Re: [dpdk-dev] [dpdk-stable] [PATCH v2] net/i40e: fix incorrect byte counters

["Jiang, JunyuX" <junyux.jiang@intel.com>]

Hi Ferruh,

> -----Original Message-----
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> Sent: Friday, September 18, 2020 9:42 PM
> To: Igor Ryzhov <iryzhov@nfware.com>; Jiang, JunyuX
> <junyux.jiang@intel.com>
> Cc: dev@dpdk.org; Guo, Jia <jia.guo@intel.com>; Xing, Beilei
> <beilei.xing@intel.com>; stable@dpdk.org
> Subject: Re: [dpdk-dev] [dpdk-stable] [PATCH v2] net/i40e: fix incorrect byte
> counters
> 
> On 9/18/2020 10:23 AM, Igor Ryzhov wrote:
> > Hi,
> >
> > Your code will work only if stats are updated at least once between
> > two overflows.
>  >
> 
> In this case it will have problems in 'i40e_stat_update_48()' too.
> It seems there is no way to detect if the increase in stats is N or MAX_48+N
> by the software.
> And obviously there is no way to detect if the overflow occurred more than
> once.
> 
> > So it's still up to the application to handle this properly. I think
> > it should be mentioned in the docs.
> >
> 
> +1 to document.
> 
I will fix in V3.
> > Igor
> >
> > On Fri, Sep 18, 2020 at 6:45 AM Jiang, JunyuX <junyux.jiang@intel.com
> > <mailto:junyux.jiang@intel.com>> wrote:
> >
> >     Hi Ferruh,
> >
> >      > -----Original Message-----
> >      > From: Ferruh Yigit <ferruh.yigit@intel.com
> >     <mailto:ferruh.yigit@intel.com>>
> >      > Sent: Wednesday, September 16, 2020 8:31 PM
> >      > To: Jiang, JunyuX <junyux.jiang@intel.com
> >     <mailto:junyux.jiang@intel.com>>; dev@dpdk.org
> <mailto:dev@dpdk.org>
> >      > Cc: Guo, Jia <jia.guo@intel.com <mailto:jia.guo@intel.com>>;
> >     Xing, Beilei <beilei.xing@intel.com <mailto:beilei.xing@intel.com>>;
> >      > stable@dpdk.org <mailto:stable@dpdk.org>
> >      > Subject: Re: [dpdk-stable] [PATCH v2] net/i40e: fix incorrect
> >     byte counters
> >      >
> >      > On 9/16/2020 2:51 AM, Junyu Jiang wrote:
> >      > > This patch fixed the issue that rx/tx bytes overflowed
> >      >
> >      > "Rx/Tx statistics counters overflowed"?
> >      >
> >     Yes, the rx_bytes and tx_bytes counter in X710 cards is 48-bit long,
> >     if keep sending packets for a log time, the register will overflow.
> >
> >      > > on 48 bit limitation by enlarging the limitation.
> >      > >
> >      > > Fixes: 4861cde46116 ("i40e: new poll mode driver")
> >      > > Cc: stable@dpdk.org <mailto:stable@dpdk.org>
> >      > >
> >      > > Signed-off-by: Junyu Jiang <junyux.jiang@intel.com
> >     <mailto:junyux.jiang@intel.com>>
> >      > > ---
> >      > >   drivers/net/i40e/i40e_ethdev.c | 47
> >      > ++++++++++++++++++++++++++++++++++
> >      > >   drivers/net/i40e/i40e_ethdev.h |  9 +++++++
> >      > >   2 files changed, 56 insertions(+)
> >      > >
> >      > > diff --git a/drivers/net/i40e/i40e_ethdev.c
> >      > > b/drivers/net/i40e/i40e_ethdev.c index 563f21d9d..4d4ea9861
> 100644
> >      > > --- a/drivers/net/i40e/i40e_ethdev.c
> >      > > +++ b/drivers/net/i40e/i40e_ethdev.c
> >      > > @@ -3073,6 +3073,13 @@ i40e_update_vsi_stats(struct i40e_vsi *vsi)
> >      > >     i40e_stat_update_48(hw, I40E_GLV_BPRCH(idx),
> >      > I40E_GLV_BPRCL(idx),
> >      > >                         vsi->offset_loaded, &oes->rx_broadcast,
