delay-accounting: Re-implement -c for getdelays.c to report information on a target command

PATCH In review Mel Gorman 2 participants 4 messages Jan 19, 2010 Documentation

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Mel Gorman

author

2010-01-19 18:00 UTC #0 lore raw

PATCH 1/1 delay-accounting: Re-implement -c for getdelays.c to report information on a target command

Task delay-accounting was identified as one means of determining how long a process spends in congestion_wait() without adding new statistics. For example, if the workload should not be doing IO, delay-accounting could reveal how long it was spending in unexpected IO or delays. Unfortunately, on closer examination it was clear that getdelays does not act as documented.

Commit a3baf649 added Documentation/accounting/getdelays.c with a -c switch that was documented to fork/exec a child and report statistics on it but for reasons that are unclear to me, commit 9e06d3f9 deleted support for this switch but did not update the documentation. It might be an oversight or it might be because the control flow of the program meant that accounting information would be printed once early in the lifetime of the program making it of limited use.

This patch reimplements -c for getdelays.c to act as documented. Unlike the original version, it waits until the command completes before printing any information on it. An example of it being used looks like

$ ./getdelays -d -c find /home/mel -name mel
print delayacct stats ON
/home/mel
/home/mel/.notes-wine/drive_c/windows/profiles/mel
/home/mel/.wine/drive_c/windows/profiles/mel
/home/mel/git-configs/dot.kde/share/apps/konqueror/home/mel
PID	5923

CPU count real total virtual total delay total

                42779     5051232096     5164722692      564207988
IO              count    delay total
                41727    97804147758
SWAP            count    delay total

0 0
RECLAIM count delay total
0 0

It's not clear how or if this subsystem is being maintained. If the authors agree on it but do not pick it up for merging, I'll go bug Andrew with it.

Signed-off-by Mel Gorman <[email protected]>

---

 Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

Documentation/accounting/getdelays.c +35 -2

index 6e25c26..c6648bc 100644
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include <signal.h>
 
 #include <linux/genetlink.h>

@@ -266,11 +267,13 @@ int main(int argc, char *argv[])
 	int containerset = 0;
 	char containerpath[1024];
 	int cfd = 0;
+	int forking = 0;
+	sigset_t sigset;
 
 	struct msgtemplate msg;
 
-	while (1) {
-		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:");
+	while (!forking) {
+		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:c:");
 		if (c < 0)
 			break;

@@ -319,6 +322,27 @@ int main(int argc, char *argv[])
 				err(1, "Invalid pid\n");
 			cmd_type = TASKSTATS_CMD_ATTR_PID;
 			break;
+		case 'c':
+
+			/* Block SIGCHLD for sigwait() later */
+			if (sigemptyset(&sigset) == -1)
+				err(1, "Failed to empty sigset");
+			if (sigaddset(&sigset, SIGCHLD))
+				err(1, "Failed to set sigchld in sigset");
+			sigprocmask(SIG_BLOCK, &sigset, NULL);
+
+			/* fork/exec a child */
+			tid = fork();
+			if (tid < 0)
+				err(1, "Fork failed\n");
+			if (tid == 0)
+				if (execvp(argv[optind - 1], &argv[optind - 1]) < 0)
+					exit(-1);
+
+			/* Set the command type and avoid further processing */
+			cmd_type = TASKSTATS_CMD_ATTR_PID;
+			forking = 1;
+			break;
 		case 'v':
 			printf("debug on\n");
 			dbg = 1;

@@ -370,6 +394,15 @@ int main(int argc, char *argv[])
 		goto err;
 	}
 
+	/*
+	 * If we forked a child, wait for it to exit. Cannot use waitpid()
+	 * as all the delicious data would be reaped as part of the wait 
+	 */
+	if (tid && forking) {
+		int sig_received;
+		sigwait(&sigset, &sig_received);
+	}
+
 	if (tid) {
 		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,
 			      cmd_type, &tid, sizeof(__u32));

Balbir Singh

2010-01-19 18:13 UTC #1 lore raw

Quoted 9 lines · Mel Gorman

Task delay-accounting was identified as one means of determining how long a process spends in congestion_wait() without adding new statistics. For example, if the workload should not be doing IO, delay-accounting could reveal how long it was spending in unexpected IO or delays. Unfortunately, on closer examination it was clear that getdelays does not act as documented.
Commit a3baf649 added Documentation/accounting/getdelays.c with a -c switch that was documented to fork/exec a child and report statistics on it but for reasons that are unclear to me, commit 9e06d3f9 deleted support for this

That is an oversight and not intentional. I've not gotten around to reimplementing the -c option due to lack for people asking for it.

Quoted 9 lines

switch but did not update the documentation. It might be an oversight or it might be because the control flow of the program meant that accounting information would be printed once early in the lifetime of the program making it of limited use.
This patch reimplements -c for getdelays.c to act as documented. Unlike the original version, it waits until the command completes before printing any information on it. An example of it being used looks like

Looks good, could you please keep the original sign-offs as well?

