netdev - Re: [PATCH net-next] tcp: force a PSH flag on TSO packets

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Message-Id: <20190919.143252.1698401511955783402.davem@davemloft.net>
Date:   Thu, 19 Sep 2019 14:32:52 +0200 (CEST)
From:   David Miller <davem@...emloft.net>
To:     gerlitz.or@...il.com
Cc:     edumazet@...gle.com, netdev@...r.kernel.org,
        eric.dumazet@...il.com, soheil@...gle.com, ncardwell@...gle.com,
        ycheng@...gle.com, daniel@...earbox.net, tariqt@...lanox.com
Subject: Re: [PATCH net-next] tcp: force a PSH flag on TSO packets

From: Or Gerlitz <gerlitz.or@...il.com>
Date: Thu, 19 Sep 2019 15:17:54 +0300

> On Wed, Sep 11, 2019 at 12:54 AM Eric Dumazet <edumazet@...gle.com> wrote:
>> When tcp sends a TSO packet, adding a PSH flag on it
>> reduces the sojourn time of GRO packet in GRO receivers.
>>
>> This is particularly the case under pressure, since RX queues
>> receive packets for many concurrent flows.
>>
>> A sender can give a hint to GRO engines when it is
>> appropriate to flush a super-packet, especially when pacing
> 
> Hi Eric,
> 
> Is this correct that we add here the push flag for the tcp header template
> from which all the tcp headers for SW GSO packets will be generated?
> 
> Wouldn't that cause a too early flush on GRO engines at the receiver side?

I thought segmentation offload mechanism are not supposed to propagate
the PSH to all of the packets.