examples: Fix vm_power_manager scratch area to /run/dpdk/powermanager

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a directory before creating subdirectory, powermanager.

All directory permissions are 0700.

Signed-off-by Sudheendra Sampath <[email protected]>

---

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a directory before creating subdirectory, powermanager.

Quoted 6 lines · Sudheendra Sampath

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a directory before creating subdirectory, powermanager.

I would suggest using $XDG_RUNTIME_DIR for the directory path, rather than hardcoding it by default. If XDG_RUNTIME_DIR is not set, then maybe consider using /run/dpdk. However, rather than /run/dpdk, I'd suggest using the normal runtime dir path on most distros as the default:
/run/user/<uid>.

/Bruce

Quoted 7 lines · On Fri, 29 May 2026 09:01:34 +0100 Bruce Richardson…

Quoted 6 lines · Sudheendra Sampath

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a directory before creating subdirectory, powermanager.

Quoted 7 lines

I would suggest using $XDG_RUNTIME_DIR for the directory path, rather than hardcoding it by default. If XDG_RUNTIME_DIR is not set, then maybe consider using /run/dpdk. However, rather than /run/dpdk, I'd suggest using the normal runtime dir path on most distros as the default:
/run/user/<uid>.

/Bruce

The login in EAL is a little more detailed.
The choice is from systemd conventions which follows filesystem hierarchy.

int eal_create_runtime_dir(void)

{
	const char *directory;
	char run_dir[PATH_MAX];
	char tmp[PATH_MAX];
	int ret;

	/* from RuntimeDirectory= see systemd.exec */
	directory = getenv("RUNTIME_DIRECTORY");
	if (directory == NULL) {
		/*
		 * Used standard convention defined in
		 * XDG Base Directory Specification and
		 * Filesystem Hierarchy Standard.
		 */
		if (getuid() == 0)
			directory = "/var/run";
		else
			directory = getenv("XDG_RUNTIME_DIR") ? : "/tmp";
	}

	/* create DPDK subdirectory under runtime dir */
	ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
	if (ret < 0 || ret == sizeof(tmp)) {
		EAL_LOG(ERR, "Error creating DPDK runtime path name");
		return -1;
	}

	/* create prefix-specific subdirectory under DPDK runtime dir */
	ret = snprintf(run_dir, sizeof(run_dir), "%s/%s",
			tmp, eal_get_hugefile_prefix());
	if (ret < 0 || ret == sizeof(run_dir)) {
		EAL_LOG(ERR, "Error creating prefix-specific runtime path name");
		return -1;
	}

	/* create the path if it doesn't exist. no "mkdir -p" here, so do it
	 * step by step.
	 */
	ret = mkdir(tmp, 0700);
	if (ret < 0 && errno != EEXIST) {
		EAL_LOG(ERR, "Error creating '%s': %s",
			tmp, strerror(errno));
		return -1;

	}

	ret = mkdir(run_dir, 0700);
	if (ret < 0 && errno != EEXIST) {
		EAL_LOG(ERR, "Error creating '%s': %s",
			run_dir, strerror(errno));
		return -1;
	}

Quoted 8 lines · Stephen Hemminger

Quoted 5 lines · On Fri, 29 May 2026 09:01:34 +0100 Bruce Richardson…

Quoted 4 lines · Sudheendra Sampath

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a

directory

Quoted 3 lines

Quoted 3 lines

Quoted 2 lines

before creating subdirectory, powermanager.

I would suggest using $XDG_RUNTIME_DIR for the directory path, rather

than

Quoted 2 lines

Quoted 2 lines

hardcoding it by default. If XDG_RUNTIME_DIR is not set, then maybe consider using /run/dpdk. However, rather than /run/dpdk, I'd suggest

using

Quoted 7 lines

Quoted 4 lines

the normal runtime dir path on most distros as the default:
/run/user/<uid>.

/Bruce

The login in EAL is a little more detailed.
The choice is from systemd conventions which follows filesystem

hierarchy.

