On Wed, 30 Aug 2017 08:05:57 +0200, Greg KH rote:
> On Tue, Aug 29, 2017 at 04:22:34PM +0000, Grant Edwards wrote:
>> Roughly how much kernel memory is allocated for a UART by
>> uart_register_driver() for UARTS that never get instantiated by
>> uart_add_one_port()?
>>
>> A few KB, tens of KB, hundreds of KB?
>> [...]
>
> Should be a pretty easy thing for you to test yourself, right? Build
> two different kernels, look at the memory used, and there you go...
How do you "look at the memory used"?
After a few hours googling, the general consensus seemed to be that
there is no practical way to determine the amount of memory allocated
by a particular module. The only suggestion I found was to watch
slabtop while loading and unloading the module -- along with a caveat
that it usually didn't provide useful info.
I found the caveat to be well-founded. If one assume the memory
allocated by the module can be seen by an increase in the total
"active" memory upon 'insmod' and a decrease upon 'rmmod', then the
memory allocated by the driver is somewhere in the range of -20KB to
+150KB. And there was no observable difference between allocating
space for 32 ports vs. allocating space for 256 ports.
--
Grant Edwards grant.b.edwards Yow! I think I am an
at overnight sensation right
gmail.com now!!
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
