Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Angus Chen <angus.chen@jaguarmicro.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ming Lei <ming.lei@redhat.com>,
        Jason Wang <jasowang@redhat.com>
Subject: RE: IRQ affinity problem from virtio_blk
In-Reply-To: <TY2PR06MB34248DB15CBBDA7624DAFAE185079@TY2PR06MB3424.apcprd06.prod.outlook.com>
References: <TY2PR06MB3424CB11DB57CA1FAA16F10D85049@TY2PR06MB3424.apcprd06.prod.outlook.com>
 <87v8nfrhbw.ffs@tglx> <20221115174152-mutt-send-email-mst@kernel.org>
 <87sfijrf9o.ffs@tglx> <87o7t7rec7.ffs@tglx>
 <TY2PR06MB34248DB15CBBDA7624DAFAE185079@TY2PR06MB3424.apcprd06.prod.outlook.com>
Date:   Wed, 16 Nov 2022 11:54:35 +0100
Message-ID: <87iljfqidw.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, Nov 16 2022 at 00:46, Angus Chen wrote:
>> On Wed, Nov 16 2022 at 00:04, Thomas Gleixner wrote:
>> >>> But then it also has another 79 vectors put aside for the other queues,
> en,it not the truth,in fact ,I just has one queue for one virtio_blk.

Which does not matter. See my reply to Michael. It's ONE vector per CPU
and block device.

> Nov 14 11:48:45 localhost kernel: virtio_blk virtio181: 1/0/0 default/read/poll queues
> Nov 14 11:48:45 localhost kernel: virtio_blk virtio181: [vdpr] 20480 512-byte logical blocks (10.5 MB/10.0 MiB)
> Nov 14 11:48:46 localhost kernel: virtio-pci 0000:37:16.4: enabling device (0000 -> 0002)
> Nov 14 11:48:46 localhost kernel: virtio-pci 0000:37:16.4: virtio_pci: leaving for legacy driver
> Nov 14 11:48:46 localhost kernel: virtio_blk virtio182: 1/0/0 default/read/poll queues---------the virtio182 means index 182.
> Nov 14 11:48:46 localhost kernel: vp_find_vqs_msix return err=-28-----------------------------the first time we get 'no space' error from irq subsystem. 

That's close to 200 virtio devices and the vector space is exhausted.
Works as expected.

Interrupt vectors are a limited resource on x86 and not only on x86. Not
any different from any other resource.

Thanks,

        tglx