svn commit: r312694 - in head: sys/cam/ctl usr.sbin/ctladm

[Alexander Motin]

On 24.01.2017 15:14, Konstantin Belousov wrote:
> On Tue, Jan 24, 2017 at 12:13:41PM +0000, Alexander Motin wrote:
>> Author: mav
>> Date: Tue Jan 24 12:13:41 2017
>> New Revision: 312694
>> URL: https://svnweb.freebsd.org/changeset/base/312694
>>
>> Log:
>>   Make CTL ramdisk backend a real RAM disk.
>>   
>>   If "capacity" LU option is set, ramdisk backend now implements featured
>>   thin provisioned disk, storing data in malloc(9) allocated memory blocks
>>   of pblocksize bytes (default PAGE_SIZE or 4KB).  Additionally ~0.2% of LU
>>   size is used for indirection tree (bigger pblocksize reduce the overhead).
>>   Backend supports all unmap and anchor operations.  If configured capacity
>>   is overflowed, proper error conditions are reported.
>>   
>>   If "capacity" LU option is not set, the backend operates mostly the same
>>   as before without allocating real storage: writes go to nowhere, reads
>>   return zeroes, reporting that all LBAs are unmapped.
>>   
>>   This backend is still mostly oriented on testing and benchmarking (it is
>>   still a volatile RAM disk), but now it should allow to run real FS tests,
>>   not only simple dumb dd.
> 
> This sounds too much like malloc-backed md(4).

Yes, it is.  Just without memory copies and GEOM calls, and with some
additional SCSI features.

-- 
Alexander Motin