differences between M_CACHE, M_DEVBUF, M_TEMP

Daniel O'Connor doconnor at gsoft.com.au
Wed May 10 00:01:50 UTC 2006

On Tuesday 09 May 2006 08:29, Bharma Ji wrote:
> I am trying to understand the difference in these three different memories.
> Code comments in kern_malloc.c says that M_DEVBUF should be used for device
> driver. I didn't however see any major difference between the three
> memories. Can a device theoretically take up memory from  M_TEMP (or
> M_CACHE) segment? Similary can device drivers using M_DEVBUF also allocate
> from M_CACHE / M_TEMP if needed.

The M_* stuff is just a categorisation for memory allocations. Run vmstat -m 
to see what I mean.

AFAIK the actual take has no bearing on the performance of the allocation 

Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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