From: Rick Jones <rick.jones2@hpe.com>
To: Michael Richardson <mcr@sandelman.ca>,
netdev@vger.kernel.org, linux-wpan@vger.kernel.org
Cc: Alexander Aring <aar@pengutronix.de>
Subject: Re: drop all fragments inside tx queue if one gets dropped
Date: Wed, 20 Apr 2016 13:45:50 -0700 [thread overview]
Message-ID: <5717EA7E.1020606@hpe.com> (raw)
In-Reply-To: <11312.1461183334@obiwan.sandelman.ca>
For the "everything old is new again" files, back in the 1990s, it was
noticed that on the likes of a netperf UDP_STREAM test on HP-UX, with
fragmentation taking place, it was possible to consume 100% of the link
bandwidth and have 0% effective throughput because the transmit queue
was kept full with IP datagram fragments which could not possibly be
reassembled (*) because one or more of the fragments of a datagram were
dropped because the transmit queue was full.
HP-UX implemented "packet trains" where all the fragments of a
fragmented datagram were presented to the driver, which then either
queued them all, or none of them.
I don't recall seeing similar poor behaviour in Linux; I would have
assumed that the intra-stack flow-control "took care" of it. Perhaps
there is something specific to wpan which precludes that?
happy benchmarking,
rick jones
next prev parent reply other threads:[~2016-04-20 20:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-20 9:52 drop all fragments inside tx queue if one gets dropped Alexander Aring
2016-04-20 20:15 ` Michael Richardson
2016-04-20 20:45 ` Rick Jones [this message]
2016-04-21 17:48 ` Michael Richardson
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