> >      > >                         &nes->rx_broadcast);
> >      > > +   /* enlarge the limitation when rx_bytes overflowed */
> >      > > +   if (vsi->offset_loaded) {
> >      > > +           if (I40E_RXTX_BYTES_LOW(vsi->old_rx_bytes) > nes-
> >      > >rx_bytes)
> >      > > +                   nes->rx_bytes += (uint64_t)1 <<
> >     I40E_48_BIT_WIDTH;
> >      > > +           nes->rx_bytes += I40E_RXTX_BYTES_HIGH(vsi-
> >      > >old_rx_bytes);
> >      > > +   }
> >      > > +   vsi->old_rx_bytes = nes->rx_bytes;
> >      >
> >      >
> >      > Can you please describe this logic? (indeed better to describe it
> >     in the
> >      > commit log)
> >      >
> >      > 'nes->rx_bytes' is diff in the stats register since last read.
> >      > 'old_rx_bytes' is the previous stats diff.
> >      >
> >      > Why/how "I40E_RXTX_BYTES_LOW(vsi->old_rx_bytes) > nes-
> >rx_bytes" has
> >      > a meaning? Isn't this very depends on the read frequency?
> >      >
> >      > I guess I am missing something but please help me understand.
> >      >
> >     This patch fixes the issue of rx/tx bytes counter register overflow:
> >     The counter register in i40e is 48-bit long, when overflow,
> >     nes->rx_bytes becomes less than old_rx_bytes, the correct value of
> >     nes->rx_bytes should be plused 1 << 48.
> >     Use I40E_RXTX_BYTES_HIGH() to remember the MSB, nes->rx_bytes
> plus
> >     the MSB is the correct value, So that using uint64_t to enlarge the
> >     48 bit  limitation of register .
> >
> >      > Also can you please confirm the initial value of the
> >     "vsi->offset_loaded" is
> >      > correct.
> >      >
> >     offset_loaded will be true when get statistics of  port and
> >     offset_loaded will be false when reset or clear the statistics,
> >     so if  offset_loaded is false, shouldn't to calculate the value of
> >     nes->rx_bytes, it will be 0.
> >
> >      > <....>
> >      >
> >      > > @@ -282,6 +282,9 @@ struct rte_flow {
> >      > >   #define I40E_ETH_OVERHEAD \
> >      > >     (RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN +
> >      > I40E_VLAN_TAG_SIZE * 2)
> >      > >
> >      > > +#define I40E_RXTX_BYTES_HIGH(bytes) ((bytes) &
> ~I40E_48_BIT_MASK)
> >      > > +#define I40E_RXTX_BYTES_LOW(bytes) ((bytes) &
> I40E_48_BIT_MASK)
> >      > > +
> >      >
> >      > HIGH/LOW is a little misleading, for 64Bits it sounds like it is
> >     getting low 32 bits
> >      > and high 32 bits, can you please clarify macro masks out
> >      > 48/16 bits.
> >      >
> >     Yes, I will change the macro name in V3.
> >      >
> >      > >   struct i40e_adapter;
> >      > >   struct rte_pci_driver;
> >      > >
> >      > > @@ -399,6 +402,8 @@ struct i40e_vsi {
> >      > >     uint8_t vlan_anti_spoof_on; /* The VLAN anti-spoofing
> >     enabled */
> >      > >     uint8_t vlan_filter_on; /* The VLAN filter enabled */
> >      > >     struct i40e_bw_info bw_info; /* VSI bandwidth information */
> >      > > +   uint64_t old_rx_bytes;
> >      > > +   uint64_t old_tx_bytes;
> >      >
> >      > 'prev' seems better naming than 'old', what do you think renaming
> >      > 'old_rx_bytes' -> 'prev_rx_bytes' (for all variables)?
> >     Yes, it's better, I will fix it in V3.
> >