* Re: Finegrained a/c/mtime was Re: Directory notification pr
@ 2001-10-05 15:27 Petr Vandrovec
2001-10-05 13:41 ` Jonathan Lundell
0 siblings, 1 reply; 2+ messages in thread
From: Petr Vandrovec @ 2001-10-05 15:27 UTC (permalink / raw)
To: Padraig Brady; +Cc: Alex Larsson, Ulrich Drepper, linux-kernel
On 5 Oct 01 at 14:15, Padraig Brady wrote:
> >Another advantage of using the real time instead of a counter is that
> >you can easily merge the both values into a single 64bit value and do
> >arithmetic on it in user space. With a generation counter you would need
> >to work with number pairs, which is much more complex.
> >
> ??
> if (file->mtime != mtime || file->gen_count != gen_count)
> file_changed=1;
make needs comparing timestamps between two files. I cannot imagine
how you can get this working (without network filesystem you can
have global gen_count, but with network filesystem each server has
its own gen_count... and using world-wide nanoseconds instead of world-wide
gen_count looks much simpler to me ;-) )
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: Finegrained a/c/mtime was Re: Directory notification pr
2001-10-05 15:27 Finegrained a/c/mtime was Re: Directory notification pr Petr Vandrovec
@ 2001-10-05 13:41 ` Jonathan Lundell
0 siblings, 0 replies; 2+ messages in thread
From: Jonathan Lundell @ 2001-10-05 13:41 UTC (permalink / raw)
To: Petr Vandrovec; +Cc: linux-kernel
At 3:27 PM -0700 2001-10-05, Petr Vandrovec wrote:
>On 5 Oct 01 at 14:15, Padraig Brady wrote:
>> >Another advantage of using the real time instead of a counter is that
>> >you can easily merge the both values into a single 64bit value and do
>> >arithmetic on it in user space. With a generation counter you would need
>> >to work with number pairs, which is much more complex.
>> >
>> ??
>> if (file->mtime != mtime || file->gen_count != gen_count)
>> file_changed=1;
>
>make needs comparing timestamps between two files. I cannot imagine
>how you can get this working (without network filesystem you can
>have global gen_count, but with network filesystem each server has
>its own gen_count... and using world-wide nanoseconds instead of world-wide
>gen_count looks much simpler to me ;-) )
Except for the world-wide-nanosecond-resolution synchronization problem....
Even keeping cycle-counter-based systems in sync within SMP systems
seems problematical, depending on how the counters are implemented.
--
/Jonathan Lundell.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2001-10-05 15:27 Finegrained a/c/mtime was Re: Directory notification pr Petr Vandrovec
2001-10-05 13:41 ` Jonathan Lundell
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