netdev - Re: [PATCH net v4] atl1c: move tx cleanup processing out of interrupt

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Date:   Tue, 06 Apr 2021 16:44:46 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     gatis@...rotik.com
Cc:     chris.snook@...il.com, kuba@...nel.org, hkallweit1@...il.com,
        jesse.brandeburg@...el.com, dchickles@...vell.com,
        tully@...rotik.com, eric.dumazet@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v4] atl1c: move tx cleanup processing out of
 interrupt

From: Gatis Peisenieks <gatis@...rotik.com>
Date: Tue, 06 Apr 2021 17:49:32 +0300

> Tx queue cleanup happens in interrupt handler on same core as rx queue
> processing. Both can take considerable amount of processing in high
> packet-per-second scenarios.
> 
> Sending big amounts of packets can stall the rx processing which is
> unfair
> and also can lead to out-of-memory condition since __dev_kfree_skb_irq
> queues the skbs for later kfree in softirq which is not allowed to
> happen
> with heavy load in interrupt handler.
> 
> This puts tx cleanup in its own napi and enables threaded napi to
> allow
> the rx/tx queue processing to happen on different cores. Also as the
> first
> in-driver user of dev_set_threaded API, need to add EXPORT_SYMBOL for
> it.
> 
> The ability to sustain equal amounts of tx/rx traffic increased:
> from 280Kpps to 1130Kpps on Threadripper 3960X with upcoming
> Mikrotik 10/25G NIC,
> from 520Kpps to 850Kpps on Intel i3-3320 with Mikrotik RB44Ge adapter.
> 
> Signed-off-by: Gatis Peisenieks <gatis@...rotik.com>
> ---
> changes since v3:
> 	- made scripts/checkpatch.pl happy (commit message line wrap +
> 	  missing comment on spinlock)
> 	- moved the new intr_mask_lock to be besides the intr_mask it
> 	  protects so they are more likely to be on same cacheline
> changes since v2:
> 	- addressed comments from Eric Dumazet
> 	- added EXPORT_SYMBOL for dev_set_threaded
> 
> Sorry for reposting, noticed that scripts/checkpatch.pl was not happy.

This does not apply to 'net',  did you mean 'net-next'?  If so, please indicate this clearly in
the Subject line as per convention.

Thank you.