diff --git a/README b/README
index 2f68e14..4f2c4a7 100644
--- a/README
+++ b/README
@@ -1,3 +1,40 @@
+This is an Nginx fork that adds dtrace USDT probes.
 
-Documentation is available at http://nginx.org
+This is still under development and not usable yet.
+
+Installation:
+
+    ./configure --with-dtrace-probes \
+        --with-dtrace=/usr/sbin/dtrace \
+        ...
+    make
+    make install
+
+Usage on Linux (with systemtap):
+
+    # make the stap-nginx script visiable in your PATH
+    export PATH=/usr/local/nginx/sbin:$PATH
+
+    # list all the static probes available in your nginx
+    stap-nginx -L 'process("nginx").mark("*")'
+
+    # run the test.stp file
+    stap-nginx test.stp
+
+Sample test.stp file:
+
+    probe begin
+    {
+        print("Tracing.  Hit CTRL-C to stop.\n")
+    }
+
+    probe process("nginx").mark("http-subrequest-start")
+    {
+        printf("uri: %s?%s\n", ngx_http_req_uri($arg1),
+            ngx_http_req_args($arg1))
+    }
+
+For now, only tested on Solaris 11 Express and Fedora Linux 17.
+
+The original Nginx documentation is available at http://nginx.org
 
diff --git a/auto/install b/auto/install
index 254f9bc..0252fef 100644
--- a/auto/install
+++ b/auto/install
@@ -16,6 +16,20 @@ END
 fi
 
 
+case ".$NGX_STAP_NGX_PATH" in
+    ./*)
+    ;;
+
+    .)
+        NGX_STAP_NGX_PATH=$NGX_PREFIX/sbin/stap-nginx
+    ;;
+
+    *)
+        NGX_STAP_NGX_PATH=$NGX_PREFIX/$NGX_STAP_NGX_PATH
+    ;;
+esac
+
+
 case ".$NGX_SBIN_PATH" in
     ./*)
     ;;
@@ -53,6 +67,16 @@ case ".$NGX_PID_PATH" in
 esac
 
 
+case ".$NGX_TAPSET_PREFIX" in
+    ./* | .)
+    ;;
+
+    *)
+        NGX_TAPSET_PREFIX=$NGX_PREFIX/$NGX_TAPSET_PREFIX
+    ;;
+esac
+
+
 case ".$NGX_ERROR_LOG_PATH" in
     ./* | .)
     ;;
@@ -151,6 +175,36 @@ install:	$NGX_OBJS${ngx_dirsep}nginx${ngx_binext} \
 		|| cp -R $NGX_HTML '\$(DESTDIR)$NGX_PREFIX'
 END
 
+if [ $NGX_DTRACE = YES -a $DTRACE_FROM_SYSTEMTAP = YES ]; then
+
+    ngx_tapset_srcs="$NGX_TAPSET_SRCS"
+
+        cat << END                                            >> $NGX_MAKEFILE
+	test -d '\$(DESTDIR)$NGX_TAPSET_PREFIX' || \
+		mkdir -p '\$(DESTDIR)$NGX_TAPSET_PREFIX'
+END
+
+    for ngx_tapset_src in $ngx_tapset_srcs
+    do
+        ngx_tapset_file=`basename $ngx_tapset_src`
+
+        cat << END                                            >> $NGX_MAKEFILE
+
+	sed -e "s|NGX_SBIN_PATH|$NGX_SBIN_PATH|g" $ngx_long_cont \
+                $ngx_tapset_src > '\$(DESTDIR)$NGX_TAPSET_PREFIX/$ngx_tapset_file'
+END
+
+    done
+
+    cat << END                                                >> $NGX_MAKEFILE
+
+	test -d '\$(DESTDIR)`dirname "$NGX_STAP_NGX_PATH"`' || \
+		mkdir -p '\$(DESTDIR)`dirname "$NGX_STAP_NGX_PATH"`'
+	cp $NGX_OBJS/stap-nginx '\$(DESTDIR)$NGX_STAP_NGX_PATH'
+	chmod 0755 '\$(DESTDIR)$NGX_STAP_NGX_PATH'
+END
+
+fi
 
 if test -n "$NGX_ERROR_LOG_PATH"; then
     cat << END                                                >> $NGX_MAKEFILE
@@ -162,6 +216,18 @@ END
 fi
 
 
+if [ $NGX_DTRACE = YES ]; then
+    cat << END                                                >> $NGX_MAKEFILE
+
+$NGX_OBJS${ngx_dirsep}stap-nginx: src/dtrace/stap-nginx
+	sed -e "s|NGX_TAPSET_PREFIX|$NGX_TAPSET_PREFIX|g" $ngx_long_cont \
+            -e "s|NGX_SBIN_DIR|`dirname $NGX_SBIN_PATH`|g" $ngx_long_cont \
+            -e "s|NGX_SBIN_PATH|$NGX_SBIN_PATH|g" $ngx_long_cont \
+            src/dtrace/stap-nginx > $NGX_OBJS${ngx_dirsep}stap-nginx
+END
+fi
+
+
 # create Makefile
 
 cat << END >> Makefile
diff --git a/auto/make b/auto/make
index 05b7454..aa813b1 100644
--- a/auto/make
+++ b/auto/make
@@ -26,6 +26,9 @@ LINK =	$LINK
 
