diff options
Diffstat (limited to 'nsprpub/pr/src/io/prfdcach.c')
| -rw-r--r-- | nsprpub/pr/src/io/prfdcach.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/nsprpub/pr/src/io/prfdcach.c b/nsprpub/pr/src/io/prfdcach.c new file mode 100644 index 0000000000..ecfe3d39cc --- /dev/null +++ b/nsprpub/pr/src/io/prfdcach.c @@ -0,0 +1,252 @@ +/* -*- 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 */ |