The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_sfbuf.c

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    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: releng/11.0/sys/kern/subr_sfbuf.c 269813 2014-08-11 15:06:07Z glebius $");
   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/sf_buf.h>
   37 #include <sys/smp.h>
   38 #include <sys/sysctl.h>
   39 
   40 #include <vm/vm.h>
   41 #include <vm/vm_extern.h>
   42 #include <vm/vm_page.h>
   43 
   44 #ifndef NSFBUFS
   45 #define NSFBUFS         (512 + maxusers * 16)
   46 #endif
   47 
   48 static int nsfbufs;
   49 static int nsfbufspeak;
   50 static int nsfbufsused;
   51 
   52 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufs, CTLFLAG_RDTUN, &nsfbufs, 0,
   53     "Maximum number of sendfile(2) sf_bufs available");
   54 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufspeak, CTLFLAG_RD, &nsfbufspeak, 0,
   55     "Number of sendfile(2) sf_bufs at peak usage");
   56 SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufsused, CTLFLAG_RD, &nsfbufsused, 0,
   57     "Number of sendfile(2) sf_bufs in use");
   58 
   59 static void     sf_buf_init(void *arg);
   60 SYSINIT(sock_sf, SI_SUB_MBUF, SI_ORDER_ANY, sf_buf_init, NULL);
   61 
   62 LIST_HEAD(sf_head, sf_buf);
   63 
   64 /*
   65  * A hash table of active sendfile(2) buffers
   66  */
   67 static struct sf_head *sf_buf_active;
   68 static u_long sf_buf_hashmask;
   69 
   70 #define SF_BUF_HASH(m)  (((m) - vm_page_array) & sf_buf_hashmask)
   71 
   72 static TAILQ_HEAD(, sf_buf) sf_buf_freelist;
   73 static u_int    sf_buf_alloc_want;
   74 
   75 /*
   76  * A lock used to synchronize access to the hash table and free list
   77  */
   78 static struct mtx sf_buf_lock;
   79 
   80 /*
   81  * Allocate a pool of sf_bufs (sendfile(2) or "super-fast" if you prefer. :-))
   82  */
   83 static void
   84 sf_buf_init(void *arg)
   85 {
   86         struct sf_buf *sf_bufs;
   87         vm_offset_t sf_base;
   88         int i;
   89 
   90 #ifdef SFBUF_OPTIONAL_DIRECT_MAP
   91         if (SFBUF_OPTIONAL_DIRECT_MAP)
   92                 return;
   93 #endif
   94 
   95         nsfbufs = NSFBUFS;
   96         TUNABLE_INT_FETCH("kern.ipc.nsfbufs", &nsfbufs);
   97 
   98         sf_buf_active = hashinit(nsfbufs, M_TEMP, &sf_buf_hashmask);
   99         TAILQ_INIT(&sf_buf_freelist);
  100         sf_base = kva_alloc(nsfbufs * PAGE_SIZE);
  101         sf_bufs = malloc(nsfbufs * sizeof(struct sf_buf), M_TEMP,
  102             M_WAITOK | M_ZERO);
  103         for (i = 0; i < nsfbufs; i++) {
  104                 sf_bufs[i].kva = sf_base + i * PAGE_SIZE;
  105                 TAILQ_INSERT_TAIL(&sf_buf_freelist, &sf_bufs[i], free_entry);
  106         }
  107         sf_buf_alloc_want = 0;
  108         mtx_init(&sf_buf_lock, "sf_buf", NULL, MTX_DEF);
  109 }
  110 
  111 /*
  112  * Get an sf_buf from the freelist.  May block if none are available.
