On 05/07/2018 08:23 AM, Salvatore Mesoraca wrote: > We avoid 2 VLAs by using a pre-allocated field in dsa_switch. > We also try to avoid dynamic allocation whenever possible. > > Link: > http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qpxydaacu1rq...@mail.gmail.com > Link: http://lkml.kernel.org/r/20180505185145.gb32...@lunn.ch > > Signed-off-by: Salvatore Mesoraca <s.mesorac...@gmail.com> > --- > include/net/dsa.h | 3 +++ > net/dsa/dsa2.c | 14 ++++++++++++++ > net/dsa/switch.c | 22 ++++++++++------------ > 3 files changed, 27 insertions(+), 12 deletions(-) > > diff --git a/include/net/dsa.h b/include/net/dsa.h > index 60fb4ec..576791d 100644 > --- a/include/net/dsa.h > +++ b/include/net/dsa.h > @@ -256,6 +256,9 @@ struct dsa_switch { > /* Number of switch port queues */ > unsigned int num_tx_queues; > > + unsigned long *bitmap; > + unsigned long _bitmap; > + > /* Dynamically allocated ports, keep last */ > size_t num_ports; > struct dsa_port ports[]; > diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c > index adf50fb..cebf35f0 100644 > --- a/net/dsa/dsa2.c > +++ b/net/dsa/dsa2.c > @@ -748,6 +748,20 @@ struct dsa_switch *dsa_switch_alloc(struct device *dev, > size_t n) > if (!ds) > return NULL; > > + /* We avoid allocating memory outside dsa_switch > + * if it is not needed. > + */ > + if (n <= sizeof(ds->_bitmap) * 8) { > + ds->bitmap = &ds->_bitmap;
Should not this be / BITS_PER_BYTE? If the sizeof(unsigned long) is <= 8, then you don't need to allocate it, otherwise, you have to. I would actually just always dynamically allocate the bitmap, optimizing for the case where we have fewer than or 8 ports is not worth IMHO. -- Florian
