re: CVS commit: src/sys/arch/sparc64/dev

[matthew green <mrg%eterna.com.au@localhost>]

   Module Name: src
   Committed By:        nakayama
   Date:                Mon Dec  7 11:14:27 UTC 2009
   
   Modified Files:
        src/sys/arch/sparc64/dev: iommu.c
   
   Log Message:
   Avoid use of iommu_dvmamap_unload in error path.  It is too
   expensive since it contains data cache flushing.
   
   Some driver (tlp(4) with DM9201 on Netra X1) can only handle one
   DMA segment, so it was called frequently.

+       /* How can this fail?  And if it does what can we do? */
+       err = extent_free(is->is_dvmamap, map->_dm_dvmastart, sgsize,
+           EX_NOWAIT);


this can fail almost any time.  it happens when there is no free
memory and to free a chunk would require to split a current extent
range into two.


.mrg.