RE: [PATCH v2 1/1] net/colo-compare.c: Fix memory leak in packet_enqueue()

[Zhang, Chen]

> -----Original Message-----
> From: Jing-Wei Su <address@hidden>
> Sent: Tuesday, March 24, 2020 10:47 AM
> To: Zhang, Chen <address@hidden>
> Cc: address@hidden; address@hidden;
> address@hidden; address@hidden
> Subject: Re: [PATCH v2 1/1] net/colo-compare.c: Fix memory leak in
> packet_enqueue()
> 
> Zhang, Chen <address@hidden> 於 2020年3月24日 週二 上午3:24
> 寫道：
> >
> >
> >
> > > -----Original Message-----
> > > From: Derek Su <address@hidden>
> > > Sent: Monday, March 23, 2020 1:48 AM
> > > To: address@hidden
> > > Cc: Zhang, Chen <address@hidden>; address@hidden;
> > > address@hidden; address@hidden
> > > Subject: [PATCH v2 1/1] net/colo-compare.c: Fix memory leak in
> > > packet_enqueue()
> > >
> > > The patch is to fix the "pkt" memory leak in packet_enqueue().
> > > The allocated "pkt" needs to be freed if the colo compare primary or
> > > secondary queue is too big.
> >
> > Hi Derek,
> >
> > Thank you for the patch.
> > I re-think this issue in a big view, looks just free the pkg is not enough 
> > in
> this situation.
> > The root cause is network is too busy to compare, So, better choice is
> > notify COLO frame to do a checkpoint and clean up all the network
> > queue. This work maybe decrease COLO network performance but seams
> better than drop lots of pkg.
> >
> > Thanks
> > Zhang Chen
> >
> 
> Hello, Zhang
> 
> Got it.
> What is the concern of the massive "drop packets"?
> Does the behavior make the COLO do checkpoint periodically (~20 seconds)
> instead of doing immediate checkpoint when encountering different
> response packets?

The concern of the "drop packets" is guest will lose network connection with
most of real clients until next periodic force checkpoint. COLO designed for 
dynamic
control checkpoint, so I think do a checkpoint here will help guest supply 
service faster.

> 
> It seems that frequent checkpoints caused by the full queue (busy
> network) instead of different
> response packets may harm the high speed network (10 Gbps or higher)
> performance dramatically.

Yes, maybe I can send a patch to make user adjust queue size depend on it's own 
environment.
But with larger queue size, colo-compare will spend much time to do compare 
packet when network
Is real busy status.

Thanks
Zhang Chen   

> 
> Thanks
> Derek
> 
> > >
> > > Signed-off-by: Derek Su <address@hidden>
> > > ---
> > >  net/colo-compare.c | 23 +++++++++++++++--------
> > >  1 file changed, 15 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/net/colo-compare.c b/net/colo-compare.c index
> > > 7ee17f2cf8..cdd87b2aa8 100644
> > > --- a/net/colo-compare.c
> > > +++ b/net/colo-compare.c
> > > @@ -120,6 +120,10 @@ enum {
> > >      SECONDARY_IN,
> > >  };
> > >
> > > +static const char *colo_mode[] = {
> > > +    [PRIMARY_IN] = "primary",
> > > +    [SECONDARY_IN] = "secondary",
> > > +};
> > >
> > >  static int compare_chr_send(CompareState *s,
> > >                              const uint8_t *buf, @@ -215,6 +219,7 @@
> > > static int packet_enqueue(CompareState *s, int mode, Connection
> **con)
> > >      ConnectionKey key;
> > >      Packet *pkt = NULL;
> > >      Connection *conn;
> > > +    int ret;
> > >
> > >      if (mode == PRIMARY_IN) {
> > >          pkt = packet_new(s->pri_rs.buf, @@ -243,16 +248,18 @@
> > > static int packet_enqueue(CompareState *s, int mode, Connection
> **con)
> > >      }
> > >
> > >      if (mode == PRIMARY_IN) {
> > > -        if (!colo_insert_packet(&conn->primary_list, pkt, &conn->pack)) {
> > > -            error_report("colo compare primary queue size too big,"
> > > -                         "drop packet");
> > > -        }
> > > +        ret = colo_insert_packet(&conn->primary_list, pkt,
> > > + &conn->pack);
> > >      } else {
> > > -        if (!colo_insert_packet(&conn->secondary_list, pkt, 
> > > &conn->sack)) {
> > > -            error_report("colo compare secondary queue size too big,"
> > > -                         "drop packet");
> > > -        }
> > > +        ret = colo_insert_packet(&conn->secondary_list, pkt,
> > > + &conn->sack);
> > >      }
> > > +
> > > +    if (!ret) {
> > > +        error_report("colo compare %s queue size too big,"
> > > +                     "drop packet", colo_mode[mode]);
> > > +        packet_destroy(pkt, NULL);
> > > +        pkt = NULL;
> > > +    }
> > > +
> > >      *con = conn;
> > >
> > >      return 0;
> > > --
> > > 2.17.1
> >