Quoted 27 lines

int eal_create_runtime_dir(void)

{
      const char *directory;
      char run_dir[PATH_MAX];
      char tmp[PATH_MAX];
      int ret;

      /* from RuntimeDirectory= see systemd.exec */
      directory = getenv("RUNTIME_DIRECTORY");
      if (directory == NULL) {
              /*
               * Used standard convention defined in
               * XDG Base Directory Specification and
               * Filesystem Hierarchy Standard.
               */
              if (getuid() == 0)
                      directory = "/var/run";
              else
                      directory = getenv("XDG_RUNTIME_DIR") ? : "/tmp";
      }

      /* create DPDK subdirectory under runtime dir */
      ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
      if (ret < 0 || ret == sizeof(tmp)) {
              EAL_LOG(ERR, "Error creating DPDK runtime path name");

Quoted 8 lines

              return -1;
      }

      /* create prefix-specific subdirectory under DPDK runtime dir */
      ret = snprintf(run_dir, sizeof(run_dir), "%s/%s",
                      tmp, eal_get_hugefile_prefix());
      if (ret < 0 || ret == sizeof(run_dir)) {
              EAL_LOG(ERR, "Error creating prefix-specific runtime path

name");

Quoted 4 lines

              return -1;
      }

      /* create the path if it doesn't exist. no "mkdir -p" here, so do

it

Quoted 7 lines

       * step by step.
       */
      ret = mkdir(tmp, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      tmp, strerror(errno));
              return -1;

Quoted 8 lines

      }

      ret = mkdir(run_dir, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      run_dir, strerror(errno));
              return -1;
      }

Yes. Can the power manager call the rte_eal_get_runtime_dir() API and use that as a basis for its working directory? Save duplicating all this logic.

/Bruce

*Note: Changed subject line from /run/dpdk/powermanager -> /run/dpdk/powermonitor*

Hi All,

Apologies for the delay.

So, I am following the above thread and below are what I understand are the changes that are needed :

1. I see that rte_eal_get_runtime_dir() is RTE_EXPORTED_SYMBOL. I will verify that channel_manager has access to this symbol.
2. Upon successful creation of /run/dpdk, I can mkdir CHANNEL_MGR_SOCKET_PATH (/var/run/dpdk/powermonitor) and opendir() that for subsequent processing.
3. Fixup the documentation to reflect correct powermonitor path

Please let me know if I am missing anything or if I misinterpreting any part of the email exchange.

Thanks for all your help and support.

-Sudheendra G Sampath

Quoted 88 lines · Bruce Richardson

Quoted 8 lines · Stephen Hemminger

Quoted 5 lines · On Fri, 29 May 2026 09:01:34 +0100 Bruce Richardson…

Quoted 4 lines · Sudheendra Sampath

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a

directory

Quoted 3 lines

Quoted 3 lines

Quoted 2 lines

before creating subdirectory, powermanager.

I would suggest using $XDG_RUNTIME_DIR for the directory path, rather

than

Quoted 2 lines

Quoted 2 lines

hardcoding it by default. If XDG_RUNTIME_DIR is not set, then maybe consider using /run/dpdk. However, rather than /run/dpdk, I'd suggest

using

Quoted 7 lines

Quoted 4 lines

the normal runtime dir path on most distros as the default:
/run/user/<uid>.

/Bruce

The login in EAL is a little more detailed.
The choice is from systemd conventions which follows filesystem

hierarchy.

Quoted 27 lines

int eal_create_runtime_dir(void)

{
      const char *directory;
      char run_dir[PATH_MAX];
      char tmp[PATH_MAX];
      int ret;

      /* from RuntimeDirectory= see systemd.exec */
      directory = getenv("RUNTIME_DIRECTORY");
      if (directory == NULL) {
              /*
               * Used standard convention defined in
               * XDG Base Directory Specification and
               * Filesystem Hierarchy Standard.
               */
              if (getuid() == 0)
                      directory = "/var/run";
              else
                      directory = getenv("XDG_RUNTIME_DIR") ? : "/tmp";
      }

