Re: [Qemu-devel] [PATCH v2 1/1] socket: Allocating Large sized arrays to heap

[Daniel P. Berrange]

On Mon, Mar 14, 2016 at 10:44:22PM +0530, Pooja Dhannawat wrote:
> On Mon, Mar 14, 2016 at 10:20 PM, Daniel P. Berrange <address@hidden>
> wrote:
> 
> > On Mon, Mar 14, 2016 at 10:07:53PM +0530, Pooja Dhannawat wrote:
> > > net_socket_send has a huge stack usage of 69712 bytes approx.
> > > Moving large arrays to heap to reduce stack usage.
> > >
> > > Signed-off-by: Pooja Dhannawat <address@hidden>
> > > ---
> > >  net/socket.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/net/socket.c b/net/socket.c
> > > index e32e3cb..3fcd7a6 100644
> > > --- a/net/socket.c
> > > +++ b/net/socket.c
> > > @@ -147,10 +147,10 @@ static void net_socket_send(void *opaque)
> > >      NetSocketState *s = opaque;
> > >      int size, err;
> > >      unsigned l;
> > > -    uint8_t buf1[NET_BUFSIZE];
> > > +    uint8_t *buf1 = g_new(uint8_t, NET_BUFSIZE);
> >
> > You're allocating NET_BUFSIZE worth of uint8_t's
> >
> > I didn't get you clear.
> 
> 
> > >      const uint8_t *buf;
> > >
> > > -    size = qemu_recv(s->fd, buf1, sizeof(buf1), 0);
> > > +    size = qemu_recv(s->fd, (uint8_t *)buf1, sizeof(uint8_t), 0);
> >
> > But only reading 1 byte which is clearly wrong. You likely wanted
> > NET_BUFSIZE here, not sizeof(uint8_t)
> >
> > Correct me If I am wrong. This should also work :
> size = qemu_recv(s->fd, (uint8_t *)buf1, NET_BUFSIZE * sizeof(uint8_t), 0);

Sure, if you want to add a pointless 'multiply by 1' to the code,
which you didn't bother doing for the g_new call.


Regards,
Daniel
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