Quoted 13 lines

$ ./getdelays -d -c find /home/mel -name mel
print delayacct stats ON
/home/mel
/home/mel/.notes-wine/drive_c/windows/profiles/mel
/home/mel/.wine/drive_c/windows/profiles/mel
/home/mel/git-configs/dot.kde/share/apps/konqueror/home/mel
PID	5923

CPU count real total virtual total delay total

                42779     5051232096     5164722692      564207988
IO              count    delay total
                41727    97804147758
SWAP            count    delay total

Quoted 8 lines

0 0
RECLAIM count delay total
0 0
It's not clear how or if this subsystem is being maintained. If the authors agree on it but do not pick it up for merging, I'll go bug Andrew with it.

I am maintaining it, please do let me know if you have an issue with the subsystem or utilities.

Quoted 77 lines

Signed-off-by Mel Gorman <[email protected]>

---

 Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

Documentation/accounting/getdelays.c +35 -2

index 6e25c26..c6648bc 100644
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include <signal.h>
 
 #include <linux/genetlink.h>

@@ -266,11 +267,13 @@ int main(int argc, char *argv[])
 	int containerset = 0;
 	char containerpath[1024];
 	int cfd = 0;
+	int forking = 0;
+	sigset_t sigset;
 
 	struct msgtemplate msg;
 
-	while (1) {
-		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:");
+	while (!forking) {
+		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:c:");
 		if (c < 0)
 			break;

@@ -319,6 +322,27 @@ int main(int argc, char *argv[])
 				err(1, "Invalid pid\n");
 			cmd_type = TASKSTATS_CMD_ATTR_PID;
 			break;
+		case 'c':
+
+			/* Block SIGCHLD for sigwait() later */
+			if (sigemptyset(&sigset) == -1)
+				err(1, "Failed to empty sigset");
+			if (sigaddset(&sigset, SIGCHLD))
+				err(1, "Failed to set sigchld in sigset");
+			sigprocmask(SIG_BLOCK, &sigset, NULL);
+
+			/* fork/exec a child */
+			tid = fork();
+			if (tid < 0)
+				err(1, "Fork failed\n");
+			if (tid == 0)
+				if (execvp(argv[optind - 1], &argv[optind - 1]) < 0)
+					exit(-1);
+
+			/* Set the command type and avoid further processing */
+			cmd_type = TASKSTATS_CMD_ATTR_PID;
+			forking = 1;
+			break;
 		case 'v':
 			printf("debug on\n");
 			dbg = 1;

@@ -370,6 +394,15 @@ int main(int argc, char *argv[])
 		goto err;
 	}
 
+	/*
+	 * If we forked a child, wait for it to exit. Cannot use waitpid()
+	 * as all the delicious data would be reaped as part of the wait 
+	 */
+	if (tid && forking) {
+		int sig_received;
+		sigwait(&sigset, &sig_received);
+	}
+
 	if (tid) {
 		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,
 			      cmd_type, &tid, sizeof(__u32));

Mel Gorman

author

2010-01-19 18:52 UTC #2 lore raw

Quoted 7 lines · Balbir Singh

Quoted 6 lines · Mel Gorman
Task delay-accounting was identified as one means of determining how long a process spends in congestion_wait() without adding new statistics. For example, if the workload should not be doing IO, delay-accounting could reveal how long it was spending in unexpected IO or delays. Unfortunately, on closer examination it was clear that getdelays does not act as documented.

Quoted 7 lines

Quoted 3 lines
Commit a3baf649 added Documentation/accounting/getdelays.c with a -c switch that was documented to fork/exec a child and report statistics on it but for reasons that are unclear to me, commit 9e06d3f9 deleted support for this
That is an oversight and not intentional. I've not gotten around to reimplementing the -c option due to lack for people asking for it.

Consider this a request then. Man, I'd really like if someone implemented that -c switch thing :P

Quoted 5 lines

Quoted 5 lines
switch but did not update the documentation. It might be an oversight or it might be because the control flow of the program meant that accounting information would be printed once early in the lifetime of the program making it of limited use.

Quoted 7 lines

Quoted 4 lines
This patch reimplements -c for getdelays.c to act as documented. Unlike the original version, it waits until the command completes before printing any information on it. An example of it being used looks like
Looks good, could you please keep the original sign-offs as well?

Well, the reimplementation is significantly different to what was there so I'm not sure that's appropriate. Look at the differences yourself.

