From: Julien Grall <julien.grall@arm.com>
To: Jiandi An <anjiandi@codeaurora.org>, xen-devel@lists.xen.org
Cc: sstabellini@kernel.org, shankerd@codeaurora.org
Subject: Re: [PATCH] arm/domain: allocate pages according to the order of struct domain size
Date: Wed, 8 Jun 2016 10:26:10 +0100 [thread overview]
Message-ID: <63e8d832-8d54-311e-aae4-c65ad795c9b2@arm.com> (raw)
In-Reply-To: <1465368899-7127-1-git-send-email-anjiandi@codeaurora.org>
Hello Jiandi,
On 08/06/2016 07:54, Jiandi An wrote:
> As the number of CPUs supported on the system grows, number of
> GIC redistributors and mmio handlers increase. We need to increase
> MAX_RDIST_COUNT and MAX_IO_HANDLER which makes size of struct domain
> bigger than one page.
With this change, the memory footprint of a domain will increase by 4KB
even if they don't use GICv3.
What is the size of the domain structure with your patch?
I would much prefer to allocate separate memory for the vGIC
redistributors if it takes too much space.
>
> Remove the BUILD_BUG_ON check for if size of struct domain is greater
> than PAGE_SIZE. And allocate xenheap pages according to the order of
> the size of struct domain.
>
> Signed-off-by: Jiandi An <anjiandi@codeaurora.org>
> ---
> xen/arch/arm/domain.c | 5 +++--
> xen/include/asm-arm/gic.h | 2 +-
> xen/include/asm-arm/mmio.h | 2 +-
> 3 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index 1365b4a..7f69236 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -438,8 +438,9 @@ void startup_cpu_idle_loop(void)
> struct domain *alloc_domain_struct(void)
> {
> struct domain *d;
> - BUILD_BUG_ON(sizeof(*d) > PAGE_SIZE);
> - d = alloc_xenheap_pages(0, 0);
> + unsigned int order = get_order_from_bytes(sizeof(*d));
> +
> + d = alloc_xenheap_pages(order, 0);
> if ( d == NULL )
> return NULL;
>
> diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
> index cd97bb2..8165de6 100644
> --- a/xen/include/asm-arm/gic.h
> +++ b/xen/include/asm-arm/gic.h
> @@ -20,7 +20,7 @@
>
> #define NR_GIC_LOCAL_IRQS NR_LOCAL_IRQS
> #define NR_GIC_SGI 16
> -#define MAX_RDIST_COUNT 4
> +#define MAX_RDIST_COUNT 64
How many re-distributor regions does your platform have?
>
> #define GICD_CTLR (0x000)
> #define GICD_TYPER (0x004)
> diff --git a/xen/include/asm-arm/mmio.h b/xen/include/asm-arm/mmio.h
> index da1cc2e..798d373 100644
> --- a/xen/include/asm-arm/mmio.h
> +++ b/xen/include/asm-arm/mmio.h
> @@ -23,7 +23,7 @@
> #include <asm/processor.h>
> #include <asm/regs.h>
>
> -#define MAX_IO_HANDLER 16
> +#define MAX_IO_HANDLER 32
The vGICv3 driver is allocating one I/O handler per redistributor
region. So if you bump MAX_RDIST_COUNT to 64, you at least need to bump
MAX_IO_HANDLER to 80.
However, I am bit concerned of the performance impact in long-term
because the lookup is linear.
Regards,
--
Julien Grall
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next prev parent reply other threads:[~2016-06-08 9:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-08 6:54 [PATCH] arm/domain: allocate pages according to the order of struct domain size Jiandi An
2016-06-08 9:26 ` Julien Grall [this message]
2016-06-09 0:09 ` Jiandi An
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