From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
To: "Björn Töpel" <bjorn.topel@intel.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
davem@davemloft.net
Cc: netdev@vger.kernel.org, nhorman@redhat.com, sassmann@redhat.com,
Andrew Bowers <andrewx.bowers@intel.com>
Subject: Re: [net-next 01/12] i40e: replace switch-statement to speed-up retpoline-enabled builds
Date: Thu, 02 May 2019 13:40:00 -0700 [thread overview]
Message-ID: <5e546c17ad929d97d6c4ca7d93b8f504da33dc31.camel@intel.com> (raw)
In-Reply-To: <0c73af48-d638-dd58-fcf8-c872ff8591d7@intel.com>
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On Thu, 2019-05-02 at 22:29 +0200, Björn Töpel wrote:
> On 2019-05-02 16:47, Daniel Borkmann wrote:
> > On 04/29/2019 09:16 PM, Jeff Kirsher 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.
> > >
> > > The if-clause was also refactored into a common function that can be
> > > used by AF_XDP zero-copy and non-zero-copy code.
> >
> > Isn't it fixed upstream by now already (also in gcc)?
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce02ef06fcf7a399a6276adb83f37373d10cbbe1
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a9d57ef15cbe327fe54416dd194ee0ea66ae53a4
> >
>
> Hmm, given that Daniel's work is upstream, this patch doesn't really
> make sense any more. OTOH it can stay in the series, and be cleaned up
> later.
>
> I'll leave it for you to decide, Jeff!
I am already making revisions to the series due to another patch, so if
these changes are no longer needed to improve performance in RETPOLINE
builds, then lets drop it.
Björn, can you confirm that with or without these changes, XDP performance
stays the same for RETPOLINE builds?
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next prev parent reply other threads:[~2019-05-02 20:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 19:16 [net-next 00/12][pull request] 40GbE Intel Wired LAN Driver Updates 2019-04-29 Jeff Kirsher
2019-04-29 19:16 ` [net-next 01/12] i40e: replace switch-statement to speed-up retpoline-enabled builds Jeff Kirsher
2019-04-29 20:01 ` Josh Elsasser
2019-04-30 10:42 ` David Laight
2019-05-06 8:43 ` Daniel Borkmann
2019-05-02 14:47 ` Daniel Borkmann
2019-05-02 20:29 ` Björn Töpel
2019-05-02 20:40 ` Jeff Kirsher [this message]
2019-05-02 20:56 ` Björn Töpel
2019-05-02 20:57 ` Jeff Kirsher
2019-04-29 19:16 ` [net-next 02/12] i40e: Fix for allowing too many MDD events on VF Jeff Kirsher
2019-04-29 19:16 ` [net-next 03/12] i40e: change behavior on PF in response to MDD event Jeff Kirsher
2019-04-29 19:16 ` [net-next 04/12] i40e: remove error msg when vf with port vlan tries to remove vlan 0 Jeff Kirsher
2019-04-29 19:16 ` [net-next 05/12] i40e: ShadowRAM checksum calculation change Jeff Kirsher
2019-04-29 19:16 ` [net-next 06/12] i40e: Report advertised link modes on 40GBase_LR4, CR4 and fibre Jeff Kirsher
2019-04-29 19:16 ` [net-next 07/12] i40e: Further implementation of LLDP Jeff Kirsher
2019-04-29 19:16 ` [net-next 08/12] i40e: remove out-of-range comparisons in i40e_validate_cloud_filter Jeff Kirsher
2019-04-29 19:16 ` [net-next 09/12] i40e: update version number Jeff Kirsher
2019-04-29 19:16 ` [net-next 10/12] i40e: fix misleading message about promisc setting on un-trusted VF Jeff Kirsher
2019-04-29 19:16 ` [net-next 11/12] i40e: print PCI vendor and device ID during probe Jeff Kirsher
2019-04-29 19:16 ` [net-next 12/12] i40e: Introduce recovery mode support Jeff Kirsher
2019-04-30 1:07 ` Jakub Kicinski
2019-05-02 9:20 ` Jeff Kirsher
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