From: Neil Horman <nhorman@tuxdriver.com>
To: dev@dpdk.org
Cc: David Marchand <david.marchand@6wind.com>,
Stephen Hemminger <stephen@networkplumber.org>,
bruce.richardson@intel.com, Panu Matilainen <pmatilai@redhat.com>,
Thomas Monjalon <thomas.monjalon@6wind.com>
Subject: Re: [dpdk-dev] [RFC PATCH 0/4]: Implement module information export
Date: Tue, 3 May 2016 07:57:14 -0400 [thread overview]
Message-ID: <20160503115714.GA704@hmsreliant.think-freely.org> (raw)
In-Reply-To: <1461692391-30093-1-git-send-email-nhorman@tuxdriver.com>
On Tue, Apr 26, 2016 at 01:39:47PM -0400, Neil Horman wrote:
> Hey-
> So a few days ago we were reviewing Davids patch series to introduce the
> abiilty to dump hardware support from pmd DSO's in a human readable format.
> That effort encountered some problems, most notably the fact that stripping a
> DSO removed the required information that the proposed tool keyed off, as well
> as the need to dead reckon offsets between symbols that may not be constant
> (dependent on architecture).
>
> I was going to start looking into the possibility of creating a modinfo
> section in a simmilar fashion to what kernel modules do in linux or BSD. I
> decided to propose this solution instead though, because the kernel style
> solution requires a significant amount of infrastructure that I think we can
> maybe avoid maintaining, if we accept some minor caviats
>
> To do this We emit a set of well known marker symbols for each DSO that an
> external application can search for (in this case I called them
> this_pmd_driver<n>, where n is a counter macro). These marker symbols are
> n is a counter macro). These marker symbols are exported by PMDs for
> external access. External tools can then access these symbols via the
> dlopen/dlsym api (or via elfutils libraries)
>
> The symbols above alias the rte_driver struct for each PMD, and the external
> application can then interrogate the registered driver information.
>
> I also add a pointer to the pci id table struct for each PMD so that we can
> export hardware support.
>
> 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.
>
> 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.
>
> But regardless, I thought I would propose this to see what you all thought of
> it.
>
> FWIW, heres sample output of the pmdinfo tool from this series probing the
> librte_pmd_ena.so module:
>
> [nhorman@hmsreliant dpdk]$ ./build/app/pmdinfo
> ~/git/dpdk/build/lib/librte_pmd_ena.so
> PMD 0 Information:
> Driver Name: ena_driver
> Driver Type: PCI
> |====================PCI Table========================|
> | VENDOR ID | DEVICE ID | SUBVENDOR ID | SUBDEVICE ID |
> |-----------------------------------------------------|
> | 1d0f| ec20| ffff| ffff|
> | 1d0f| ec21| ffff| ffff|
> |-----------------------------------------------------|
>
>
>
>
Ping, thoughts here?
Neil
next prev parent reply other threads:[~2016-05-03 11:57 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 ` Neil Horman [this message]
2016-05-04 8:24 ` [dpdk-dev] [RFC PATCH 0/4]: Implement module information export David Marchand
2016-05-04 11:43 ` Neil Horman
2016-05-04 21:16 ` Thomas Monjalon
2016-05-05 9:42 ` Bruce Richardson
2016-05-05 11:38 ` Neil Horman
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