 END
 
+if [ $NGX_DTRACE = YES ]; then
+    echo DTRACE = $DTRACE                   >> $NGX_MAKEFILE
+fi
 
 if test -n "$NGX_PERL_CFLAGS"; then
     echo NGX_PERL_CFLAGS = $NGX_PERL_CFLAGS                   >> $NGX_MAKEFILE
@@ -177,6 +180,44 @@ ngx_objs=`echo $ngx_all_objs $ngx_modules_obj \
     | sed -e "s/  *\([^ ][^ ]*\)/$ngx_long_regex_cont\1/g" \
           -e "s/\//$ngx_regex_dirsep/g"`
 
+if [ $NGX_DTRACE = YES ]; then
+
+    ngx_dtrace_obj=$NGX_OBJS${ngx_dirsep}ngx_dtrace_provider.$ngx_objext
+
+    ngx_dtrace_h=$NGX_OBJS${ngx_dirsep}ngx_dtrace_provider.h
+
+    ngx_dtrace_d=$NGX_OBJS${ngx_dirsep}dtrace_providers.d
+
+    ngx_dtrace_providers=`echo $NGX_DTRACE_PROVIDERS \
+        | sed -e "s/  *\([^ ][^ ]*\)/$ngx_long_regex_cont\1/g" \
+              -e "s/\//$ngx_regex_dirsep/g"`
+
+    cat << END                                                >> $NGX_MAKEFILE
+
+all: $NGX_OBJS${ngx_dirsep}nginx${ngx_binext}
+
+$ngx_dtrace_d: $ngx_dtrace_providers
+	cat $ngx_dtrace_providers > $ngx_dtrace_d
+
+$ngx_dtrace_h: $ngx_dtrace_d
+	\$(DTRACE) -xnolibs -h -o $ngx_dtrace_h -s $ngx_dtrace_d
+END
+
+    if [ $DTRACE_PROBE_OBJ = YES ]; then
+        cat << END                                            >> $NGX_MAKEFILE
+$ngx_dtrace_obj: $ngx_dtrace_d $ngx_deps$ngx_spacer
+	\$(DTRACE) -xnolibs -G -o $ngx_dtrace_obj -s $ngx_dtrace_d $ngx_objs
+END
+
+        ngx_deps="$ngx_deps$ngx_long_cont$ngx_dtrace_obj"
+        ngx_objs="$ngx_objs$ngx_long_cont$ngx_dtrace_obj"
+
+        if [ "$DTRACE_FROM_SYSTEMTAP" = YES ]; then
+            ngx_deps="$ngx_deps$ngx_long_cont$NGX_OBJS${ngx_dirsep}stap-nginx"
+        fi
+    fi
+fi
+
 if test -n "$NGX_LD_OPT$CORE_LIBS"; then
     ngx_libs=`echo $NGX_LD_OPT $CORE_LIBS \
         | sed -e "s/\//$ngx_regex_dirsep/g" -e "s/^/$ngx_long_regex_cont/"`
diff --git a/auto/options b/auto/options
index 6c3a4db..8d18c01 100644
--- a/auto/options
+++ b/auto/options
@@ -12,6 +12,8 @@ NGX_CONF_PATH=
 NGX_ERROR_LOG_PATH=
 NGX_PID_PATH=
 NGX_LOCK_PATH=
+NGX_TAPSET_PREFIX=
+NGX_STAP_NGX_PATH=
 NGX_USER=
 NGX_GROUP=
 
@@ -20,6 +22,12 @@ CPP=
 NGX_OBJS=objs
 
 NGX_DEBUG=NO
+NGX_DTRACE=NO
+DTRACE=dtrace
+
+DTRACE_PROBE_OBJ=YES
+DTRACE_FROM_SYSTEMTAP=NO
+
 NGX_CC_OPT=
 NGX_LD_OPT=
 CPU=NO
@@ -170,6 +178,8 @@ do
         --error-log-path=*)              NGX_ERROR_LOG_PATH="$value";;
         --pid-path=*)                    NGX_PID_PATH="$value"      ;;
         --lock-path=*)                   NGX_LOCK_PATH="$value"     ;;
+        --tapset-prefix=*)               NGX_TAPSET_PREFIX="$value" ;;
+        --stap-nginx-path=*)             NGX_STAP_NGX_PATH="$value" ;;
         --user=*)                        NGX_USER="$value"          ;;
         --group=*)                       NGX_GROUP="$value"         ;;
 
@@ -275,7 +285,8 @@ use the \"--without-http_limit_conn_module\" option instead"
         --with-ld-opt=*)                 NGX_LD_OPT="$value"        ;;
         --with-cpu-opt=*)                CPU="$value"               ;;
         --with-debug)                    NGX_DEBUG=YES              ;;
-
+        --with-dtrace=*)                 DTRACE="$value"            ;;
+        --with-dtrace-probes)            NGX_DTRACE=YES             ;;
         --without-pcre)                  USE_PCRE=DISABLED          ;;
         --with-pcre)                     USE_PCRE=YES               ;;
         --with-pcre=*)                   PCRE="$value"              ;;
@@ -329,6 +340,8 @@ cat << END
   --error-log-path=PATH              set error log pathname
   --pid-path=PATH                    set nginx.pid pathname
   --lock-path=PATH                   set nginx.lock pathname
+  --tapset-prefix=PATH               set systemtap tapset directory prefix
+  --stap-nginx-path=PATH             set stap-nginx pathname
 
   --user=USER                        set non-privileged user for
                                      worker processes
@@ -455,6 +468,8 @@ cat << END
   --with-openssl-opt=OPTIONS         set additional build options for OpenSSL
 
