From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: Neil Horman <nhorman@tuxdriver.com>, dev@dpdk.org
Cc: David Marchand <david.marchand@6wind.com>,
Stephen Hemminger <stephen@networkplumber.org>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
Panu Matilainen <pmatilai@redhat.com>
Subject: Re: [dpdk-dev] [RFC PATCH 0/4]: Implement module information export
Date: Wed, 04 May 2016 23:16:42 +0200 [thread overview]
Message-ID: <2684085.G5NnXQEQ33@xps13> (raw)
In-Reply-To: <20160504114305.GA27687@hmsreliant.think-freely.org>
This discussion requires more opinions.
Please everybody, READ and COMMENT. Thanks
If it is not enough visible, a new thread could be started later.
2016-05-04 07:43, Neil Horman:
> On Wed, May 04, 2016 at 10:24:18AM +0200, David Marchand wrote:
> > On Tue, May 3, 2016 at 1:57 PM, Neil Horman <nhorman@tuxdriver.com> wrote:
> > >> This approach has a few pros and cons:
> > >>
> > >> pros:
> > >> 1) Its simple, and doesn't require extra infrastructure to implement. E.g. we
> > >> don't need a new tool to extract driver information and emit the C code to build
> > >> the binary data for the special section, nor do we need a custom linker script
> > >> to link said special section in place
> > >>
> > >> 2) Its stable. Because the marker symbols are explicitly exported, this
> > >> approach is resilient against stripping.
It is a good point. We need something resilient against stripping.
> > >> cons:
> > >> 1) It creates an artifact in that PMD_REGISTER_DRIVER has to be used in one
> > >> compilation unit per DSO. As an example em and igb effectively merge two
> > >> drivers into one DSO, and the uses of PMD_REGISTER_DRIVER occur in two separate
> > >> C files for the same single linked DSO. Because of the use of the __COUNTER__
> > >> macro we get multiple definitions of the same marker symbols.
> > >>
> > >> I would make the argument that the downside of the above artifact isn't that big
> > >> a deal. Traditionally in other projects a unit like a module (or DSO in our
> > >> case) only ever codifies a single driver (e.g. module_init() in the linux kernel
> > >> is only ever used once per built module). If we have code like igb/em that
> > >> shares some core code, we should build the shared code to object files and link
> > >> them twice, once to an em.so pmd and again to an igb.so pmd.
It is also a problem for compilation units having PF and VF drivers.
> > >> But regardless, I thought I would propose this to see what you all thought of
> > >> it.
Thanks for proposing.
> > - This implementation does not support binaries, so it is not suitable
> > for people who don't want dso, this is partially why I used bfd rather
> > than just dlopen.
>
> If you're statically linking an application, you should know what hardware you
> support already. Its going to be very hard, if not impossible to develop a
> robust solution that works with static binaries (the prior solutions don't work
> consistently with static binaries either). I really think the static solution
> needs to just be built into the application (i.e. the application needs to add a
> command line option to dump out the pci id's that are registered).
No, we need a tool to know what are the supported devices before running
the application (e.g. for binding).
This tool should not behave differently depending of how DPDK was compiled
(static or shared).
[...]
> > - How does it behave if we strip the dsos ?
>
> I described this above, its invariant to stripping, because the symbols for each
> pmd are explicitly exported, so strip doesn't touch the symbols that pmdinfo
> keys off of.
>
[...]
> > - The tool output format is not script friendly from my pov.
>
> Don't think it really needs to be script friendly, it was meant to provide human
> readable output, but script friendly output can be added easily enough if you
> want.
Yes it needs to be script friendly.
It appears that we must agree on a set of requirements first.
Please let's forget the implementation until we have collected enough
feedbacks on the needs.
I suggest these items to start the list:
- query all drivers in static binary or shared library
- stripping resiliency
- human friendly
- script friendly
- show driver name
- list supported device id / name
- list driver options
- show driver version if available
- show dpdk version
- show kernel dependencies (vfio/uio_pci_generic/etc)
- room for extra information?
Please ack or comment items of this list, thanks.
next prev parent reply other threads:[~2016-05-04 21:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 17:39 Neil Horman
2016-04-26 17:39 ` [dpdk-dev] [RFC PATCH 1/4] pmd: Modify PMD_REGISTER_DRIVER to emit a marker symbol Neil Horman
2016-04-26 17:39 ` [dpdk-dev] [RFC PATCH 2/4] pmds: export this_pmd_driver* symbols Neil Horman
2016-04-26 17:39 ` [dpdk-dev] [RFC PATCH 3/4] pmd: Modify drivers to export appropriate information Neil Horman
2016-04-26 17:39 ` [dpdk-dev] [RFC PATCH 4/4] pmdinfo: Add application to extract pmd driver info Neil Horman
2016-05-03 11:57 ` [dpdk-dev] [RFC PATCH 0/4]: Implement module information export Neil Horman
2016-05-04 8:24 ` David Marchand
2016-05-04 11:43 ` Neil Horman
2016-05-04 21:16 ` Thomas Monjalon [this message]
2016-05-05 9:42 ` Bruce Richardson
2016-05-05 11:38 ` Neil Horman
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