31 Jan
2021
31 Jan
'21
4:37 a.m.
On Sat, Jan 30, 2021 at 3:32 PM Larry McVoy <lm(a)mcvoy.com> wrote:
On Sun, Jan 31, 2021 at 09:27:10AM +1100, Dave
Horsfall wrote:
the
Yes. There's no actual code in the System V or earlier kernels to block any
of the sync calls. At least none I could find in examining all the 'leaked
sources' I could find on the internet.
sync just schedules I/O. There's nothing in the system call that waits for
anything: it just goes through the list of all non-busy buffers calling the
driver's strategy routine and marking the buffer as busy.
Later systems, like SunOS did have a wait, but that was a later addition,
done a half a dozen different ways. BSD had one that waited for a while,
but gave up after some tens of seconds...
Warner
On Tue, 26 Jan 2021, Greg A. Woods wrote:
>The lore I was told at the time was that you alwasy ran three and that
it
didn't matter if they were all on the same line with semicolons or not
because of the very fact that the second one would block.
What I was taught was:
% sync
% sync
% sync
and never:
% sync; sync; sync
The theory was that by waiting for the shell prompt each time, it gave buffer pool enough time to be flushed.
I was taught the exact same thing and for the same reasons.