s3:smbprofile: Replace sysv shmem with tdb

What?

This patch gets rid of the central shared memory segment referenced by
"profile_p". Instead, every smbd gets a static profile_area where it collects
profiling data. Once a second, every smbd writes this profiling data into a
record of its own in a "smbprofile.tdb". smbstatus -P does a tdb_traverse on this
database and sums up what it finds.

Why?

At least in my perception sysv IPC has not the best reputation on earth. The
code before this patch uses shmat(). Samba ages ago has developed a good
abstraction of shared memory: It's called tdb.

The main reason why I started this is that I have a request to become
more flexible with profiling data. Samba should be able to collect data
per share or per user, something which is almost impossible to do with
a fixed structure. My idea is to for example install a profile area per
share and every second marshall this into one tdb record indexed by share
name. smbstatus -P would then also collect the data and either aggregate
them or put them into individual per-share statistics. This flexibility
in the data model is not really possible with one fixed structure.

But isn't it slow?

Well, I don't think so. I can't really prove it, but I do believe that on large
boxes atomically incrementing a shared memory value for every SMB does show up
due to NUMA effects. With this patch the hot code path is completely
process-local. Once a second every smbd writes into a central tdb, this of
course does atomic operations. But it's once a second, not on every SMB2 read.

There's two places where I would like to improve things: With the current code
all smbds wake up once a second. With 10,000 potentially idle smbds this will
become noticable. That's why the current only starts the timer when something has
changed.

The second place is the tdb traverse: Right now traverse is blocking in the
sense that when it has to switch hash chains it will block. With mutexes, this
means a syscall. I have a traverse light in mind that works as follows: It
assumes a locked hash chain and then walks the complete chain in one run
without unlocking in between. This way the caller can do nonblocking locks in
the first round and only do blocking locks in a second round. Also, a lot of
syscall overhead will vanish. This way smbstatus -P will have almost zero
impact on normal operations.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

1 files changed, 99 insertions, 17 deletions

diff --git a/source3/include/smbprofile.h b/source3/include/smbprofile.h
index bf2b3b456f..b32d938306 100644
--- a/source3/include/smbprofile.h
+++ b/source3/include/smbprofile.h
@@ -21,6 +21,8 @@
 
 */
 
+struct tevent_context;
+
 #ifdef WITH_PROFILE
 
 #define SMBPROFILE_STATS_ALL_SECTIONS \
@@ -322,6 +324,8 @@ struct smbprofile_stats_iobytes_async {
 };
 
 struct profile_stats {
+	uint64_t magic;
+	struct {
 #define SMBPROFILE_STATS_START
 #define SMBPROFILE_STATS_SECTION_START(name, display)
 #define SMBPROFILE_STATS_COUNT(name) \
@@ -346,11 +350,13 @@ struct profile_stats {
 #undef SMBPROFILE_STATS_IOBYTES
 #undef SMBPROFILE_STATS_SECTION_END
 #undef SMBPROFILE_STATS_END
+	} values;
 };
 
