From: David Laight <David.Laight@ACULAB.COM>
To: 'Eric Dumazet' <eric.dumazet@gmail.com>,
Davide Caratti <dcaratti@redhat.com>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S. Miller" <davem@davemloft.net>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: RE: [PATCH net-next 2/2] net/sched: act_police: don't use spinlock in the data path
Date: Fri, 16 Nov 2018 14:41:45 +0000 [thread overview]
Message-ID: <a3ed82c1679e4bb5a8ab4233df38a03c@AcuMS.aculab.com> (raw)
In-Reply-To: <7ba53062-de84-a8f1-14dc-3c49a2480925@gmail.com>
From: Eric Dumazet
> Sent: 16 November 2018 14:35
...
> I suggest to use a single cache line with a dedicated spinlock and these three s64
>
> spinlock_t tcfp_lock ____cacheline_aligned_in_smp;
> s64 ...
> s64 ...
> s64 ...
Doesn't this do something really stupid when cache lines are big.
If the spinlock is 8 bytes you never want more than 32 byte alignment.
If cache lines are 256 bytes you don't even need that.
Also ISTR that the kmalloc() only guarantees 8 byte alignment on x86_64.
So aligning structure members to larger offsets is rather pointless.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2018-11-17 0:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-13 17:29 [PATCH net-next 0/2] net/sched: act_police: lockless data path Davide Caratti
2018-09-13 17:29 ` [PATCH net-next 1/2] net/sched: act_police: use per-cpu counters Davide Caratti
2018-09-13 17:29 ` [PATCH net-next 2/2] net/sched: act_police: don't use spinlock in the data path Davide Caratti
2018-11-15 6:46 ` Eric Dumazet
2018-11-15 11:43 ` Davide Caratti
2018-11-15 13:53 ` Eric Dumazet
2018-11-16 11:28 ` Davide Caratti
2018-11-16 14:34 ` Eric Dumazet
2018-11-16 14:39 ` Eric Dumazet
2018-11-16 14:41 ` David Laight [this message]
2018-11-16 14:55 ` Eric Dumazet
2018-09-16 22:32 ` [PATCH net-next 0/2] net/sched: act_police: lockless " David Miller
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