summaryrefslogtreecommitdiffstats
path: root/nsprpub/pr/src/io/prfdcach.c
diff options
context:
space:
mode:
Diffstat (limited to 'nsprpub/pr/src/io/prfdcach.c')
-rw-r--r--nsprpub/pr/src/io/prfdcach.c230
1 files changed, 230 insertions, 0 deletions
diff --git a/nsprpub/pr/src/io/prfdcach.c b/nsprpub/pr/src/io/prfdcach.c
new file mode 100644
index 000000000..17b71fe6b
--- /dev/null
+++ b/nsprpub/pr/src/io/prfdcach.c
@@ -0,0 +1,230 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "primpl.h"
+
+#include <string.h>
+
+/*****************************************************************************/
+/*****************************************************************************/
+/************************** File descriptor caching **************************/
+/*****************************************************************************/
+/*****************************************************************************/
+
+/*
+** This code is built into debuggable versions of NSPR to assist in
+** finding misused file descriptors. Since file descritors (PRFileDesc)
+** are identified by a pointer to their structure, they can be the
+** target of dangling references. Furthermore, NSPR caches and tries
+** to aggressively reuse file descriptors, leading to more ambiguity.
+** The following code will allow a debugging client to set environment
+** variables and control the number of file descriptors that will be
+** preserved before they are recycled. The environment variables are
+** NSPR_FD_CACHE_SIZE_LOW and NSPR_FD_CACHE_SIZE_HIGH. The former sets
+** the number of descriptors NSPR will allocate before beginning to
+** recycle. The latter is the maximum number permitted in the cache
+** (exclusive of those in use) at a time.
+*/
+typedef struct _PR_Fd_Cache
+{
+ PRLock *ml;
+ PRIntn count;
+ PRFileDesc *head, *tail;
+ PRIntn limit_low, limit_high;
+} _PR_Fd_Cache;
+
+static _PR_Fd_Cache _pr_fd_cache;
+
+
+/*
+** Get a FileDescriptor from the cache if one exists. If not allocate
+** a new one from the heap.
+*/
+PRFileDesc *_PR_Getfd(void)
+{
+ PRFileDesc *fd;
+ /*
+ ** $$$
+ ** This may look a little wasteful. We'll see. Right now I want to
+ ** be able to toggle between caching and not at runtime to measure
+ ** the differences. If it isn't too annoying, I'll leave it in.
+ ** $$$$
+ **
+ ** The test is against _pr_fd_cache.limit_high. If that's zero,
+ ** we're not doing the extended cache but going for performance.
+ */
+ if (0 == _pr_fd_cache.limit_high)
+ {
+ goto allocate;
+ }
+ else
+ {
+ do
+ {
+ if (NULL == _pr_fd_cache.head) goto allocate; /* nothing there */
+ if (_pr_fd_cache.count < _pr_fd_cache.limit_low) goto allocate;
+
+ /* we "should" be able to extract an fd from the cache */
+ PR_Lock(_pr_fd_cache.ml); /* need the lock to do this safely */
+ fd = _pr_fd_cache.head; /* protected extraction */
+ if (NULL == fd) /* unexpected, but not fatal */
+ {
+ PR_ASSERT(0 == _pr_fd_cache.count);
+ PR_ASSERT(NULL == _pr_fd_cache.tail);
+ }
+ else
+ {
+ _pr_fd_cache.count -= 1;
+ _pr_fd_cache.head = fd->higher;
+ if (NULL == _pr_fd_cache.head)
+ {
+ PR_ASSERT(0 == _pr_fd_cache.count);
+ _pr_fd_cache.tail = NULL;
+ }
+ PR_ASSERT(&_pr_faulty_methods == fd->methods);
+ PR_ASSERT(PR_INVALID_IO_LAYER == fd->identity);
+ PR_ASSERT(_PR_FILEDESC_FREED == fd->secret->state);
+ }
+ PR_Unlock(_pr_fd_cache.ml);
+
+ } while (NULL == fd); /* then go around and allocate a new one */
+ }
+
+finished:
+ fd->dtor = NULL;
+ fd->lower = fd->higher = NULL;
+ fd->identity = PR_NSPR_IO_LAYER;
+ memset(fd->secret, 0, sizeof(PRFilePrivate));
+ return fd;
+
+allocate:
+ fd = PR_NEW(PRFileDesc);
+ if (NULL != fd)
+ {
+ fd->secret = PR_NEW(PRFilePrivate);
+ if (NULL == fd->secret) PR_DELETE(fd);
+ }
+ if (NULL != fd) goto finished;
+ else return NULL;
+
+} /* _PR_Getfd */
+
+/*
+** Return a file descriptor to the cache unless there are too many in
+** there already. If put in cache, clear the fields first.
