[ovs-dev] [PATCH] dpif-netdev: Add core id in the PMD thread name.

[David Marchand]

On Wed, Aug 14, 2019 at 9:45 AM Ilya Maximets <i.maximets at samsung.com> wrote:
>
> On 13.08.2019 19:46, Eelco Chaudron wrote:
> >
> >
> > On 13 Aug 2019, at 18:37, Ilya Maximets wrote:
> >
> >> This is highly useful to see on which core PMD is running by
> >> only looking at the thread name. Thread Id still allows to
> >> distinguish different threads running on the same core over the time:
> >>
> >>    |dpif_netdev(pmd-c10/id:53)|DBG|Creating 2. subtable <...>
> >>    |dpif_netdev(pmd-c10/id:53)|DBG|flow_add: <...>, actions:2
> >>    |dpif_netdev(pmd-c09/id:70)|DBG|Core 9 processing port <..>
> >>
> >> In gdb, top or any other utility it's useful to quickly catch up
> >> needed thread without parsing logs, memory or matching threads by port
> >> names they're handling.
> >>
> >> Signed-off-by: Ilya Maximets <i.maximets at samsung.com>
> >> ---
> >>  lib/dpif-netdev.c | 9 ++++++++-
> >>  1 file changed, 8 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> >> index d0a1c58ad..34ba03836 100644
> >> --- a/lib/dpif-netdev.c
> >> +++ b/lib/dpif-netdev.c
> >> @@ -4735,9 +4735,16 @@ reconfigure_pmd_threads(struct dp_netdev *dp)
> >>      FOR_EACH_CORE_ON_DUMP(core, pmd_cores) {
> >>          pmd = dp_netdev_get_pmd(dp, core->core_id);
> >>          if (!pmd) {
> >> +            struct ds name = DS_EMPTY_INITIALIZER;
> >> +
> >>              pmd = xzalloc(sizeof *pmd);
> >>              dp_netdev_configure_pmd(pmd, dp, core->core_id, core->numa_id);
> >> -            pmd->thread = ovs_thread_create("pmd", pmd_thread_main, pmd);
> >> +
> >> +            ds_put_format(&name, "pmd-c%02d/id:", core->core_id);
> >
> > This is a really good idea :) One remark should we make it %03d?
>
> There is a hard limit for the thread name. It's 15 meaningful chars excluding the
> terminating null byte. 'pmd-c02/id:' is 11 bytes wide keeping 4 bytes for the
> thread id. 'pmd-c002/id:' is 12 bytes wide with only 3 bytes remaining for id.
> Thread ids could easily become big ( > 1000) for a long running process, that is
> why %02d was chosen, to save some space.

Do we really need the /id: part?
A c%03d/pmd prefix would keep the existing pmd%d pattern and save 3 characters.

Otherwise, this is a good idea yes.


-- 
David Marchand