linux-kernel - Re: Latency spikes on V6.15.1 Preempt RT and maybe related to intel? IGB

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Message-ID: <20250617092814.vqKdu23w@linutronix.de>
Date: Tue, 17 Jun 2025 11:28:14 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Marc Strämke <marc.straemke@...ropuls.de>
Cc: linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: Latency spikes on V6.15.1 Preempt RT and maybe related to intel?
 IGB

On 2025-06-14 10:52:36 [+0200], Marc Strämke wrote:
>               ip-4931    [001] b...3   700.149995: igb_update_mc_addr_list <-igb_set_rx_mode
>               ip-4931    [001] Dn..3   700.150795: irq_disable: caller=irqentry_enter+0x2a/0x60 parent=0x0

Between those two functions you have 800us delay. Interrupts are not
disabled so the CPU stalls. As explained earlier, I expect the read on
the bus flushes the writes causing the spike.

Sebastian