+*/
+void _PR_Putfd(PRFileDesc *fd)
+{
+ PR_ASSERT(PR_NSPR_IO_LAYER == fd->identity);
+ fd->methods = &_pr_faulty_methods;
+ fd->identity = PR_INVALID_IO_LAYER;
+ fd->secret->state = _PR_FILEDESC_FREED;
+
+ if (0 != _pr_fd_cache.limit_high)
+ {
+ if (_pr_fd_cache.count < _pr_fd_cache.limit_high)
+ {
+ PR_Lock(_pr_fd_cache.ml);
+ if (NULL == _pr_fd_cache.tail)
+ {
+ PR_ASSERT(0 == _pr_fd_cache.count);
+ PR_ASSERT(NULL == _pr_fd_cache.head);
+ _pr_fd_cache.head = _pr_fd_cache.tail = fd;
+ }
+ else
+ {
+ PR_ASSERT(NULL == _pr_fd_cache.tail->higher);
+ _pr_fd_cache.tail->higher = fd;
+ _pr_fd_cache.tail = fd; /* new value */
+ }
+ fd->higher = NULL; /* always so */
+ _pr_fd_cache.count += 1; /* count the new entry */
+ PR_Unlock(_pr_fd_cache.ml);
+ return;
+ }
+ }
+
+ PR_Free(fd->secret);
+ PR_Free(fd);
+} /* _PR_Putfd */
+
+PR_IMPLEMENT(PRStatus) PR_SetFDCacheSize(PRIntn low, PRIntn high)
+{
+ /*
+ ** This can be called at any time, may adjust the cache sizes,
+ ** turn the caches off, or turn them on. It is not dependent
+ ** on the compilation setting of DEBUG.
+ */
+ if (!_pr_initialized) _PR_ImplicitInitialization();
+
+ if (low > high) low = high; /* sanity check the params */
+
+ PR_Lock(_pr_fd_cache.ml);
+ _pr_fd_cache.limit_high = high;
+ _pr_fd_cache.limit_low = low;
+ PR_Unlock(_pr_fd_cache.ml);
+ return PR_SUCCESS;
+} /* PR_SetFDCacheSize */
+
+void _PR_InitFdCache(void)
+{
+ /*
+ ** The fd caching is enabled by default for DEBUG builds,
+ ** disabled by default for OPT builds. That default can
+ ** be overridden at runtime using environment variables
+ ** or a super-wiz-bang API.
+ */
+ const char *low = PR_GetEnv("NSPR_FD_CACHE_SIZE_LOW");
+ const char *high = PR_GetEnv("NSPR_FD_CACHE_SIZE_HIGH");
+
+ /*
+ ** _low is allowed to be zero, _high is not.
+ ** If _high is zero, we're not doing the caching.
+ */
+
+ _pr_fd_cache.limit_low = 0;
+#if defined(DEBUG)
+ _pr_fd_cache.limit_high = FD_SETSIZE;
+#else
+ _pr_fd_cache.limit_high = 0;
+#endif /* defined(DEBUG) */
+
+ if (NULL != low) _pr_fd_cache.limit_low = atoi(low);
+ if (NULL != high) _pr_fd_cache.limit_high = atoi(high);
+
+ if (_pr_fd_cache.limit_low < 0)
+ _pr_fd_cache.limit_low = 0;
+ if (_pr_fd_cache.limit_low > FD_SETSIZE)
+ _pr_fd_cache.limit_low = FD_SETSIZE;
+
+ if (_pr_fd_cache.limit_high > FD_SETSIZE)
+ _pr_fd_cache.limit_high = FD_SETSIZE;
+
+ if (_pr_fd_cache.limit_high < _pr_fd_cache.limit_low)
+ _pr_fd_cache.limit_high = _pr_fd_cache.limit_low;
+
+ _pr_fd_cache.ml = PR_NewLock();
+ PR_ASSERT(NULL != _pr_fd_cache.ml);
+
+} /* _PR_InitFdCache */
+
+void _PR_CleanupFdCache(void)
+{
+ PRFileDesc *fd, *next;
+
+ for (fd = _pr_fd_cache.head; fd != NULL; fd = next)
+ {
+ next = fd->higher;
+ PR_DELETE(fd->secret);
+ PR_DELETE(fd);
+ }
+ _pr_fd_cache.head = NULL;
+ _pr_fd_cache.tail = NULL;
+ _pr_fd_cache.count = 0;
+ PR_DestroyLock(_pr_fd_cache.ml);
+ _pr_fd_cache.ml = NULL;
+} /* _PR_CleanupFdCache */
+
+/* prfdcach.c */