Quoted 17 lines

$ ./getdelays -d -c find /home/mel -name mel
print delayacct stats ON
/home/mel
/home/mel/.notes-wine/drive_c/windows/profiles/mel
/home/mel/.wine/drive_c/windows/profiles/mel
/home/mel/git-configs/dot.kde/share/apps/konqueror/home/mel
PID	5923

CPU count real total virtual total delay total

                42779     5051232096     5164722692      564207988
IO              count    delay total
                41727    97804147758
SWAP            count    delay total

0 0
RECLAIM count delay total
0 0

Quoted 8 lines

Quoted 4 lines
It's not clear how or if this subsystem is being maintained. If the authors agree on it but do not pick it up for merging, I'll go bug Andrew with it.
I am maintaining it, please do let me know if you have an issue with the subsystem or utilities.

If you're happy with the patch then, can you pick it up, add your signed-off-by and go with whatever submission path you use for this subsystem?

Thanks

Quoted 78 lines

Quoted 77 lines

Signed-off-by Mel Gorman <[email protected]>

---

 Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

Documentation/accounting/getdelays.c +35 -2

index 6e25c26..c6648bc 100644
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include <signal.h>
 
 #include <linux/genetlink.h>

@@ -266,11 +267,13 @@ int main(int argc, char *argv[])
 	int containerset = 0;
 	char containerpath[1024];
 	int cfd = 0;
+	int forking = 0;
+	sigset_t sigset;
 
 	struct msgtemplate msg;
 
-	while (1) {
-		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:");
+	while (!forking) {
+		c = getopt(argc, argv, "qdiw:r:m:t:p:vlC:c:");
 		if (c < 0)
 			break;

@@ -319,6 +322,27 @@ int main(int argc, char *argv[])
 				err(1, "Invalid pid\n");
 			cmd_type = TASKSTATS_CMD_ATTR_PID;
 			break;
+		case 'c':
+
+			/* Block SIGCHLD for sigwait() later */
+			if (sigemptyset(&sigset) == -1)
+				err(1, "Failed to empty sigset");
+			if (sigaddset(&sigset, SIGCHLD))
+				err(1, "Failed to set sigchld in sigset");
+			sigprocmask(SIG_BLOCK, &sigset, NULL);
+
+			/* fork/exec a child */
+			tid = fork();
+			if (tid < 0)
+				err(1, "Fork failed\n");
+			if (tid == 0)
+				if (execvp(argv[optind - 1], &argv[optind - 1]) < 0)
+					exit(-1);
+
+			/* Set the command type and avoid further processing */
+			cmd_type = TASKSTATS_CMD_ATTR_PID;
+			forking = 1;
+			break;
 		case 'v':
 			printf("debug on\n");
 			dbg = 1;

@@ -370,6 +394,15 @@ int main(int argc, char *argv[])
 		goto err;
 	}
 
+	/*
+	 * If we forked a child, wait for it to exit. Cannot use waitpid()
+	 * as all the delicious data would be reaped as part of the wait 
+	 */
+	if (tid && forking) {
+		int sig_received;
+		sigwait(&sigset, &sig_received);
+	}
+
 	if (tid) {
 		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,
 			      cmd_type, &tid, sizeof(__u32));

Signature · 3 lines

Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

Balbir Singh

2010-01-19 19:03 UTC #3 lore raw

Quoted 8 lines · Mel Gorman

Quoted 4 lines
That is an oversight and not intentional. I've not gotten around to reimplementing the -c option due to lack for people asking for it.
Consider this a request then. Man, I'd really like if someone implemented that -c switch thing :P

Quoted 11 lines

Quoted 7 lines
Quoted 4 lines
This patch reimplements -c for getdelays.c to act as documented. Unlike the original version, it waits until the command completes before printing any information on it. An example of it being used looks like
Looks good, could you please keep the original sign-offs as well?
Well, the reimplementation is significantly different to what was there so I'm not sure that's appropriate. Look at the differences yourself.

Fair enough

Quoted 22 lines

Quoted 22 lines
Quoted 21 lines
$ ./getdelays -d -c find /home/mel -name mel
print delayacct stats ON
/home/mel
/home/mel/.notes-wine/drive_c/windows/profiles/mel
/home/mel/.wine/drive_c/windows/profiles/mel
/home/mel/git-configs/dot.kde/share/apps/konqueror/home/mel
PID	5923
CPU count real total virtual total delay total
                42779     5051232096     5164722692      564207988
IO              count    delay total
                41727    97804147758
SWAP            count    delay total
0 0
RECLAIM count delay total
0 0
It's not clear how or if this subsystem is being maintained. If the authors agree on it but do not pick it up for merging, I'll go bug Andrew with it.

Quoted 8 lines

Quoted 3 lines
I am maintaining it, please do let me know if you have an issue with the subsystem or utilities.
If you're happy with the patch then, can you pick it up, add your signed-off-by and go with whatever submission path you use for this subsystem?

Absolutely!

Signed-off-by Balbir Singh <[email protected]>

Andrew, could you please pick this up?

Thanks,
Balbir Singh.