Re: About ceph_clock_now()

[Matt Benjamin <mbenjamin@redhat.com>]

inline

----- Original Message -----
> From: "Adam C. Emerson" <aemerson@redhat.com>
> To: "Willem Jan Withagen" <wjw@digiware.nl>
> Cc: "Matt Benjamin" <mbenjamin@redhat.com>, "Erwan Velu" <evelu@redhat.com>, "Ceph Development"
> <ceph-devel@vger.kernel.org>, "Sage Weil" <sweil@redhat.com>
> Sent: Monday, January 25, 2016 3:14:51 PM
> Subject: Re: About ceph_clock_now()
> 
> On 25/01/2016, Willem Jan Withagen wrote:
> > 1)
> > Currently the code in Adam's looks like:
> > #if defined(CLOCK_MONOTONIC_COARSE)
> >         // Linux systems have _COARSE clocks.
> >         clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
> > #elif defined(CLOCK_MONOTONIC_FAST)
> >         // BSD systems have _FAST clocks.
> >         clock_gettime(CLOCK_MONOTONIC_FAST, &ts);
> > #else
> >         // And if we find neither, you may wish to consult your system's
> >         // documentation.
> > #warning Falling back to CLOCK_MONOTONIC, may be slow.
> >         clock_gettime(CLOCK_MONOTONIC, &ts);
> > #endif
> > 
> > And this is repeated in a few more locations.
> > Moreover, it will be required to do that a few times everytime
> > clock_getime is used.
> 
> I was originally thinking of just specifying the time constant, but I figured
> that somehow somewhere someone might want to compile on a system without
> clock_gettime. (Windows? I don't know.) Or use the fasttime library or
> something
> where just switching out the constant wouldn't work.
> 
> I wouldn't worry about people having to do this every tie they call
> clock_gettime, though, since they really ought to be going through the C++
> Clock
> abstraction. (At least, in the context of the Ceph codebase.)

exactly, this.

> 
> --
> Senior Software Engineer           Red Hat Storage, Ann Arbor, MI, US
> IRC: Aemerson@{RedHat, OFTC, Freenode}
> 0x80F7544B90EDBFB9 E707 86BA 0C1B 62CC 152C  7C12 80F7 544B 90ED BFB9
> 

-- 
-- 
Matt Benjamin
Red Hat, Inc.
315 West Huron Street, Suite 140A
Ann Arbor, Michigan 48103

http://www.redhat.com/en/technologies/storage

tel.  734-707-0660
fax.  734-769-8938
cel.  734-216-5309