   --with-debug                       enable debug logging
+  --with-dtrace-probes               enable dtrace USDT probes
+  --with-dtrace=PATH                 set dtrace utility pathname
 
 END
 
@@ -484,6 +499,7 @@ NGX_CONF_PATH=${NGX_CONF_PATH:-conf/nginx.conf}
 NGX_CONF_PREFIX=`dirname $NGX_CONF_PATH`
 NGX_PID_PATH=${NGX_PID_PATH:-logs/nginx.pid}
 NGX_LOCK_PATH=${NGX_LOCK_PATH:-logs/nginx.lock}
+NGX_TAPSET_PREFIX=${NGX_TAPSET_PREFIX:-tapset}
 
 if [ ".$NGX_ERROR_LOG_PATH" = ".stderr" ]; then
     NGX_ERROR_LOG_PATH=
diff --git a/auto/os/darwin b/auto/os/darwin
index 590e036..af33cf3 100644
--- a/auto/os/darwin
+++ b/auto/os/darwin
@@ -114,3 +114,6 @@ ngx_feature_libs=
 ngx_feature_test="int32_t  lock, n;
                   n = OSAtomicCompareAndSwap32Barrier(0, 1, lock)"
 . auto/feature
+
+DTRACE_PROBE_OBJ=NO
+
diff --git a/auto/os/freebsd b/auto/os/freebsd
index 6aa823f..ee15166 100644
--- a/auto/os/freebsd
+++ b/auto/os/freebsd
@@ -142,3 +142,8 @@ if [ $version -ge 701000 ]; then
     echo " + cpuset_setaffinity() found"
     have=NGX_HAVE_CPUSET_SETAFFINITY . auto/have
 fi
+
+if [ $NGX_DTRACE = YES ]; then
+    NGX_LD_OPT="$NGX_LD_OPT -lelf"
+fi
+
diff --git a/auto/os/linux b/auto/os/linux
index c506d3d..cbbfbf1 100644
--- a/auto/os/linux
+++ b/auto/os/linux
@@ -151,3 +151,5 @@ ngx_include="sys/vfs.h";     . auto/include
 
 
 CC_AUX_FLAGS="$cc_aux_flags -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64"
+
+DTRACE_FROM_SYSTEMTAP=YES
diff --git a/auto/sources b/auto/sources
index 522d722..5e48797 100644
--- a/auto/sources
+++ b/auto/sources
@@ -36,7 +36,13 @@ CORE_DEPS="src/core/nginx.h \
            src/core/ngx_conf_file.h \
            src/core/ngx_resolver.h \
            src/core/ngx_open_file_cache.h \
-           src/core/ngx_crypt.h"
+           src/core/ngx_crypt.h \
+           src/core/ngx_core_probe.h"
+
+
+if [ $NGX_DTRACE = YES ]; then
+    CORE_DEPS="$CORE_DEPS objs/ngx_dtrace_provider.h"
+fi
 
 
 CORE_SRCS="src/core/nginx.c \
@@ -82,14 +88,15 @@ OPENSSL_SRCS=src/event/ngx_event_openssl.c
 
 EVENT_MODULES="ngx_events_module ngx_event_core_module"
 
-EVENT_INCS="src/event src/event/modules"
+EVENT_INCS="src/event src/event/modules src/http src/http/modules"
 
 EVENT_DEPS="src/event/ngx_event.h \
             src/event/ngx_event_timer.h \
             src/event/ngx_event_posted.h \
             src/event/ngx_event_busy_lock.h \
             src/event/ngx_event_connect.h \
-            src/event/ngx_event_pipe.h"
+            src/event/ngx_event_pipe.h \
+            src/event/ngx_event_probe.h"
 
 EVENT_SRCS="src/event/ngx_event.c \
             src/event/ngx_event_timer.c \
@@ -291,7 +298,8 @@ HTTP_DEPS="src/http/ngx_http.h \
            src/http/ngx_http_script.h \
            src/http/ngx_http_upstream.h \
            src/http/ngx_http_upstream_round_robin.h \
-           src/http/ngx_http_busy_lock.h"
+           src/http/ngx_http_busy_lock.h \
+           src/http/ngx_http_probe.h"
 
 HTTP_SRCS="src/http/ngx_http.c \
            src/http/ngx_http_core_module.c \
@@ -529,3 +537,8 @@ NGX_GOOGLE_PERFTOOLS_MODULE=ngx_google_perftools_module
 NGX_GOOGLE_PERFTOOLS_SRCS=src/misc/ngx_google_perftools_module.c
 
 NGX_CPP_TEST_SRCS=src/misc/ngx_cpp_test_module.cpp
+
+NGX_DTRACE_PROVIDERS=src/dtrace/nginx_provider.d
+
+NGX_TAPSET_SRCS=src/dtrace/nginx.stp
+
diff --git a/auto/summary b/auto/summary
index dcebec9..3cb269e 100644
--- a/auto/summary
+++ b/auto/summary
@@ -92,6 +92,19 @@ else
     echo "  nginx logs errors to stderr"
 fi
 
