svn commit: r345491 - in head/sys: conf fs/tmpfs modules/tmpfs

[Eugene Grosbein]

25.03.2019 21:12, Ian Lepore wrote:

> On Mon, 2019-03-25 at 05:42 -0700, Cy Schubert wrote:
>> In message <201903250746.x2P7kKUu019786 at repo.freebsd.org>, Allan
>> Jude 
>> writes:
>>> Author: allanjude
>>> Date: Mon Mar 25 07:46:20 2019
>>> New Revision: 345491
>>> URL: https://svnweb.freebsd.org/changeset/base/345491
>>>
>>> Log:
>>>   Make TMPFS_PAGES_MINRESERVED a kernel option
>>>   
>>>   TMPFS_PAGES_MINRESERVED controls how much memory is reserved for
>>> the system
>>>   and not used by tmpfs.
>>>   
>>>   On very small memory systems, the default value may be too high
>>> and this
>>>   prevents these small memory systems from using reroot, which is
>>> required
>>>   for them to install firmware updates.
>>>   
>>>   Submitted by:	Hiroki Mori <yamori813 at yahoo.co.jp>
>>>   Reviewed by:	mizhka
>>>   Differential Revision:	https://reviews.freebsd.org/D13583
>>>
>>> Modified:
>>>   head/sys/conf/options
>>>   head/sys/fs/tmpfs/tmpfs.h
>>>   head/sys/fs/tmpfs/tmpfs_vfsops.c
>>>   head/sys/modules/tmpfs/Makefile
>>>
>>
>> Would this be a good candidate for a sysctl or tuneable?
>>
> 
> The small-memory embedded systems most affected by this often don't use
> loader(8) at all, so tunables aren't an option, and sysctl may be too
> late.  No reason it can't be a tunable as well, but it'll probably need
> to remain as a compile-time option too.

Despite of absense of loader(8), such system still can use our device.hints(5)
compiled in-kernel. For example, geom_map(4) is useful for embedded systems
booted with U-Boot and geom_map uses hints extensively.