 #define _SMBPROFILE_COUNT_INCREMENT(_stats, _area, _v) do { \
-	if (do_profile_flag) { \
-		(_area)->_stats.count += (_v); \
+	if (smbprofile_state.config.do_count) { \
+		(_area)->values._stats.count += (_v); \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 #define SMBPROFILE_COUNT_INCREMENT(_name, _area, _v) \
@@ -361,7 +367,7 @@ struct profile_stats {
 #define _SMBPROFILE_TIME_ASYNC_START(_stats, _area, _async) do { \
 	(_async) = (struct smbprofile_stats_time_async) {}; \
 	if (smbprofile_state.config.do_times) { \
-		(_async).stats = &((_area)->_stats), \
+		(_async).stats = &((_area)->values._stats), \
 		(_async).start = profile_timestamp(); \
 	} \
 } while(0)
@@ -371,6 +377,7 @@ struct profile_stats {
 	if ((_async).start != 0) { \
 		(_async).stats->time += profile_timestamp() - (_async).start; \
 		(_async) = (struct smbprofile_stats_basic_async) {}; \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 
@@ -378,12 +385,13 @@ struct profile_stats {
 	struct smbprofile_stats_basic_async _async_name;
 #define _SMBPROFILE_BASIC_ASYNC_START(_stats, _area, _async) do { \
 	(_async) = (struct smbprofile_stats_basic_async) {}; \
-	if (do_profile_flag) { \
-		if (do_profile_times) { \
+	if (smbprofile_state.config.do_count) { \
+		if (smbprofile_state.config.do_times) { \
 			(_async).start = profile_timestamp(); \
-			(_async).stats = &((_area)->_stats); \
+			(_async).stats = &((_area)->values._stats); \
 		} \
-		(_area)->_stats.count += 1; \
+		(_area)->values._stats.count += 1; \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 #define SMBPROFILE_BASIC_ASYNC_START(_name, _area, _async) \
@@ -392,12 +400,13 @@ struct profile_stats {
 	if ((_async).start != 0) { \
 		(_async).stats->time += profile_timestamp() - (_async).start; \
 		(_async) = (struct smbprofile_stats_basic_async) {}; \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 
 #define _SMBPROFILE_TIMER_ASYNC_START(_stats, _area, _async) do { \
-	(_async).stats = &((_area)->_stats); \
-	if (do_profile_times) { \
+	(_async).stats = &((_area)->values._stats); \
+	if (smbprofile_state.config.do_times) { \
 		(_async).start = profile_timestamp(); \
 	} \
 } while(0)
@@ -427,10 +436,11 @@ struct profile_stats {
 	struct smbprofile_stats_bytes_async _async_name;
 #define _SMBPROFILE_BYTES_ASYNC_START(_stats, _area, _async, _bytes) do { \
 	(_async) = (struct smbprofile_stats_bytes_async) {}; \
-	if (do_profile_flag) { \
+	if (smbprofile_state.config.do_count) { \
 		_SMBPROFILE_TIMER_ASYNC_START(_stats, _area, _async); \
-		(_area)->_stats.count += 1; \
-		(_area)->_stats.bytes += (_bytes); \
+		(_area)->values._stats.count += 1; \
+		(_area)->values._stats.bytes += (_bytes); \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 #define SMBPROFILE_BYTES_ASYNC_START(_name, _area, _async, _bytes) \
@@ -443,6 +453,7 @@ struct profile_stats {
 	if ((_async).stats != NULL) { \
 		_SMBPROFILE_TIMER_ASYNC_END(_async); \
 		(_async) = (struct smbprofile_stats_bytes_async) {}; \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 
@@ -450,10 +461,11 @@ struct profile_stats {
 	struct smbprofile_stats_iobytes_async _async_name;
 #define _SMBPROFILE_IOBYTES_ASYNC_START(_stats, _area, _async, _inbytes) do { \
 	(_async) = (struct smbprofile_stats_iobytes_async) {}; \
-	if (do_profile_flag) { \
+	if (smbprofile_state.config.do_count) { \
 		_SMBPROFILE_TIMER_ASYNC_START(_stats, _area, _async); \
-		(_area)->_stats.count += 1; \
-		(_area)->_stats.inbytes += (_inbytes); \
+		(_area)->values._stats.count += 1; \
+		(_area)->values._stats.inbytes += (_inbytes); \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 #define SMBPROFILE_IOBYTES_ASYNC_START(_name, _area, _async, _inbytes) \
@@ -467,12 +479,62 @@ struct profile_stats {
 		(_async).stats->outbytes += (_outbytes); \
 		_SMBPROFILE_TIMER_ASYNC_END(_async); \
 		(_async) = (struct smbprofile_stats_iobytes_async) {}; \
+		smbprofile_dump_schedule(); \
 	} \
 } while(0)
 
 extern struct profile_stats *profile_p;
-extern bool do_profile_flag;
-extern bool do_profile_times;
+
+struct smbprofile_global_state {
+	struct {
+		struct tdb_wrap *db;
+		struct tevent_context *ev;
+		struct tevent_timer *te;
+	} internal;
+
+	struct {
+		bool do_count;
+		bool do_times;
+	} config;
+
+	struct {
+		struct profile_stats global;
+	} stats;
+};
+
+extern struct smbprofile_global_state smbprofile_state;
+
+void smbprofile_dump_schedule_timer(void);
+void smbprofile_dump_setup(struct tevent_context *ev);
+
+static inline void smbprofile_dump_schedule(void)
+{
+	if (likely(smbprofile_state.internal.te != NULL)) {
+		return;
+	}
+
+	if (unlikely(smbprofile_state.internal.ev == NULL)) {
+		return;
+	}
+
+	smbprofile_dump_schedule_timer();
+}
+
+static inline bool smbprofile_dump_pending(void)
+{
+	if (smbprofile_state.internal.te == NULL) {
+		return false;
+	}
+
+	return true;
+}
+
+void smbprofile_dump(void);
+
+void smbprofile_cleanup(pid_t pid);
+void smbprofile_stats_accumulate(struct profile_stats *acc,
+				 const struct profile_stats *add);
+void smbprofile_collect(struct profile_stats *stats);
 
 static inline uint64_t profile_timestamp(void)
 {
@@ -531,6 +593,26 @@ static inline uint64_t profile_timestamp(void)
 #define END_PROFILE(x)
 #define END_PROFILE_BYTES(x)
 
+static inline bool smbprofile_dump_pending(void)
+{
+	return false;
+}
+
+static inline void smbprofile_dump_setup(struct tevent_context *ev)
+{
+	return;
+}
+
+static inline void smbprofile_dump(void)
+{
+	return;
+}
+
+static inline void smbprofile_cleanup(pid_t pid)
+{
+	return;
+}
+
 #endif /* WITH_PROFILE */
 
 /* The following definitions come from profile/profile.c  */