+if [ $NGX_DTRACE = YES ]; then
+    cat << END
+  nginx dtrace static probes enabled
+END
+
+    if [ $DTRACE_FROM_SYSTEMTAP = YES ]; then
+        cat << END
+  nginx systemtap tapset prefix: "$NGX_TAPSET_PREFIX"
+  nginx systemtap wrapper script: "$NGX_STAP_NGX_PATH"
+END
+    fi
+fi
+
 cat << END
   nginx http access log file: "$NGX_HTTP_LOG_PATH"
   nginx http client request body temporary files: "$NGX_HTTP_CLIENT_TEMP_PATH"
diff --git a/configure b/configure
index d7d8189..05fab87 100755
--- a/configure
+++ b/configure
@@ -23,6 +23,9 @@ if [ $NGX_DEBUG = YES ]; then
     have=NGX_DEBUG . auto/have
 fi
 
+if [ $NGX_DTRACE = YES ]; then
+    have=NGX_DTRACE . auto/have
+fi
 
 if test -z "$NGX_PLATFORM"; then
     echo "checking for OS"
diff --git a/src/core/ngx_core_probe.h b/src/core/ngx_core_probe.h
new file mode 100644
index 0000000..91bf91e
--- /dev/null
+++ b/src/core/ngx_core_probe.h
@@ -0,0 +1,25 @@
+#ifndef _NGX_CORE_PROBE_H_INCLUDED_
+#define _NGX_CORE_PROBE_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+
+
+#if (NGX_DTRACE)
+
+#include <ngx_http.h>
+#include <ngx_dtrace_provider.h>
+
+#define ngx_core_probe_create_pool_done(pool, size)                             \
+    NGINX_CREATE_POOL_DONE(pool, size)
+
+#else /* !(NGX_DTRACE) */
+
+#define ngx_core_probe_create_pool_done(pool, size)
+
+#endif
+
+
+#endif /* _NGX_CORE_PROBE_H_INCLUDED_ */
diff --git a/src/core/ngx_palloc.c b/src/core/ngx_palloc.c
index efbc244..8d81aab 100644
--- a/src/core/ngx_palloc.c
+++ b/src/core/ngx_palloc.c
@@ -7,6 +7,7 @@
 
 #include <ngx_config.h>
 #include <ngx_core.h>
+#include <ngx_core_probe.h>
 
 
 static void *ngx_palloc_block(ngx_pool_t *pool, size_t size);
@@ -37,6 +38,8 @@ ngx_create_pool(size_t size, ngx_log_t *log)
     p->cleanup = NULL;
     p->log = log;
 
