Just five cents - exporting the offset (making it global) might have side
effect impacting the performance.
Offset might be located in some memory sharing the cacheline with some other
variables.
If these variables are writable and are being updated frequently - we might get
the cache contention.
I'd prefer to keep all dynamic offsets In the PMD and entirely control memory
allocation
attributes for these ones. Hence, exporting is OK, but practical usage in
datapath is questionable.
With best regards, Slava
> -----Original Message-----
> From: Andrew Rybchenko <andrew.rybche...@oktetlabs.ru>
> Sent: Thursday, October 29, 2020 13:02
> To: NBU-Contact-Thomas Monjalon <tho...@monjalon.net>; dev@dpdk.org
> Cc: ferruh.yi...@intel.com; david.march...@redhat.com;
> bruce.richard...@intel.com; olivier.m...@6wind.com; jer...@marvell.com;
> Slava Ovsiienko <viachesl...@nvidia.com>; Nithin Dabilpuram
> <ndabilpu...@marvell.com>; Kiran Kumar K <kirankum...@marvell.com>;
> Ray Kinsella <m...@ashroe.eu>; Neil Horman <nhor...@tuxdriver.com>
> Subject: Re: [PATCH 10/15] net/octeontx2: switch timestamp to dynamic mbuf
> field
>
> On 10/29/20 12:27 PM, Thomas Monjalon wrote:
> > The mbuf timestamp is moved to a dynamic field in order to allow
> > removal of the deprecated static field.
> > The related mbuf flag is also replaced.
> >
> > Signed-off-by: Thomas Monjalon <tho...@monjalon.net>
> > ---
> > drivers/net/octeontx2/otx2_ethdev.c | 33
> +++++++++++++++++++++++++++++
> > drivers/net/octeontx2/otx2_rx.h | 19 ++++++++++++++---
> > drivers/net/octeontx2/version.map | 7 ++++++
> > 3 files changed, 56 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/octeontx2/otx2_ethdev.c
> > b/drivers/net/octeontx2/otx2_ethdev.c
> > index cfb733a4b5..ad95219438 100644
> > --- a/drivers/net/octeontx2/otx2_ethdev.c
> > +++ b/drivers/net/octeontx2/otx2_ethdev.c
> > @@ -4,6 +4,7 @@
> >
> > #include <inttypes.h>
> >
> > +#include <rte_bitops.h>
> > #include <rte_ethdev_pci.h>
> > #include <rte_io.h>
> > #include <rte_malloc.h>
> > @@ -14,6 +15,35 @@
> > #include "otx2_ethdev.h"
> > #include "otx2_ethdev_sec.h"
> >
> > +uint64_t rte_pmd_octeontx2_timestamp_rx_dynflag;
> > +int rte_pmd_octeontx2_timestamp_dynfield_offset = -1;
> > +
> > +static int
> > +otx2_rx_timestamp_setup(uint16_t flags) {
> > + int timestamp_rx_dynflag_offset;
> > +
> > + if ((flags & NIX_RX_OFFLOAD_TSTAMP_F) == 0)
> > + return 0;
> > +
> > + rte_pmd_octeontx2_timestamp_dynfield_offset =
> rte_mbuf_dynfield_lookup(
> > + RTE_MBUF_DYNFIELD_TIMESTAMP_NAME, NULL);
> > + if (rte_pmd_octeontx2_timestamp_dynfield_offset < 0) {
> > + otx2_err("Failed to lookup timestamp field");
> > + return -rte_errno;
> > + }
> > + timestamp_rx_dynflag_offset = rte_mbuf_dynflag_lookup(
> > + RTE_MBUF_DYNFLAG_RX_TIMESTAMP_NAME, NULL);
> > + if (timestamp_rx_dynflag_offset < 0) {
> > + otx2_err("Failed to lookup Rx timestamp flag");
> > + return -rte_errno;
> > + }
> > + rte_pmd_octeontx2_timestamp_rx_dynflag =
> > + RTE_BIT64(timestamp_rx_dynflag_offset);
> > +
> > + return 0;
> > +}
> > +
> > static inline uint64_t
> > nix_get_rx_offload_capa(struct otx2_eth_dev *dev) { @@ -1874,6
> > +1904,9 @@ otx2_nix_configure(struct rte_eth_dev *eth_dev)
> > dev->tx_offload_flags |= nix_tx_offload_flags(eth_dev);
> > dev->rss_info.rss_grps = NIX_RSS_GRPS;
> >
> > + if (otx2_rx_timestamp_setup(dev->rx_offload_flags) != 0)
> > + goto fail_offloads;
> > +
> > nb_rxq = RTE_MAX(data->nb_rx_queues, 1);
> > nb_txq = RTE_MAX(data->nb_tx_queues, 1);
> >
> > diff --git a/drivers/net/octeontx2/otx2_rx.h
> > b/drivers/net/octeontx2/otx2_rx.h index 61a5c436dd..6981edce82 100644
> > --- a/drivers/net/octeontx2/otx2_rx.h
> > +++ b/drivers/net/octeontx2/otx2_rx.h
> > @@ -63,6 +63,18 @@ union mbuf_initializer {
> > uint64_t value;
> > };
> >
> > +/* variables are exported because this file is included in other
> > +drivers */ extern uint64_t rte_pmd_octeontx2_timestamp_rx_dynflag;
> > +extern int rte_pmd_octeontx2_timestamp_dynfield_offset;
> > +
> > +static inline rte_mbuf_timestamp_t *
> > +otx2_timestamp_dynfield(struct rte_mbuf *mbuf) {
> > + return RTE_MBUF_DYNFIELD(mbuf,
> > + rte_pmd_octeontx2_timestamp_dynfield_offset,
> > + rte_mbuf_timestamp_t *);
> > +}
> > +
>
> May be ethdev should provide the inline function?
Just five cents - exporting the offset (making it global) might have side
effect impacting the performance.
Offset might be located in some memory sharing the cacheline with some other
variables.
If these variables are writable and are being updated frequently - we might get
the cache contention.
I'd prefer to keep all dynamic offsets In the PMD and entirely control memory
allocation
attributes for these ones. Hence, exporting/inline function is possible,
but practical usage, say, in datapath, is questionable.
With best regards, Slava
