Received-SPF: pass (google.com: domain of linux-kernel+bounces-144601-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Precedence: bulk
Message-ID: <fbf1771d-d97c-488b-96ee-422d64016615@yandex-team.ru>
Date: Mon, 15 Apr 2024 09:36:51 +0300
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] kvm_host: bump KVM_MAX_IRQ_ROUTE to 128k
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, yc-core@yandex-team.ru
References: <20240321082442.195631-1-d-tatianin@yandex-team.ru>
Content-Language: en-US
From: Daniil Tatianin <d-tatianin@yandex-team.ru>
In-Reply-To: <20240321082442.195631-1-d-tatianin@yandex-team.ru>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

ping :)

On 3/21/24 11:24 AM, Daniil Tatianin wrote:
> We would like to be able to create large VMs (up to 224 vCPUs atm) with
> up to 128 virtio-net cards, where each card needs a TX+RX queue per vCPU
> for optimal performance (as well as config & control interrupts per
> card). Adding in extra virtio-blk controllers with a queue per vCPU (up
> to 192 disks) yields a total of about ~100k IRQ routes, rounded up to
> 128k for extra headroom and flexibility.
>
> The current limit of 4096 was set in 2018 and is too low for modern
> demands. It also seems to be there for no good reason as routes are
> allocated lazily by the kernel anyway (depending on the largest GSI
> requested by the VM).
>
> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
> ---
>   include/linux/kvm_host.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 48f31dcd318a..10a141add2a8 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2093,7 +2093,7 @@ static inline bool mmu_invalidate_retry_gfn_unsafe(struct kvm *kvm,
>   
>   #ifdef CONFIG_HAVE_KVM_IRQ_ROUTING
>   
> -#define KVM_MAX_IRQ_ROUTES 4096 /* might need extension/rework in the future */
> +#define KVM_MAX_IRQ_ROUTES 131072 /* might need extension/rework in the future */
>   
>   bool kvm_arch_can_set_irq_routing(struct kvm *kvm);
>   int kvm_set_irq_routing(struct kvm *kvm,