+    ngx_core_probe_create_pool_done(p, size);
+
     return p;
 }
 
diff --git a/src/dtrace/nginx.stp b/src/dtrace/nginx.stp
new file mode 100644
index 0000000..4c228bd
--- /dev/null
+++ b/src/dtrace/nginx.stp
@@ -0,0 +1,288 @@
+/* tapset for nginx */
+
+
+function ngx_indent(n, delta)
+{
+    s = ""
+    for (i = 0; i < n; i++) {
+        s .= delta
+    }
+
+    return s
+}
+
+
+function ngx_http_subreq_depth(r)
+{
+    depth = 0
+
+    for (pr = @cast(r, "ngx_http_request_t", "NGX_SBIN_PATH")->parent;
+         pr != 0;
+         pr = @cast(pr, "ngx_http_request_t", "NGX_SBIN_PATH")->parent)
+    {
+        depth++
+    }
+
+    return depth
+}
+
+
+function ngx_http_req_parent(r)
+{
+    return @cast(r, "ngx_http_request_s", "NGX_SBIN_PATH")->parent
+}
+
+
+/* retrieve the request uri string from the ngx_http_request_t pointer */
+function ngx_http_req_uri(r)
+{
+    len = @cast(r, "ngx_http_request_s", "NGX_SBIN_PATH")->uri->len
+
+    if (len == 0) {
+        return ""
+    }
+
+    return user_string_n(@cast(r, "ngx_http_request_s", "NGX_SBIN_PATH")->uri->data, len)
+}
+
+
+/* retrieve the request query string from the ngx_http_request_t pointer */
+function ngx_http_req_args(r)
+{
+    len = @cast(r, "ngx_http_request_s", "NGX_SBIN_PATH")->args->len
+
+    if (len == 0) {
+        return ""
+    }
+
+    return user_string_n(@cast(r, "ngx_http_request_s", "NGX_SBIN_PATH")->args->data, len)
+}
+
+
+/* retrieve the first command name (or directive name) from
+ * the ngx_module_t pointer */
+function ngx_http_module_cmd(m)
+{
+    cmds = @cast(m, "ngx_module_t", "NGX_SBIN_PATH")->commands
+    if (cmds == 0) {
+        return ""
+    }
+
+    len = @cast(cmds, "ngx_command_t", "NGX_SBIN_PATH")->name->len
+
+    if (len == 0) {
+        return ""
+    }
+
+    return user_string_n(@cast(cmds, "ngx_command_t", "NGX_SBIN_PATH")->name->data, len)
+}
+
+
+function ngx_chain_buf(cl)
+{
+    return @cast(cl, "ngx_chain_t", "NGX_SBIN_PATH")->buf
+}
+
+
+function ngx_chain_next(cl)
+{
+    return @cast(cl, "ngx_chain_t", "NGX_SBIN_PATH")->next
+}
+
+function ngx_buf_tag(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->tag
+}
+
+function ngx_buf_in_memory(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->temporary
+        || @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->memory
+        || @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->mmap
+}
+
+
+function ngx_buf_pos(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->pos
+}
+
+
+function ngx_buf_file_pos(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->file_pos
+}
+
+
+function ngx_buf_last(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->last
+}
+
+
+function ngx_buf_file_last(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->file_last
+}
+
+
+function ngx_buf_end(b)
+{
+    return @cast(b, "ngx_buf_t", "NGX_SBIN_PATH")->end
+}
+
+
+function ngx_buf_last_buf(b)
+{
+    return @cast(b, "ngx_buf_t", "/home/agentzh/git/lua-nginx-module/work/nginx/sbin/nginx")->last_buf
+}
+
+
+function ngx_buf_last_in_chain(b)
+{
+    return @cast(b, "ngx_buf_t", "/home/agentzh/git/lua-nginx-module/work/nginx/sbin/nginx")->last_in_chain
+}
+
+
+function ngx_buf_sync(b)
+{
+    return @cast(b, "ngx_buf_t", "/home/agentzh/git/lua-nginx-module/work/nginx/sbin/nginx")->sync
+}
+
+
+function ngx_buf_flush(b)
+{
+    return @cast(b, "ngx_buf_t", "/home/agentzh/git/lua-nginx-module/work/nginx/sbin/nginx")->flush
+}
+
+
+function ngx_buf_size(b)
+{
+    if (ngx_buf_in_memory(b)) {
+        return ngx_buf_last(b) - ngx_buf_pos(b)
+    }
+
+    return ngx_buf_file_last(b) - ngx_buf_file_pos(b)
+}
+
+
+function ngx_buf_data(b)
+{
+    return user_string_n(ngx_buf_pos(b), ngx_buf_last(b) - ngx_buf_pos(b))
+}
+
+
+function ngx_chain_writer_ctx_out(ctx)
+{
+    return @cast(c, "ngx_chain_writer_ctx_t", "NGX_SBIN_PATH")->out
+}
+
+
+function ngx_chain_dump:string (input)
+{
+    if (input == 0) {
+        return "NULL"
+    }
+
+    out = ""
+    cl = input
+    while (cl) {
+        buf = ngx_chain_buf(cl)
+
+        if (ngx_buf_in_memory(buf)) {
+            out .= sprintf("[%s]", text_str(ngx_buf_data(buf)))
+
+        } else {
+            out .= "\"\""
+        }
+
+        if (ngx_buf_last_buf(buf)) {
+            out .= "<last_buf>"
+        }
+
+        if (ngx_buf_last_in_chain(buf)) {
+            out .= "<last_in_chain>"
+        }
+
+        if (ngx_buf_sync(buf)) {
+            out .= "<sync>"
+        }
+
+        if (ngx_buf_flush(buf)) {
+            out .= "<flush>"
+        }
+
+        tag = ngx_buf_tag(buf)
+        if (tag) {
+            out .= sprintf("<tag:%p>", tag)
+        }
+
+        cl = ngx_chain_next(cl)
+        if (cl) {
+            out .= " "
+        }
+    }
+    return out
+}
+
+
+function ngx_pool_cleanup_file_name(c)
+{
+    return user_string(@cast(c, "ngx_pool_cleanup_file_t", "NGX_SBIN_PATH")->name)
+}
+
+
+function ngx_http_req_content_length(r)
+{
