[ovs-dev] [PATCH] datapath: Increase maximum allocation size of action list.

Ben Pfaff blp at nicira.com
Mon Feb 25 19:00:23 UTC 2013


On Mon, Feb 25, 2013 at 10:58:53AM -0800, Jesse Gross wrote:
> On Mon, Feb 25, 2013 at 10:51 AM, Ben Pfaff <blp at nicira.com> wrote:
> > On Fri, Feb 22, 2013 at 12:28:14PM -0800, Jesse Gross wrote:
> >> The switch to flow based tunneling increased the size of each output
> >> action in the flow action list.  In extreme cases, this can result
> >> in the action list exceeding the maximum buffer size.
> >>
> >> This doubles the maximum buffer size to compensate for the increase
> >> in action size.  Since the buffer is potentially very large, it also
> >> switches to vmalloc.  In the common case, most allocations will be
> >> less than a page and vmalloc automatically uses kmalloc in that case.
> >> Therefore, for the majority of situations, this will have no impact.
> >>
> >> Bug #15203
> >>
> >> Signed-off-by: Jesse Gross <jesse at nicira.com>
> >
> > Are you sure that vmalloc() automatically uses kmalloc() for small
> > allocations?  Looking at 2.6.32 and 3.2, it appears to me that even
> > vmalloc(1) actually allocates at least 2 pages plus a small control
> > block.
> 
> No, I was wrong about that.  Pravin updated and fixed this patch,
> which has already been applied.

I see.  Thanks.



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