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

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

[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
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 <mel@csn.ul.ie>
--- 
 Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
index 6e25c26..c6648bc 100644
--- a/Documentation/accounting/getdelays.c
+++ b/Documentation/accounting/getdelays.c
@@ -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));

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

[Balbir Singh]

On Tuesday 19 January 2010 11:30 PM, Mel Gorman wrote:
> 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.

> 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?

> $ ./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.
> 

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

> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> --- 
>  Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
>  1 file changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
> index 6e25c26..c6648bc 100644
> --- a/Documentation/accounting/getdelays.c
> +++ b/Documentation/accounting/getdelays.c
> @@ -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));

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

[Mel Gorman]

On Tue, Jan 19, 2010 at 11:43:43PM +0530, Balbir Singh wrote:
> On Tuesday 19 January 2010 11:30 PM, Mel Gorman wrote:
> > 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.
> 

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

> > 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?
> 

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

> > $ ./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.
> > 
> 
> 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

> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> > --- 
> >  Documentation/accounting/getdelays.c |   37 +++++++++++++++++++++++++++++++++--
> >  1 file changed, 35 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
> > index 6e25c26..c6648bc 100644
> > --- a/Documentation/accounting/getdelays.c
> > +++ b/Documentation/accounting/getdelays.c
> > @@ -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
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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

[Balbir Singh]

On Wednesday 20 January 2010 12:22 AM, Mel Gorman wrote:
>>
>> 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
> 

:)

>>> 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

>>> $ ./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.
>>>
>>
>> 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 <balbir@linux.vnet.ibm.com>

Andrew, could you please pick this up?

Thanks,
Balbir Singh.