+    return @cast(r, "ngx_http_request_t", "NGX_SBIN_PATH")->headers_in->content_length_n
+}
+
+
+function ngx_http_req_body_temp_file_name(r)
+{
+    rb = @cast(r, "ngx_http_request_t", "NGX_SBIN_PATH")->request_body
+    if (!rb) {
+        return ""
+    }
+
+    tf = @cast(rb, "ngx_http_request_body_t", "NGX_SBIN_PATH")->temp_file
+    if (!tf) {
+        return ""
+    }
+
+    len = @cast(tf, "ngx_temp_file_t", "NGX_SBIN_PATH")->file->name->len
+
+    return user_string_n(@cast(tf, "ngx_temp_file_t", "NGX_SBIN_PATH")->file->name->data, len)
+}
+
+
+function ngx_table_elt_key(e)
+{
+    len = @cast(e, "ngx_table_elt_t", "NGX_SBIN_PATH")->key->len
+
+    return user_string_n(@cast(e, "ngx_table_elt_t", "NGX_SBIN_PATH")->key->data, len)
+}
+
+
+function ngx_table_elt_value(e)
+{
+    len = @cast(e, "ngx_table_elt_t", "NGX_SBIN_PATH")->value->len
+
+    return user_string_n(@cast(e, "ngx_table_elt_t", "NGX_SBIN_PATH")->value->data, len)
+}
+
+
+function ngx_iovec_dump:string (iov, iovcnt) {
+    out = ""
+    for (i = 0; i < iovcnt; i++) {
+        out .= sprintf("\"%s\"(%p)", text_str(user_string_n(
+                @cast(iov, "struct iovec")[i]->iov_base,
+                @cast(iov, "struct iovec")[i]->iov_len)
+            ), @cast(iov, "struct iovec")[i]->iov_base)
+        if (i != iovcnt - 1) {
+            out .= " "
+        }
+    }
+    return out
+}
+
diff --git a/src/dtrace/nginx_provider.d b/src/dtrace/nginx_provider.d
new file mode 100644
index 0000000..147ca12
--- /dev/null
+++ b/src/dtrace/nginx_provider.d
@@ -0,0 +1,41 @@
+typedef struct { int dummy; } ngx_http_request_t;
+typedef struct { int dummy; } ngx_str_t;
+typedef int64_t ngx_int_t;
+typedef uint64_t ngx_uint_t;
+typedef ngx_uint_t ngx_msec_t;
+typedef struct { int dummy; } ngx_module_t;
+typedef struct { int dummy; } ngx_http_module_t;
+typedef struct { int dummy; } ngx_table_elt_t;
+typedef struct { int dummy; } ngx_event_t;
+typedef struct { int dummy; } ngx_pool_t;
+typedef char unsigned u_char;
+
+
+provider nginx {
+    /* probes for subrequests */
+    probe http__subrequest__cycle(ngx_http_request_t *pr, ngx_str_t *uri, ngx_str_t *args);
+    probe http__subrequest__start(ngx_http_request_t *r);
+    probe http__subrequest__finalize_writing(ngx_http_request_t *r);
+    probe http__subrequest__finalize_nonactive(ngx_http_request_t *r);
+    probe http__subrequest__wake__parent(ngx_http_request_t *r);
+    probe http__subrequest__done(ngx_http_request_t *r);
+    probe http__subrequest__post__start(ngx_http_request_t *r, ngx_int_t rc);
+    probe http__subrequest__post__done(ngx_http_request_t *r, ngx_int_t rc);
+    probe http__module__post__config(ngx_module_t *m);
+    probe http__read__body__abort(ngx_http_request_t *r, char *reason);
+    probe http__read__body__done(ngx_http_request_t *r);
+    probe http__read__req__line__done(ngx_http_request_t *r);
+    probe http__read__req__header__done(ngx_http_request_t *r, ngx_table_elt_t *h);
+    probe timer__add(ngx_event_t *ev, ngx_msec_t timer);
+    probe timer__del(ngx_event_t *ev);
+    probe timer__expire(ngx_event_t *ev);
+    probe create__pool__done(ngx_pool_t *pool, size_t size);
+};
+
+
+#pragma D attributes Evolving/Evolving/Common      provider nginx provider
+#pragma D attributes Private/Private/Unknown       provider nginx module
+#pragma D attributes Private/Private/Unknown       provider nginx function
+#pragma D attributes Private/Private/Common        provider nginx name
+#pragma D attributes Evolving/Evolving/Common      provider nginx args
+
diff --git a/src/dtrace/stap-nginx b/src/dtrace/stap-nginx
new file mode 100755
index 0000000..1bca4cf
--- /dev/null
+++ b/src/dtrace/stap-nginx
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+PATH="NGX_SBIN_DIR:$PATH"
+export PATH
+exec stap -d "NGX_SBIN_PATH" -I "NGX_TAPSET_PREFIX" "$@"
+
diff --git a/src/event/ngx_event_probe.h b/src/event/ngx_event_probe.h
new file mode 100644
index 0000000..5aa0397
--- /dev/null
+++ b/src/event/ngx_event_probe.h
@@ -0,0 +1,33 @@
+#ifndef _NGX_EVENT_PROBE_H_INCLUDED_
+#define _NGX_EVENT_PROBE_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+
+
+#if (NGX_DTRACE)
+
+#include <ngx_http.h>
+#include <ngx_dtrace_provider.h>
+
+#define ngx_event_probe_timer_add(ev, timer)                                 \
+    NGINX_TIMER_ADD(ev, timer)
+
+#define ngx_event_probe_timer_del(ev)                                        \
+    NGINX_TIMER_DEL(ev)
+
+#define ngx_event_probe_timer_expire(ev)                                     \
+    NGINX_TIMER_EXPIRE(ev)
+
+#else /* !(NGX_DTRACE) */
+
+#define ngx_event_probe_timer_add(ev, timer)
+#define ngx_event_probe_timer_del(ev)
+#define ngx_event_probe_timer_expire(ev)
+
+#endif
+
+
+#endif /* _NGX_EVENT_PROBE_H_INCLUDED_ */
diff --git a/src/event/ngx_event_timer.c b/src/event/ngx_event_timer.c
index 177ac1c..531cccc 100644
--- a/src/event/ngx_event_timer.c
+++ b/src/event/ngx_event_timer.c
@@ -144,6 +144,8 @@ ngx_event_expire_timers(void)
             }
 #endif
 
