if (sf->m == m) {
129 			sf->ref_count++;
130 			if (sf->ref_count == 1) {
131 				TAILQ_REMOVE(&sf_buf_freelist, sf, free_entry);
132 				nsfbufsused++;
133 				nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
134 			}
135 #if defined(SMP) && defined(SFBUF_CPUSET)
136 			sf_buf_shootdown(sf, flags);
137 #endif
138 			goto done;
139 		}
140 	}
141 	while ((sf = TAILQ_FIRST(&sf_buf_freelist)) == NULL) {
142 		if (flags & SFB_NOWAIT)
143 			goto done;
144 		sf_buf_alloc_want++;
145 		SFSTAT_INC(sf_allocwait);
146 		error = msleep(&sf_buf_freelist, &sf_buf_lock,
147 		    (flags & SFB_CATCH) ? PCATCH | PVM : PVM, "sfbufa", 0);
148 		sf_buf_alloc_want--;
149 
150 		/*
151 		 * If we got a signal, don't risk going back to sleep.
152 		 */
153 		if (error)
154 			goto done;
155 	}
156 	TAILQ_REMOVE(&sf_buf_freelist, sf, free_entry);
157 	if (sf->m != NULL)
158 		LIST_REMOVE(sf, list_entry);
159 	LIST_INSERT_HEAD(hash_list, sf, list_entry);
160 	sf->ref_count = 1;
161 	sf->m = m;
162 	nsfbufsused++;
163 	nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
164 	sf_buf_map(sf, flags);
165 done:
166 	mtx_unlock(&sf_buf_lock);
167 	return (sf);
168 }
169 
170 /*
171  * Remove a reference from the given sf_buf, adding it to the free
172  * list when its reference count reaches zero.  A freed sf_buf still,
173  * however, retains its virtual-to-physical mapping until it is
174  * recycled or reactivated by sf_buf_alloc(9).
175  */
176 void
177 sf_buf_free(struct sf_buf *sf)
178 {
179 
180 	if (PMAP_HAS_DMAP)
181 		return;
182 
183 	mtx_lock(&sf_buf_lock);
184 	sf->ref_count--;
185 	if (sf->ref_count == 0) {
186 		TAILQ_INSERT_TAIL(&sf_buf_freelist, sf, free_entry);
187 		nsfbufsused--;
188 		if (sf_buf_unmap(sf)) {
189 			sf->m = NULL;
190 			LIST_REMOVE(sf, list_entry);
191 		}
192 		if (sf_buf_alloc_want > 0)
193 			wakeup(&sf_buf_freelist);
194 	}
195 	mtx_unlock(&sf_buf_lock);
196 }
197 
198 void
199 sf_buf_ref(struct sf_buf *sf)
200 {
201 
202 	if (PMAP_HAS_DMAP)
203 		return;
204 
205 	mtx_lock(&sf_buf_lock);
206 	KASSERT(sf->ref_count > 0, ("%s: sf %p not allocated", __func__, sf));
207 	sf->ref_count++;
208 	mtx_unlock(&sf_buf_lock);
209 }
210 
211 #ifdef SFBUF_PROCESS_PAGE
212 /*
213  * Run callback function on sf_buf that holds a certain page.
214  */
215 boolean_t
216 sf_buf_process_page(vm_page_t m, void (*cb)(struct sf_buf *))
217 {
218 	struct sf_head *hash_list;
219 	struct sf_buf *sf;
220 
221 	hash_list = &sf_buf_active[SF_BUF_HASH(m)];
222 	mtx_lock(&sf_buf_lock);
223 	LIST_FOREACH(sf, hash_list, list_entry) {
224 		if (sf->m == m) {
225 			cb(sf);
226 			mtx_unlock(&sf_buf_lock);
227 			return (TRUE);
228 		}
229 	}
230 	mtx_unlock(&sf_buf_lock);
231 	return (FALSE);
232 }
233 #endif	/* SFBUF_PROCESS_PAGE */
234