From: Jakub Kicinski <kuba@kernel•org>
To: Haiyang Zhang <haiyangz@microsoft•com>
Cc: Erni Sri Satya Vennela <ernis@linux•microsoft.com>,
Erni Sri Satya Vennela <ernis@microsoft•com>,
KY Srinivasan <kys@microsoft•com>,
"wei.liu@kernel•org" <wei.liu@kernel•org>,
Dexuan Cui <decui@microsoft•com>,
"davem@davemloft•net" <davem@davemloft•net>,
"edumazet@google•com" <edumazet@google•com>,
"pabeni@redhat•com" <pabeni@redhat•com>,
"linux-hyperv@vger•kernel.org" <linux-hyperv@vger•kernel.org>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
"linux-kernel@vger•kernel.org" <linux-kernel@vger•kernel.org>
Subject: Re: [PATCH v2] net: netvsc: Update default VMBus channels
Date: Fri, 16 Aug 2024 08:52:41 -0700 [thread overview]
Message-ID: <20240816085241.326978a6@kernel.org> (raw)
In-Reply-To: <CH2PPF910B3338DB4798D086CB50600C2FBCA802@CH2PPF910B3338D.namprd21.prod.outlook.com>
On Thu, 15 Aug 2024 19:23:50 +0000 Haiyang Zhang wrote:
> Your suggestion on netif_get_num_default_rss_queues() is not ignored.
> We discussed internally on the formula we used for the num_chn, and
> chose a similar formula for higher number of vCPUs as in
> netif_get_num_default_rss_queues().
> For lower number of vCPUs, we use the same default as Windows guests,
> because we don't want any potential regression.
Ideally you'd just use netif_get_num_default_rss_queues()
but the code is close enough to that, and I don't have enough
experience with the question of online CPUs vs physical CPUs.
I would definitely advise you to try this on real workloads.
While "iperf" looks great with a lot of rings, real workloads
suffer measurably from having more channels eating up memory
and generating interrupts.
But if you're confident with the online_cpus() / 2, that's fine.
You may be better off coding it up using max:
dev_info->num_chn = max(DIV_ROUND_UP(num_online_cpus(), 2),
VRSS_CHANNEL_DEFAULT);
next prev parent reply other threads:[~2024-08-16 15:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-14 16:59 [PATCH v2] net: netvsc: Update default VMBus channels Erni Sri Satya Vennela
2024-08-14 18:23 ` Haiyang Zhang
2024-08-14 23:57 ` Michael Kelley
2024-08-15 14:50 ` Haiyang Zhang
2024-08-15 17:25 ` Michael Kelley
2024-08-15 16:08 ` Jakub Kicinski
2024-08-15 19:23 ` Haiyang Zhang
2024-08-16 15:52 ` Jakub Kicinski [this message]
2024-08-20 19:12 ` Erni Sri Satya Vennela
2024-08-16 14:48 ` Erni Sri Satya Vennela
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