      /* create DPDK subdirectory under runtime dir */
      ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
      if (ret < 0 || ret == sizeof(tmp)) {
              EAL_LOG(ERR, "Error creating DPDK runtime path name");

Quoted 8 lines

              return -1;
      }

      /* create prefix-specific subdirectory under DPDK runtime dir */
      ret = snprintf(run_dir, sizeof(run_dir), "%s/%s",
                      tmp, eal_get_hugefile_prefix());
      if (ret < 0 || ret == sizeof(run_dir)) {
              EAL_LOG(ERR, "Error creating prefix-specific runtime path

name");

Quoted 4 lines

              return -1;
      }

      /* create the path if it doesn't exist. no "mkdir -p" here, so do

it

Quoted 7 lines

       * step by step.
       */
      ret = mkdir(tmp, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      tmp, strerror(errno));
              return -1;

Quoted 8 lines

      }

      ret = mkdir(run_dir, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      run_dir, strerror(errno));
              return -1;
      }

Yes. Can the power manager call the rte_eal_get_runtime_dir() API and use that as a basis for its working directory? Save duplicating all this logic.

/Bruce

Quoted 8 lines · Stephen Hemminger

Quoted 5 lines · On Fri, 29 May 2026 09:01:34 +0100 Bruce Richardson…

Quoted 4 lines · Sudheendra Sampath

This patch for bug 1832 will do the following:
1. If /run/dpdk is not present, it will create it first with and then create powermanager directory underneath it.
2. If /run/dpdk is present, it will verify it is actually a

directory

Quoted 3 lines

Quoted 3 lines

Quoted 2 lines

before creating subdirectory, powermanager.

I would suggest using $XDG_RUNTIME_DIR for the directory path, rather

than

Quoted 2 lines

Quoted 2 lines

hardcoding it by default. If XDG_RUNTIME_DIR is not set, then maybe consider using /run/dpdk. However, rather than /run/dpdk, I'd suggest

using

Quoted 7 lines

Quoted 4 lines

the normal runtime dir path on most distros as the default:
/run/user/<uid>.

/Bruce

The login in EAL is a little more detailed.
The choice is from systemd conventions which follows filesystem

hierarchy.

Quoted 27 lines

int eal_create_runtime_dir(void)

{
      const char *directory;
      char run_dir[PATH_MAX];
      char tmp[PATH_MAX];
      int ret;

      /* from RuntimeDirectory= see systemd.exec */
      directory = getenv("RUNTIME_DIRECTORY");
      if (directory == NULL) {
              /*
               * Used standard convention defined in
               * XDG Base Directory Specification and
               * Filesystem Hierarchy Standard.
               */
              if (getuid() == 0)
                      directory = "/var/run";
              else
                      directory = getenv("XDG_RUNTIME_DIR") ? : "/tmp";
      }

      /* create DPDK subdirectory under runtime dir */
      ret = snprintf(tmp, sizeof(tmp), "%s/dpdk", directory);
      if (ret < 0 || ret == sizeof(tmp)) {
              EAL_LOG(ERR, "Error creating DPDK runtime path name");

Quoted 8 lines

              return -1;
      }

      /* create prefix-specific subdirectory under DPDK runtime dir */
      ret = snprintf(run_dir, sizeof(run_dir), "%s/%s",
                      tmp, eal_get_hugefile_prefix());
      if (ret < 0 || ret == sizeof(run_dir)) {
              EAL_LOG(ERR, "Error creating prefix-specific runtime path

name");

Quoted 4 lines

              return -1;
      }

      /* create the path if it doesn't exist. no "mkdir -p" here, so do

it

Quoted 7 lines

       * step by step.
       */
      ret = mkdir(tmp, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      tmp, strerror(errno));
              return -1;

Quoted 8 lines

      }

      ret = mkdir(run_dir, 0700);
      if (ret < 0 && errno != EEXIST) {
              EAL_LOG(ERR, "Error creating '%s': %s",
                      run_dir, strerror(errno));
              return -1;
      }

Yes. Can the power manager call the rte_eal_get_runtime_dir() API and use that as a basis for its working directory? Save duplicating all this logic.

/Bruce