linux-kernel - Re: [PATCH 5/5] genirq: Use the maple tree for IRQ descriptors management

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Message-ID: <87edrb115j.ffs@tglx>
Date:   Tue, 31 Jan 2023 10:52:40 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Shanker Donthineni <sdonthineni@...dia.com>,
        Marc Zyngier <maz@...nel.org>, Michael Walle <michael@...le.cc>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Hans de Goede <hdegoede@...hat.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Shanker Donthineni <sdonthineni@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] genirq: Use the maple tree for IRQ descriptors
 management

On Sun, Jan 29 2023 at 18:57, Shanker Donthineni wrote:
> The current implementation uses a static bitmap and a radix tree
> to manage IRQ allocation and irq_desc pointer store respectively.
> However, the size of the bitmap is constrained by the build time
> macro MAX_SPARSE_IRQS, which may not be sufficient to support the
> high-end servers, particularly those with GICv4.1 hardware, which
> require a large interrupt space to cover LPIs and vSGIs
>
> The maple tree is a highly efficient data structure for storing
> non-overlapping ranges and can handle a large number of entries,
> up to ULONG_MAX. It can be utilized for both storing IRQD and

IRQD ??. Please write it out: interrupt descriptors

Changelogs have no space constraints and there is zero value to
introduce unreadable acronyms.

>  static DEFINE_MUTEX(sparse_irq_lock);
> -static DECLARE_BITMAP(allocated_irqs, MAX_SPARSE_IRQS);
> +static struct maple_tree sparse_irqs = MTREE_INIT_EXT(sparse_irqs,
> +					MT_FLAGS_ALLOC_RANGE |
> +					MT_FLAGS_LOCK_EXTERN |
> +					MT_FLAGS_USE_RCU, sparse_irq_lock);

Nit. Can we please format this properly:

static struct maple_tree sparse_irqs = MTREE_INIT_EXT(sparse_irqs,
						      MT_FLAGS_ALLOC_RANGE |
					              MT_FLAGS_LOCK_EXTERN |
					              MT_FLAGS_USE_RCU,
                                                      sparse_irq_lock);

Other than that this looks really good.

Thanks,

        tglx