Re: [Qemu-block] [Qemu-devel] [PATCH 2/2] virtio-blk: Inline request init, complete and free functions

[Stefan Hajnoczi]

On Tue, Feb 07, 2017 at 02:52:38PM +0100, Laszlo Ersek wrote:
> On 02/07/17 14:27, Fam Zheng wrote:
> > These are used in each request handling, inline them.
> > 
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> >  hw/block/virtio-blk.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> > index 2858c31..1da9570 100644
> > --- a/hw/block/virtio-blk.c
> > +++ b/hw/block/virtio-blk.c
> > @@ -29,8 +29,8 @@
> >  #include "hw/virtio/virtio-bus.h"
> >  #include "hw/virtio/virtio-access.h"
> >  
> > -static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq,
> > -                                    VirtIOBlockReq *req)
> > +static inline void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq,
> > +                                           VirtIOBlockReq *req)
> >  {
> >      req->dev = s;
> >      req->vq = vq;
> > @@ -40,12 +40,13 @@ static void virtio_blk_init_request(VirtIOBlock *s, 
> > VirtQueue *vq,
> >      req->mr_next = NULL;
> >  }
> >  
> > -static void virtio_blk_free_request(VirtIOBlockReq *req)
> > +static inline void virtio_blk_free_request(VirtIOBlockReq *req)
> >  {
> >      g_free(req);
> >  }
> >  
> > -static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char 
> > status)
> > +static inline void virtio_blk_req_complete(VirtIOBlockReq *req,
> > +                                           unsigned char status)
> >  {
> >      VirtIOBlock *s = req->dev;
> >      VirtIODevice *vdev = VIRTIO_DEVICE(s);
> > 
> 
> Hm, virtio_blk_req_complete() looks a bit too "meaty" and seems to be
> called from a little too many places for me to feel convenient about
> inlining it. I guess I'd leave it to the compiler to optimize the
> function call. Does the explicit hint offer a noticeable perf improvement?
> 
> Inlining virtio_blk_free_request() looks reasonable.
> 
> virtio_blk_init_request() looks okay too.
> 
> Other reviewers should feel free to override my concerns :) My view on
> this is distant.

I'm not a big fan of manually inlining functions.  Let the compiler
decide whether these static functions should be inlined.

Stefan

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