[PATCH] examples: Fix vm_power_manager scratch area to /run/dpdk/powermonitor

[Sudheendra S]

Hi Stephen,

I appreciate any feedback so that I can make changes and send out the patch.

Thanks

On Thu, Jun 18, 2026 at 12:24 PM Sudheendra S <giveback4fun at gmail.com>
wrote:

> *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
>
> On Fri, May 29, 2026 at 9:01 AM Bruce Richardson <
> bruce.richardson at intel.com> wrote:
>
>> On Fri, May 29, 2026 at 08:23:24AM -0700, Stephen Hemminger wrote:
>> > On Fri, 29 May 2026 09:01:34 +0100
>> > Bruce Richardson <bruce.richardson at intel.com> wrote:
>> >
>> > > On Thu, May 28, 2026 at 07:04:48PM +0000, Sudheendra Sampath wrote:
>> > > > 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
>> >
>> > 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;
>> >       }
>>
>> 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
>>
>
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