18 Jan
2015
18 Jan
'15
3:20 a.m.
Noel Chiappa <jnc(a)mercury.lcs.mit.edu> writes:
It all depends on the particular driver; some drivers
(e.g. the RP
driver) re-organized the waiting request queue to optimize head
motion, using a so-called 'elevator algorithm'.
Ah, yes, now that you point it out, I see the sorting in the RP driver.
I really think the whole triple-sync thing is
mythology.
It looks that way, yes. The fact that it does a synchronous write of
the superblocks at the start of the sync seems to imply that two
successive calls should ensure a proper flushing of everything, and may
even have been written like that with that effect in mind, but once disk
drivers started optimizing I/O ordering, the effect was lost - which
might just be why the synchronous superblock write was gone in V7.
-tih
--
Popularity is the hallmark of mediocrity. --Niles Crane, "Frasier"