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    SubjectRe: [PATCH 00/53] dyn_array/nr_irqs/sparse_irq support v10
    On Thu, Aug 14, 2008 at 6:26 AM, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > (lkml Cc:-ed)
    >
    > * Yinghai Lu <yhlu.kernel@gmail.com> wrote:
    >
    >> v10: make the x86 32 bit support sparse_irq too.
    >> also make remove irqbalance in kernel for 32 bit
    >> and make 32 bit support per_cpu vector. so start merging or io_apic_xx.c
    >>
    >> 01-03 is some fix for current tree
    >> 04: is revert for one patch hide in sched/ and tip/master
    >>
    >> based on tip/master
    >>
    >> to do:
    >> merge io_apic_xx.c
    >
    > ok, i've created a new tip/irq/sparseirq topic branch for this.
    >
    > Could you please send future updates against:
    >
    > git-checkout tip/master
    > git-merge tip/irq/sparseirq
    >
    > Not yet integrated into tip/master, i've still got some other backlog.
    >
    > A couple of observations about the general structure of the sparse irqs
    > code:
    >
    > - the new APIs should probably live in mm/bootmem.c not in init/main.c,
    > and in bootmem.h. Also, it should be outlined clearly why this new API
    > is needed as a wrapper ontop of existing bootmem mechanisms.

    move
    pre_alloc_dyn_array, per_cpu_dyn_array_size, per_cpu_alloc_dyn_array
    to mm/bootmem.c?

    >
    > - the #ifdef complications, while fine for migration, should be
    > eliminated. Could we introduce some compatible form for the
    > definition/allocation APIs that work even if an architecture still
    > uses a flat irq array? That would remove most of the uglinesses.
    # git grep CONFIG_HAVE_DYN_ARRAY | wc -l
    9

    #git grep CONFIG_HAVE_SPARSE_IRQ | wc -l
    39

    arch/x86/kernel/io_apic_32.c:#ifdef CONFIG_HAVE_SPARSE_IRQ_DEBUG
    arch/x86/kernel/io_apic_32.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    arch/x86/kernel/io_apic_64.c:#ifdef CONFIG_HAVE_SPARSE_IRQ_DEBUG
    arch/x86/kernel/io_apic_64.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    arch/x86/kernel/irq_32.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    arch/x86/kernel/irq_64.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    drivers/char/random.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    drivers/char/random.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    drivers/pci/intr_remapping.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    drivers/pci/intr_remapping.c:#else /* !CONFIG_HAVE_SPARSE_IRQ */
    drivers/pci/intr_remapping.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    fs/proc/proc_misc.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    fs/proc/proc_misc.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    fs/proc/proc_misc.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    include/linux/irq.h:#ifdef CONFIG_HAVE_SPARSE_IRQ
    include/linux/irq.h:#ifdef CONFIG_HAVE_SPARSE_IRQ
    include/linux/irq.h:#ifdef CONFIG_HAVE_SPARSE_IRQ
    include/linux/irq.h:#ifdef CONFIG_HAVE_SPARSE_IRQ
    include/linux/irq.h:#if defined(CONFIG_INTR_REMAP) &&
    defined(CONFIG_HAVE_SPARSE_IRQ)
    include/linux/irq.h:#ifndef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/chip.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/chip.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/chip.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/chip.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/chip.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ_DEBUG
    kernel/irq/handle.c:#ifndef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/handle.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/manage.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/manage.c:#ifdef CONFIG_HAVE_SPARSE_IRQ
    kernel/irq/migration.c:#ifdef CONFIG_HAVE_SPARSE_IRQ

    because try to avoid more api to be changed to take irq_desc as parameter.

    >
    > - some of the irq < 16 checks in x86 look a bit ugly, can we do anything
    > about them?

    is_legacy_irq(irq) ? or legacy_irq(irq)?

    >
    > - i think as a final-ish commit we should just remove the dyn-array
    > define and make all architectures use this facility. You converted
    > most of them - how many are still missing? Sparse-irq is more
    > intrusive so that should probably stay a Kconfig knob.

    so when config_sparse_irq is not selected, need to use dyn_array to
    allocate irq_desc and irq_cfg, or just static array?

    >
    > - there was one aspect of NR_IRQS that was nice and useful: it acted as
    > a sanity check against BIOS bugs and driver bugs that pass in some
    > irrealistically high irq number. Now we'll just try to allocate some
    > really high IRQ and accept it. I _think_ there should be a single,
    > simple 'absolute maximum IRQ number' define which should set the
    > maximum possible IRQ number. Lets call it NR_IRQS_MAX or so, and set
    > it to NR_CPUS*NR_IO_APICS*224 or so?

    when sparse_irq is used, irq is [0, -1U]
    driver could be irq_desc(irq) to check if irq is valid or not. and use
    irq_desc_with_new(new) to get a new one.

    when generic_hardirqs is not used (s390, m68k, sparc), we need to
    create some stubs in linux/interrupt.h for them

    >
    > - i'm a bit worried about linecount increase in general:
    >
    > 247 files changed, 3671 insertions(+), 2052 deletions(-)
    >
    > could we work on reducing that somewhat? The new infrastructure bits
    > in mm/* and kernel/irq/* will be unavoidable, what we should
    > concentrate on is to make usage of the new facility just as
    > straightforward, easy and compact as the old irq_desc[] usages.
    before that we could use get_irq_desc() and get_irq_desc_without_new()
    and according to eric, i changed that to irq_desc_with_new and irq_desc().

    so the array irq_desc[] need to be changed to irq_descX[]
    ( or *irq_desc to *irq_descX for dyn_array)
    >
    > A worst-case example is drivers/char/random.c: the
    > CONFIG_HAVE_SPARSE_IRQ and CONFIG_HAVE_DYN_ARRAY #ifdef jungle is not
    > acceptable. I think the best way out is to convert the whole kernel to
    > the new facilities (as safely as possible, without breaking other
    > architectures), and making sure that the end result is easy to
    > understand and intuitive.

    # grep CONFIG_HAVE_ drivers/char/random.c
    #ifndef CONFIG_HAVE_SPARSE_IRQ
    #ifdef CONFIG_HAVE_DYN_ARRAY
    #ifndef CONFIG_HAVE_SPARSE_IRQ

    just want to make other arch is untouched.

    >
    > so i dont mind the current code as long as the extra complications are
    > temporary during a safe conversion - but we should work on eliminating
    > all those complications before thinking about upstream merging.
    >
    > Ingo
    >
    > -------------------->
    > the irq/sparseirq git tree can be picked up from:
    >
    > git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git irq/sparseirq
    >

    Thanks

    Yinghai Lu


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