On Wed, Mar 04, 2015 at 06:28:05AM -0500, Neil Horman wrote: > On Wed, Mar 04, 2015 at 01:05:07PM +0200, Panu Matilainen wrote: > > On 03/04/2015 11:24 AM, Thomas Monjalon wrote: > > >Hi Panu, > > > > > >2015-03-04 08:17, Panu Matilainen: > > >>With symbol versioning its vital that developers test their code in > > >>shared library mode, otherwise we'll be playing "add the forgotten > > >>symbol export" from here to eternity. > > > > > >Yes we must improve the sanity checks. > > >A lot of options must be tested (or removed) and not only shared libs. > > >But the error you reported before (missing export of > > >rte_eth_dev_release_port) > > >cannot be seen even with this patch. > > > > I know, I didn't say it would have directly caught it. It would've likely > > been found earlier though, if nothing else then in testing of the new > > librte_pmd_null which clearly nobody had tried in shared lib configuration. > > > This is accurate. The default config is a tool, in the sense that it > leverages > the implicit testing of any users who are experimenting with the DPDK. Any > users out there using the DPDK test/example applications would have realized > something was amiss when the testpmd app refused to run with the null or pcap > pmd, since there was a missing symbol. That "social fuzzing" has value, but > it > only works if the defaults are carefully selected. Currently, building for > shared libraries exposes more existing bugs than static libraries, and so we > should set that as our default so as to catch them. > > > >It means we need more tools. > > >Though, default configuration is not a tool. > > > > Yes, default config is not a tool, its a recommendation of sorts both for > > developers and users. It also tends to be the setup that is rarely broken > > because it happens to get the most testing :) > > > And it is a tool (see above). > > > > > > >>By defaulting to shared we should catch more of these cases early, > > >>but without taking away anybodys ability to build static. > > > > > >Shared libraries are convenient for distributions but have a performance > > >impact. I think that static build must remain the default choice. > > > > If utmost performance is the concern, isn't it reasonable to assume that users > in that demographic will customize their configuration to achieve that? No > one > assumes that something is tuned to be perfect for their needs out of the box > if > their needs are extreemely biased to a single quality. The best course of > action here is to set the default to be adventageous toward catching bugs, and > document the changes needed to bias for performance. > > > For distros, this is not a matter of *convenience*, its the only technically > > feasible choice.
As I understand it, build for the "default" cpu rather than "native" is the only feasible choice also, so how about re-introducing a new defconfig file for "default" (or perhaps better name), where you have lowest-common denominator instruction-set and building for shared libraries? Would that work for everyone, or do people feel it would be too confusing to have more defconfig files available? /Bruce > > > > I didn't want to make the commit message into a shared library sermon, but > > if you look at the OSS landscape overall the common wisdom is that shared > > library benefits outweigh any performance impact by so much that static libs > > are almost nowhere to be found. I can change the text into a full-blown > > rationale why shared libraries should be the default if that makes any > > difference. > > > Embedded applications actually do make extensive use of static linking to try > achieve greater performance, but they tend to be proprietary, and as such are > the exception that proves the rule. Once an application itself becomes open > source, it biases toward shared libraries, because the minor performance > impact > is well worth the increased manageability and security found in DSO's > > Acked-by: Neil Horman <nhorman at tuxdriver.com> > > > - Panu - > > > >
