> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Stephen > Hemminger > Sent: Monday, December 22, 2014 7:29 PM > To: Richardson, Bruce > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [RFC PATCH 0/7] support multi-phtread per lcore > > On Mon, 22 Dec 2014 09:46:03 +0000 > Bruce Richardson <bruce.richardson at intel.com> wrote: > > > On Mon, Dec 22, 2014 at 01:51:27AM +0000, Liang, Cunming wrote: > > > ... > > > > I'm conflicted on this one. However, I think far more applications would > be > > > > broken > > > > to start having to use thread_id in place of an lcore_id than would be > broken > > > > by having the lcore_id no longer actually correspond to a core. > > > > I'm actually struggling to come up with a large number of scenarios > where it's > > > > important to an app to determine the cpu it's running on, compared to > the large > > > > number of cases where you need to have a data-structure per thread. > In DPDK > > > > libs > > > > alone, you see this assumption that lcore_id == thread_id a large > number of > > > > times. > > > > > > > > Despite the slight logical inconsistency, I think it's better to avoid > introducing > > > > a thread-id and continue having lcore_id representing a unique thread. > > > > > > > > /Bruce > > > > > > Ok, I understand it. > > > I list the implicit meaning if using lcore_id representing the unique > > > thread. > > > 1). When lcore_id less than RTE_MAX_LCORE, it still represents the logical > core id. > > > 2). When lcore_id large equal than RTE_MAX_LCORE, it represents an > unique id for thread. > > > 3). Most of APIs(except rte_lcore_id()) in rte_lcore.h suggest to be used > only in CASE 1) > > > 4). rte_lcore_id() can be used in CASE 2), but the return value no matter > represent a logical core id. > > > > > > If most of us feel it's acceptable, I'll prepare for the RFC v2 base on > > > this > conclusion. > > > > > > /Cunming > > > > Sorry, I don't like that suggestion either, as having lcore_id values > > greater > > than RTE_MAX_LCORE is terrible, as how will people know how to > dimension arrays > > to be indexes by lcore id? Given the choice, if we are not going to just use > > lcore_id as a generic thread id, which is always between 0 and > RTE_MAX_LCORE > > we can look to define a new thread_id variable to hold that. However, it > should > > have a bounded range. > > From an ease-of-porting perspective, I still think that the simplest option > > is > to > > use the existing lcore_id and accept the fact that it's now a thread id > > rather > > than an actual physical lcore. Question is, is would that cause us lots of > issues > > in the future? > > > > /Bruce > > The current rte_lcore_id() has different meaning the thread. Your proposal > will > break code that uses lcore_id to do per-cpu statistics and the lcore_config > code in the samples. > q It depends on application context and how application treats rte_lcore_id() core. When number of the threads will not exceed the number of cores (let's say old-fashioned DPDK application) all stuff like per-cpu statistics will work correctly.
When we treat threads on cores as ordinary threads as we introducing the special function rte_pthread_create() - the meaning of rte_lcore_id() changes to indicate thread number what is correct under new assumptions and new application model. I do not want to limit DPDK design to only per-cpu application. There is much more application models that could be supported using DPDK. Current per-cpu approach is only a subset of the possible applications. Maybe we should indicate something like CONFIG_RTE_PTHREAD_ENABLE to change a meaning of rte_lcore_id() and introducing rte_pthread_create() family. Mirek