+            ngx_event_probe_timer_expire(ev);
+
             ev->timedout = 1;
 
             ev->handler(ev);
diff --git a/src/event/ngx_event_timer.h b/src/event/ngx_event_timer.h
index ec9b316..6095d8c 100644
--- a/src/event/ngx_event_timer.h
+++ b/src/event/ngx_event_timer.h
@@ -12,6 +12,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_event.h>
+#include <ngx_event_probe.h>
 
 
 #define NGX_TIMER_INFINITE  (ngx_msec_t) -1
@@ -35,6 +36,8 @@ extern ngx_thread_volatile ngx_rbtree_t  ngx_event_timer_rbtree;
 static ngx_inline void
 ngx_event_del_timer(ngx_event_t *ev)
 {
+    ngx_event_probe_timer_del(ev);
+
     ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0,
                    "event timer del: %d: %M",
                     ngx_event_ident(ev->data), ev->timer.key);
@@ -85,6 +88,8 @@ ngx_event_add_timer(ngx_event_t *ev, ngx_msec_t timer)
 
     ev->timer.key = key;
 
+    ngx_event_probe_timer_add(ev, timer);
+
     ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,
                    "event timer add: %d: %M:%M",
                     ngx_event_ident(ev->data), timer, ev->timer.key);
diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
index f1f8a48..91bdd64 100644
--- a/src/http/ngx_http.c
+++ b/src/http/ngx_http.c
@@ -8,6 +8,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_http.h>
+#include <ngx_http_probe.h>
 
 
 static char *ngx_http_block(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
@@ -307,6 +308,9 @@ ngx_http_block(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
         module = ngx_modules[m]->ctx;
 
         if (module->postconfiguration) {
+
+            ngx_http_probe_module_post_config(ngx_modules[m]);
+
             if (module->postconfiguration(cf) != NGX_OK) {
                 return NGX_CONF_ERROR;
             }
diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index e02a251..6371fbc 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -8,6 +8,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_http.h>
+#include <ngx_http_probe.h>
 
 
 typedef struct {
@@ -2377,6 +2378,8 @@ ngx_http_subrequest(ngx_http_request_t *r,
     r->main->subrequests--;
 
     if (r->main->subrequests == 0) {
+        ngx_http_probe_subrequest_cycle(r, uri, args);
+
         ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                       "subrequests cycle while processing \"%V\"", uri);
         r->main->subrequests = 1;
@@ -2489,6 +2492,8 @@ ngx_http_subrequest(ngx_http_request_t *r,
 
     *psr = sr;
 
+    ngx_http_probe_subrequest_start(sr);
+
     return ngx_http_post_request(sr, NULL);
 }
 
diff --git a/src/http/ngx_http_probe.h b/src/http/ngx_http_probe.h
new file mode 100644
index 0000000..d7d2d45
--- /dev/null
+++ b/src/http/ngx_http_probe.h
@@ -0,0 +1,75 @@
+#ifndef _NGX_HTTP_PROBE_H_INCLUDED_
+#define _NGX_HTTP_PROBE_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+#if (NGX_DTRACE)
+
+#include <ngx_dtrace_provider.h>
+
+#define ngx_http_probe_subrequest_cycle(pr, uri, args)                       \
+    NGINX_HTTP_SUBREQUEST_CYCLE(pr, uri, args)
+
+#define ngx_http_probe_subrequest_start(r)                                   \
+    NGINX_HTTP_SUBREQUEST_START(r)
+
+#define ngx_http_probe_subrequest_finalize_writing(r)                        \
+    NGINX_HTTP_SUBREQUEST_FINALIZE_WRITING(r)
+
+#define ngx_http_probe_subrequest_finalize_nonactive(r)                      \
+    NGINX_HTTP_SUBREQUEST_FINALIZE_NONACTIVE(r)
+
+#define ngx_http_probe_subrequest_finalize_nonactive(r)                      \
+    NGINX_HTTP_SUBREQUEST_FINALIZE_NONACTIVE(r)
+
+#define ngx_http_probe_subrequest_wake_parent(r)                             \
+    NGINX_HTTP_SUBREQUEST_WAKE_PARENT(r)
+
+#define ngx_http_probe_subrequest_done(r)                                    \
+    NGINX_HTTP_SUBREQUEST_DONE(r)
+
+#define ngx_http_probe_subrequest_post_start(r, rc)                          \
+    NGINX_HTTP_SUBREQUEST_POST_START(r, rc)
+
+#define ngx_http_probe_subrequest_post_done(r, rc)                           \
+    NGINX_HTTP_SUBREQUEST_POST_DONE(r, rc)
+
+#define ngx_http_probe_module_post_config(m)                                 \
+    NGINX_HTTP_MODULE_POST_CONFIG(m)
+
+#define ngx_http_probe_read_body_abort(r, reason)                            \
+    NGINX_HTTP_READ_BODY_ABORT(r, reason)
+
+#define ngx_http_probe_read_body_done(r)                                     \
+    NGINX_HTTP_READ_BODY_DONE(r)
+
+#define ngx_http_probe_read_req_line_done(r)                                 \
+    NGINX_HTTP_READ_REQ_LINE_DONE(r)
+
+#define ngx_http_probe_read_req_header_done(r, h)                               \
+    NGINX_HTTP_READ_REQ_HEADER_DONE(r, h)
+
+#else /* !(NGX_DTRACE) */
+
+#define ngx_http_probe_subrequest_cycle(pr, uri, args)
+#define ngx_http_probe_subrequest_start(r)
+#define ngx_http_probe_subrequest_finalize_writing(r)
+#define ngx_http_probe_subrequest_finalize_nonactive(r)
+#define ngx_http_probe_subrequest_wake_parent(r)
+#define ngx_http_probe_subrequest_done(r)
+#define ngx_http_probe_subrequest_post_start(r, rc)
+#define ngx_http_probe_subrequest_post_done(r, rc)
+#define ngx_http_probe_module_post_config(m)
+#define ngx_http_probe_read_body_abort(r, reason)
+#define ngx_http_probe_read_body_done(r)
+#define ngx_http_probe_read_req_line_done(r)
+#define ngx_http_probe_read_req_header_done(r, h)
+
+#endif /* NGX_DTRACE */
+
+
+#endif /* _NGX_HTTP_PROBE_H_INCLUDED_ */
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index ee00fd3..441b5cc 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -8,6 +8,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_http.h>
+#include <ngx_http_probe.h>
 
 
 static void ngx_http_init_request(ngx_event_t *ev);
@@ -861,6 +862,8 @@ ngx_http_process_request_line(ngx_event_t *rev)
             }
 #endif
 
+            ngx_http_probe_read_req_line_done(r);
+
             ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                            "http request line: \"%V\"", &r->request_line);
 
@@ -1108,6 +1111,8 @@ ngx_http_process_request_headers(ngx_event_t *rev)
                 return;
             }
 
