From: christophe leroy <christophe.leroy@c-s.fr>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: netdev <netdev@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>
Subject: Performance loss due to commit 37c3185 ([NET]: Added GSO toggle)
Date: Sat, 20 Jun 2015 11:55:03 +0200 [thread overview]
Message-ID: <55853877.9080000@c-s.fr> (raw)
Hello Herbert,
In commit "[NET]: Added GSO toggle"
37c3185a02d4b85fbe134bf5204535405dd2c957,
you force NETIF_F_HW_CSUM if GSO feature is selected.
By default, SW GSO is active as soon as a network board has NETIF_F_SG
feature.
This means that function sk_setup_caps() forces NETIF_F_HW_CSUM for any
board having NETIF_F_SG
For boards having no HW checksum capability, this results in performance
loss due to data copy being done in skb_do_copy_data_nocache() with
copy_from_user() then checksum being done later with csum_partial()
instead of getting both done at the same time using
csum_and_copy_from_user()
Is there a reason for forcing NETIF_F_HW_CSUM ?
Christophe
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next reply other threads:[~2015-06-20 10:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-20 9:55 christophe leroy [this message]
2015-06-25 14:37 ` Performance loss due to commit 37c3185 ([NET]: Added GSO toggle) Herbert Xu
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