svn commit: r269134 - head/sys/vm

Alan Cox alc at
Sat Aug 2 05:02:42 UTC 2014

On 07/29/2014 05:38, Slawa Olhovchenkov wrote:
> On Sat, Jul 26, 2014 at 06:10:18PM +0000, Alan Cox wrote:
>> Author: alc
>> Date: Sat Jul 26 18:10:18 2014
>> New Revision: 269134
>> URL:
>> Log:
>>   When unwiring a region of an address space, do not assume that the
>>   underlying physical pages are mapped by the pmap.  If, for example, the
>>   application has performed an mprotect(..., PROT_NONE) on any part of the
>>   wired region, then those pages will no longer be mapped by the pmap.
>>   So, using the pmap to lookup the wired pages in order to unwire them
>>   doesn't always work, and when it doesn't work wired pages are leaked.
>>   To avoid the leak, introduce and use a new function vm_object_unwire()
>>   that locates the wired pages by traversing the object and its backing
>>   objects.
> MFC planed?

At some point, yes.  However, I'm not sure that it will be MFCed in time
for 10.1.

>>   At the same time, switch from using pmap_change_wiring() to the recently
>>   introduced function pmap_unwire() for unwiring the region's mappings.
>>   pmap_unwire() is faster, because it operates a range of virtual addresses
>>   rather than a single virtual page at a time.  Moreover, by operating on
>>   a range, it is superpage friendly.  It doesn't waste time performing
>>   unnecessary demotions.
>>   Reported by:	markj
>>   Reviewed by:	kib
>>   Tested by:	pho, jmg (arm)
>>   Sponsored by:	EMC / Isilon Storage Division

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