  113  */
  114 struct sf_buf *
  115 sf_buf_alloc(struct vm_page *m, int flags)
  116 {
  117         struct sf_head *hash_list;
  118         struct sf_buf *sf;
  119         int error;
  120 
  121 #ifdef SFBUF_OPTIONAL_DIRECT_MAP
  122         if (SFBUF_OPTIONAL_DIRECT_MAP)
  123                 return ((struct sf_buf *)m);
  124 #endif
  125 
  126         KASSERT(curthread->td_pinned > 0 || (flags & SFB_CPUPRIVATE) == 0,
  127             ("sf_buf_alloc(SFB_CPUPRIVATE): curthread not pinned"));
  128         hash_list = &sf_buf_active[SF_BUF_HASH(m)];
  129         mtx_lock(&sf_buf_lock);
  130         LIST_FOREACH(sf, hash_list, list_entry) {
  131                 if (sf->m == m) {
  132                         sf->ref_count++;
  133                         if (sf->ref_count == 1) {
  134                                 TAILQ_REMOVE(&sf_buf_freelist, sf, free_entry);
  135                                 nsfbufsused++;
  136                                 nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
  137                         }
  138 #if defined(SMP) && defined(SFBUF_CPUSET)
  139                         sf_buf_shootdown(sf, flags);
  140 #endif
  141                         goto done;
  142                 }
  143         }
  144         while ((sf = TAILQ_FIRST(&sf_buf_freelist)) == NULL) {
  145                 if (flags & SFB_NOWAIT)
  146                         goto done;
  147                 sf_buf_alloc_want++;
  148                 SFSTAT_INC(sf_allocwait);
  149                 error = msleep(&sf_buf_freelist, &sf_buf_lock,
  150                     (flags & SFB_CATCH) ? PCATCH | PVM : PVM, "sfbufa", 0);
  151                 sf_buf_alloc_want--;
  152 
  153                 /*
  154                  * If we got a signal, don't risk going back to sleep. 
  155                  */
  156                 if (error)
  157                         goto done;
  158         }
  159         TAILQ_REMOVE(&sf_buf_freelist, sf, free_entry);
  160         if (sf->m != NULL)
  161                 LIST_REMOVE(sf, list_entry);
  162         LIST_INSERT_HEAD(hash_list, sf, list_entry);
  163         sf->ref_count = 1;
  164         sf->m = m;
  165         nsfbufsused++;
  166         nsfbufspeak = imax(nsfbufspeak, nsfbufsused);
  167         sf_buf_map(sf, flags);
  168 done:
  169         mtx_unlock(&sf_buf_lock);
  170         return (sf);
  171 }
  172 
  173 /*
  174  * Remove a reference from the given sf_buf, adding it to the free
  175  * list when its reference count reaches zero.  A freed sf_buf still,
  176  * however, retains its virtual-to-physical mapping until it is
  177  * recycled or reactivated by sf_buf_alloc(9).
  178  */
  179 void
  180 sf_buf_free(struct sf_buf *sf)
  181 {
  182 
  183 #ifdef SFBUF_OPTIONAL_DIRECT_MAP
  184         if (SFBUF_OPTIONAL_DIRECT_MAP)
  185                 return;
  186 #endif
  187 
  188         mtx_lock(&sf_buf_lock);
  189         sf->ref_count--;
  190         if (sf->ref_count == 0) {
  191                 TAILQ_INSERT_TAIL(&sf_buf_freelist, sf, free_entry);
  192                 nsfbufsused--;
  193                 if (sf_buf_unmap(sf)) {
  194                         sf->m = NULL;
  195                         LIST_REMOVE(sf, list_entry);
  196                 }
  197                 if (sf_buf_alloc_want > 0)
  198                         wakeup(&sf_buf_freelist);
  199         }
  200         mtx_unlock(&sf_buf_lock);
  201 }
  202 
  203 void
  204 sf_buf_ref(struct sf_buf *sf)
  205 {
  206 
  207 #ifdef SFBUF_OPTIONAL_DIRECT_MAP
  208         if (SFBUF_OPTIONAL_DIRECT_MAP)
  209                 return;
  210 #endif
  211 
  212         mtx_lock(&sf_buf_lock);
  213         KASSERT(sf->ref_count > 0, ("%s: sf %p not allocated", __func__, sf));
  214         sf->ref_count++;
  215         mtx_unlock(&sf_buf_lock);
  216 }
  217 
  218 #ifdef SFBUF_PROCESS_PAGE
  219 /*
  220  * Run callback function on sf_buf that holds a certain page.
  221  */
  222 boolean_t
  223 sf_buf_process_page(vm_page_t m, void (*cb)(struct sf_buf *))
  224 {
  225         struct sf_head *hash_list;
  226         struct sf_buf *sf;
  227 
  228         hash_list = &sf_buf_active[SF_BUF_HASH(m)];
  229         mtx_lock(&sf_buf_lock);
  230         LIST_FOREACH(sf, hash_list, list_entry) {
  231                 if (sf->m == m) {
  232                         cb(sf);
  233                         mtx_unlock(&sf_buf_lock);
  234                         return (TRUE);
  235                 }
  236         }
  237         mtx_unlock(&sf_buf_lock);
  238         return (FALSE);
  239 }
  240 #endif  /* SFBUF_PROCESS_PAGE */

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