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From: "Liang, Cunming" <cunming.liang@intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>
Thread-Topic: [dpdk-dev] [PATCH v4 07/17] eal: add rte_gettid() to acquire
unique system tid
Thread-Index: AQHQPoxlK7byiujpnkC07bixNU4v85zmsJOAgALNhvA=
Date: Tue, 10 Feb 2015 06:57:23 +0000
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Subject: Re: [dpdk-dev] [PATCH v4 07/17] eal: add rte_gettid() to acquire
unique system tid
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> -----Original Message-----
> From: Olivier MATZ [mailto:olivier.matz@6wind.com]
> Sent: Monday, February 09, 2015 4:01 AM
> To: Liang, Cunming; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v4 07/17] eal: add rte_gettid() to acquire=
unique
> system tid
>=20
> Hi,
>=20
> On 02/02/2015 03:02 AM, Cunming Liang wrote:
> > The rte_gettid() wraps the linux and freebsd syscall gettid().
> > It provides a persistent unique thread id for the calling thread.
> > It will save the unique id in TLS on the first time.
> >
> > [...]
> >
> > +/**
> > + * A wrap API for syscall gettid.
> > + *
> > + * @return
> > + * On success, returns the thread ID of calling process.
> > + * It always successful.
> > + */
> > +int rte_sys_gettid(void);
> > +
> > +/**
> > + * Get system unique thread id.
> > + *
> > + * @return
> > + * On success, returns the thread ID of calling process.
> > + * It always successful.
> > + */
> > +static inline int rte_gettid(void)
> > +{
> > + static RTE_DEFINE_PER_LCORE(int, _thread_id) =3D -1;
> > + if (RTE_PER_LCORE(_thread_id) =3D=3D -1)
> > + RTE_PER_LCORE(_thread_id) =3D rte_sys_gettid();
> > + return RTE_PER_LCORE(_thread_id);
> > +}
>=20
> Instead of doing the test each time rte_gettid() is called, why not
> having 2 functions:
> rte_init_tid() -> assign the per_lcore variable
> rte_gettid() -> return the per_lcore variable
[LCM] The rte_gettid() mainly used in recursive spinlock.
For non-EAL thread, we don't expect new user thread has to explicit call so=
mething.
The purpose to call it in EAL thread init, is to lower down the overhead of=
the first calling for EAL thread.
>=20
>=20
>=20
> Regards,
> Olivier