From: Paul Menzel <pmenzel@molgen.mpg.de> To: "Björn Töpel" <bjorn.topel@intel.com>, intel-wired-lan@lists.osuosl.org Cc: netdev@vger.kernel.org, "Björn Töpel" <bjorn.topel@intel.com>, magnus.karlsson@gmail.com, magnus.karlsson@intel.com, brouer@redhat.com Subject: Re: [Intel-wired-lan] [PATCH] i40e: replace switch-statement with if-clause Date: Mon, 21 Jan 2019 17:42:02 +0100 [thread overview] Message-ID: <60f67e64-568c-bf04-5e9c-0429c5ae2882@molgen.mpg.de> (raw) In-Reply-To: <20190121163356.31332-1-bjorn.topel@gmail.com> [-- Attachment #1: Type: text/plain, Size: 2584 bytes --] Dear Björn, On 01/21/19 17:33, bjorn.topel@gmail.com wrote: > From: Björn Töpel <bjorn.topel@intel.com> > > GCC will generate jump tables for switch-statements with more than 5 > case statements. An entry into the jump table is an indirect call, > which means that for CONFIG_RETPOLINE builds, this is rather > expensive. > > This commit replaces the switch-statement that acts on the XDP program > result with an if-clause. Maybe mention the performance improvement already here. I’d also put it into the commit message summary. Something like: > i40e: Speed up retpoline case by using if-clause If that jump tables are a common problem, I wonder, why the compiler cannot be adapted to generate better performing code or an option passed to the compiler. > The if-clause was also refactored into a common function that can be > used by AF_XDP zero-copy and non-zero-copy code. > > Performance prior this patch: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 18983018 0 > XDP-RX CPU total 18983018 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 18983012 0 > rx_queue_index 20:sum 18983012 > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0@enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 14,641,496 144,751,092 > tx 0 0 > > And after: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 24000986 0 > XDP-RX CPU total 24000986 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 24000985 0 > rx_queue_index 20:sum 24000985 > > +26% > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0@enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 17,623,578 163,503,263 > tx 0 0 > > +20% > > Signed-off-by: Björn Töpel <bjorn.topel@intel.com> > --- > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 31 ++++--------------- > .../ethernet/intel/i40e/i40e_txrx_common.h | 27 ++++++++++++++++ > drivers/net/ethernet/intel/i40e/i40e_xsk.c | 24 ++------------ > 3 files changed, 35 insertions(+), 47 deletions(-) […] Kind regards, Paul [-- Attachment #2: S/MIME Cryptographic Signature --] [-- Type: application/pkcs7-signature, Size: 5174 bytes --]
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From: Paul Menzel <pmenzel@molgen.mpg.de> To: intel-wired-lan@osuosl.org Subject: [Intel-wired-lan] [PATCH] i40e: replace switch-statement with if-clause Date: Mon, 21 Jan 2019 17:42:02 +0100 [thread overview] Message-ID: <60f67e64-568c-bf04-5e9c-0429c5ae2882@molgen.mpg.de> (raw) In-Reply-To: <20190121163356.31332-1-bjorn.topel@gmail.com> Dear Bj?rn, On 01/21/19 17:33, bjorn.topel at gmail.com wrote: > From: Bj?rn T?pel <bjorn.topel@intel.com> > > GCC will generate jump tables for switch-statements with more than 5 > case statements. An entry into the jump table is an indirect call, > which means that for CONFIG_RETPOLINE builds, this is rather > expensive. > > This commit replaces the switch-statement that acts on the XDP program > result with an if-clause. Maybe mention the performance improvement already here. I?d also put it into the commit message summary. Something like: > i40e: Speed up retpoline case by using if-clause If that jump tables are a common problem, I wonder, why the compiler cannot be adapted to generate better performing code or an option passed to the compiler. > The if-clause was also refactored into a common function that can be > used by AF_XDP zero-copy and non-zero-copy code. > > Performance prior this patch: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 18983018 0 > XDP-RX CPU total 18983018 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 18983012 0 > rx_queue_index 20:sum 18983012 > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0 at enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 14,641,496 144,751,092 > tx 0 0 > > And after: > $ sudo ./xdp_rxq_info --dev enp134s0f0 --action XDP_DROP > Running XDP on dev:enp134s0f0 (ifindex:7) action:XDP_DROP options:no_touch > XDP stats CPU pps issue-pps > XDP-RX CPU 20 24000986 0 > XDP-RX CPU total 24000986 > > RXQ stats RXQ:CPU pps issue-pps > rx_queue_index 20:20 24000985 0 > rx_queue_index 20:sum 24000985 > > +26% > > $ sudo ./xdpsock -i enp134s0f0 -q 20 -n 2 -z -r > sock0 at enp134s0f0:20 rxdrop > pps pkts 2.00 > rx 17,623,578 163,503,263 > tx 0 0 > > +20% > > Signed-off-by: Bj?rn T?pel <bjorn.topel@intel.com> > --- > drivers/net/ethernet/intel/i40e/i40e_txrx.c | 31 ++++--------------- > .../ethernet/intel/i40e/i40e_txrx_common.h | 27 ++++++++++++++++ > drivers/net/ethernet/intel/i40e/i40e_xsk.c | 24 ++------------ > 3 files changed, 35 insertions(+), 47 deletions(-) [?] Kind regards, Paul -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 5174 bytes Desc: S/MIME Cryptographic Signature URL: <http://lists.osuosl.org/pipermail/intel-wired-lan/attachments/20190121/15b4cb01/attachment.p7s>
next prev parent reply other threads:[~2019-01-21 16:42 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-01-21 16:33 [PATCH] i40e: replace switch-statement with if-clause bjorn.topel 2019-01-21 16:33 ` [Intel-wired-lan] " bjorn.topel 2019-01-21 16:42 ` Paul Menzel [this message] 2019-01-21 16:42 ` Paul Menzel 2019-01-21 16:53 ` Björn Töpel 2019-01-21 16:53 ` =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?= 2019-01-21 19:12 ` Jesper Dangaard Brouer 2019-01-21 19:12 ` Jesper Dangaard Brouer 2019-01-22 6:51 ` Björn Töpel 2019-01-22 6:51 ` =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?= 2019-01-21 18:59 ` Jesper Dangaard Brouer 2019-01-21 18:59 ` [Intel-wired-lan] " Jesper Dangaard Brouer
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