+            ngx_http_probe_read_req_header_done(r, h);
+
             ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                            "http header: \"%V: %V\"",
                            &h->key, &h->value);
@@ -1958,7 +1963,11 @@ ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
     }
 
     if (r != r->main && r->post_subrequest) {
+        ngx_http_probe_subrequest_post_start(r, rc);
+
         rc = r->post_subrequest->handler(r, r->post_subrequest->data, rc);
+
+        ngx_http_probe_subrequest_post_done(r, rc);
     }
 
     if (rc == NGX_ERROR
@@ -2008,6 +2017,8 @@ ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
 
         if (r->buffered || r->postponed) {
 
+            ngx_http_probe_subrequest_finalize_writing(r);
+
             if (ngx_http_set_write_handler(r) != NGX_OK) {
                 ngx_http_terminate_request(r, 0);
             }
@@ -2044,10 +2055,14 @@ ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
                 pr->postponed = pr->postponed->next;
             }
 
+            ngx_http_probe_subrequest_done(r);
+
             c->data = pr;
 
         } else {
 
+            ngx_http_probe_subrequest_finalize_nonactive(r);
+
             ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                            "http finalize non-active request: \"%V?%V\"",
                            &r->uri, &r->args);
@@ -2059,6 +2074,8 @@ ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
             }
         }
 
+        ngx_http_probe_subrequest_wake_parent(r);
+
         if (ngx_http_post_request(pr, NULL) != NGX_OK) {
             r->main->count++;
             ngx_http_terminate_request(r, 0);
diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
index 3c69d05..89858d0 100644
--- a/src/http/ngx_http_request_body.c
+++ b/src/http/ngx_http_request_body.c
@@ -8,6 +8,7 @@
 #include <ngx_config.h>
 #include <ngx_core.h>
 #include <ngx_http.h>
+#include <ngx_http_probe.h>
 
 
 static void ngx_http_read_client_request_body_handler(ngx_http_request_t *r);
@@ -40,11 +41,15 @@ ngx_http_read_client_request_body(ngx_http_request_t *r,
     r->main->count++;
 
     if (r->request_body || r->discard_body) {
+        ngx_http_probe_read_body_abort(r,
+                                       r->request_body ? "body exists"
+                                                       : "body discarded");
         post_handler(r);
         return NGX_OK;
     }
 
     if (ngx_http_test_expect(r) != NGX_OK) {
+        ngx_http_probe_read_body_abort(r, "test expect failed");
         rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
         goto done;
     }
@@ -58,6 +63,7 @@ ngx_http_read_client_request_body(ngx_http_request_t *r,
     r->request_body = rb;
 
     if (r->headers_in.content_length_n < 0) {
+        ngx_http_probe_read_body_abort(r, "no content length");
         post_handler(r);
         return NGX_OK;
     }
@@ -68,11 +74,14 @@ ngx_http_read_client_request_body(ngx_http_request_t *r,
 
         if (r->request_body_in_file_only) {
             if (ngx_http_write_request_body(r, NULL) != NGX_OK) {
+                ngx_http_probe_read_body_abort(r, "create temp file failed");
                 rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
                 goto done;
             }
         }
 
+        ngx_http_probe_read_body_done(r);
+
         post_handler(r);
 
         return NGX_OK;
@@ -130,11 +139,14 @@ ngx_http_read_client_request_body(ngx_http_request_t *r,
 
             if (r->request_body_in_file_only) {
                 if (ngx_http_write_request_body(r, rb->bufs) != NGX_OK) {
+                    ngx_http_probe_read_body_abort(r, "write temp file failed");
                     rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
                     goto done;
                 }
             }
 
+            ngx_http_probe_read_body_done(r);
+
             post_handler(r);
 
             return NGX_OK;
@@ -239,6 +251,7 @@ ngx_http_read_client_request_body_handler(ngx_http_request_t *r)
     ngx_int_t  rc;
 
     if (r->connection->read->timedout) {
+        ngx_http_probe_read_body_abort(r, "timed out");
         r->connection->timedout = 1;
         ngx_http_finalize_request(r, NGX_HTTP_REQUEST_TIME_OUT);
         return;
@@ -273,6 +286,7 @@ ngx_http_do_read_client_request_body(ngx_http_request_t *r)
             if (rb->buf->last == rb->buf->end) {
 
                 if (ngx_http_write_request_body(r, rb->to_write) != NGX_OK) {
+                    ngx_http_probe_read_body_abort(r, "write temp file failed");
                     return NGX_HTTP_INTERNAL_SERVER_ERROR;
                 }
 
@@ -296,6 +310,9 @@ ngx_http_do_read_client_request_body(ngx_http_request_t *r)
             }
 
             if (n == 0) {
+
+                ngx_http_probe_read_body_abort(r, "connection closed");
+
                 ngx_log_error(NGX_LOG_INFO, c->log, 0,
                               "client prematurely closed connection");
             }
@@ -346,6 +363,7 @@ ngx_http_do_read_client_request_body(ngx_http_request_t *r)
         /* save the last part */
 
         if (ngx_http_write_request_body(r, rb->to_write) != NGX_OK) {
+            ngx_http_probe_read_body_abort(r, "write temp file failed");
             return NGX_HTTP_INTERNAL_SERVER_ERROR;
         }
 
@@ -375,6 +393,8 @@ ngx_http_do_read_client_request_body(ngx_http_request_t *r)
 
     r->read_event_handler = ngx_http_block_reading;
 
+    ngx_http_probe_read_body_done(r);
+
     rb->post_handler(r);
 
     return NGX_OK;
