lkml.org 
[lkml]   [2021]   [Jul]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Subject[PATCH v4 00/14] genirq: Cleanup the usage of irq_set_affinity_hint
    Date
    The drivers currently rely on irq_set_affinity_hint() to either set the
    affinity_hint that is consumed by the userspace and/or to enforce a custom
    affinity.

    irq_set_affinity_hint() as the name suggests is originally introduced to
    only set the affinity_hint to help the userspace in guiding the interrupts
    and not the affinity itself. However, since the commit

    e2e64a932556 "genirq: Set initial affinity in irq_set_affinity_hint()"

    irq_set_affinity_hint() also started applying the provided cpumask (if not
    NULL) as the affinity for the interrupts. The issue that this commit was
    trying to solve is to allow the drivers to enforce their affinity mask to
    distribute the interrupts across the CPUs such that they don't always end
    up on CPU0. This issue has been resolved within the irq subsystem since the
    commit

    a0c9259dc4e1 "irq/matrix: Spread interrupts on allocation"

    Hence, there is no need for the drivers to overwrite the affinity to spread
    as it is dynamically performed at the time of allocation.

    Also, irq_set_affinity_hint() setting affinity unconditionally introduces
    issues for the drivers that only want to set their affinity_hint and not the
    affinity itself as for these driver interrupts the default_smp_affinity_mask
    is completely ignored (for detailed investigation please refer to [1]).

    Unfortunately reverting the commit e2e64a932556 is not an option at this
    point for two reasons [2]:

    - Several drivers for a valid reason (performance) rely on this API to
    enforce their affinity mask

    - Until very recently this was the only exported interface that was
    available

    To clear this out Thomas has come up with the following interfaces:

    - irq_set_affinity(): only sets affinity of an IRQ [3]
    - irq_update_affinity_hint(): Only sets the hint [4]
    - irq_set_affinity_and_hint(): Sets both affinity and the hint mask [4]

    The first API is already merged in the linus's tree and the patch
    that introduces the other two interfaces is included with this patch-set.

    To move to the stage where we can safely get rid of the
    irq_set_affinity_hint(), which has been marked deprecated, we have to
    move all its consumers to these new interfaces. In this patch-set, I have
    done that for a few drivers and will hopefully try to move the remaining of
    them in the coming days.

    Testing
    -------
    In terms of testing, I have performed some basic testing on x86 to verify
    things such as the interrupts are evenly spread on all CPUs, hint mask is
    correctly set etc. for the drivers - i40e, iavf, mlx5, mlx4, ixgbe, and
    enic on top of:

    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git

    So more testing is probably required for these and the drivers that I didn't
    test and any help will be much appreciated.


    Notes
    -----
    - For the mpt3sas driver I decided to go with the usage of
    irq_set_affinity_and_hint over irq_set_affinity based on my analysis of
    it and the megaraid driver. However, if we are sure that it is not
    required then I can replace it with just irq_set_affinity as one of its
    comment suggests.

    Change from v3 [5]
    ------------------
    - Replaced irq_set_affinity_and_hint with irq_update_affinity_hint in
    irdma (Leon Romanovsky)
    - rebased the patches on top of 5.14-rc2


    Change from v2 [6]
    ------------------

    - Rebased on top of 5.14-rc1 (Leon Romanovsky)
    + After discussion with Leon [7], made changes in the mlx5 patch to use
    irq_set_affinity_and_hint over irq_update_affinity_hint
    + i40iw is replaced with irdma driver, hence made the respective changes
    in irdma (also replcaed irq_update_affinity_hint with
    irq_set_affinity_and_hint).

    Change from v1 [8]
    ------------------
    - Fixed compilation error by adding the new interface definitions for cases
    where CONFIG_SMP is not defined

    - Fixed function usage in megaraid_sas and removed unnecessary variable
    (Robin Murphy)

    - Removed unwanted #if/endif from mlx4 (Leon Romanovsky)

    - Other indentation related fixes


    [1] https://lore.kernel.org/lkml/1a044a14-0884-eedb-5d30-28b4bec24b23@redhat.com/
    [2] https://lore.kernel.org/linux-pci/d1d5e797-49ee-4968-88c6-c07119343492@arm.com/
    [3] https://lore.kernel.org/linux-arm-kernel/20210518091725.046774792@linutronix.de/
    [4] https://lore.kernel.org/patchwork/patch/1434326/
    [5] https://lore.kernel.org/linux-scsi/20210713211502.464259-1-nitesh@redhat.com/
    [6] https://lore.kernel.org/lkml/20210629152746.2953364-1-nitesh@redhat.com/
    [7] https://lore.kernel.org/lkml/YO0eKv2GJcADQTHH@unreal/
    [8] https://lore.kernel.org/linux-scsi/20210617182242.8637-1-nitesh@redhat.com/

    Nitesh Narayan Lal (13):
    iavf: Use irq_update_affinity_hint
    i40e: Use irq_update_affinity_hint
    scsi: megaraid_sas: Use irq_set_affinity_and_hint
    scsi: mpt3sas: Use irq_set_affinity_and_hint
    RDMA/irdma: Use irq_update_affinity_hint
    enic: Use irq_update_affinity_hint
    be2net: Use irq_update_affinity_hint
    ixgbe: Use irq_update_affinity_hint
    mailbox: Use irq_update_affinity_hint
    scsi: lpfc: Use irq_set_affinity
    hinic: Use irq_set_affinity_and_hint
    net/mlx5: Use irq_set_affinity_and_hint
    net/mlx4: Use irq_update_affinity_hint

    Thomas Gleixner (1):
    genirq: Provide new interfaces for affinity hints

    drivers/infiniband/hw/irdma/hw.c | 4 +-
    drivers/mailbox/bcm-flexrm-mailbox.c | 4 +-
    drivers/net/ethernet/cisco/enic/enic_main.c | 8 +--
    drivers/net/ethernet/emulex/benet/be_main.c | 4 +-
    drivers/net/ethernet/huawei/hinic/hinic_rx.c | 4 +-
    drivers/net/ethernet/intel/i40e/i40e_main.c | 8 +--
    drivers/net/ethernet/intel/iavf/iavf_main.c | 8 +--
    drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 10 ++--
    drivers/net/ethernet/mellanox/mlx4/eq.c | 8 ++-
    .../net/ethernet/mellanox/mlx5/core/pci_irq.c | 8 +--
    drivers/scsi/lpfc/lpfc_init.c | 4 +-
    drivers/scsi/megaraid/megaraid_sas_base.c | 27 +++++-----
    drivers/scsi/mpt3sas/mpt3sas_base.c | 21 ++++----
    include/linux/interrupt.h | 53 ++++++++++++++++++-
    kernel/irq/manage.c | 8 +--
    15 files changed, 114 insertions(+), 65 deletions(-)

    --


    \
     
     \ /
      Last update: 2021-07-19 20:40    [W:4.008 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site