From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>,
'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 06:55:34 -0800 [thread overview]
Message-ID: <2bfef133-8dbf-728c-f815-929291b4c68e@gmail.com> (raw)
In-Reply-To: <a3ed82c1679e4bb5a8ab4233df38a03c@AcuMS.aculab.com>
On 11/16/2018 06:41 AM, David Laight wrote:
> 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.
We do want that, even if cache lines are 256 bytes, thank you.
>
> Also ISTR that the kmalloc() only guarantees 8 byte alignment on x86_64.
> So aligning structure members to larger offsets is rather pointless.
No it is not, we use these hints all the time.
Just double check and report a bug to mm teams if you disagree.
Please do not send feedback if you are not sure.
next prev parent reply other threads:[~2018-11-17 1:08 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
2018-11-16 14:55 ` Eric Dumazet [this message]
2018-09-16 22:32 ` [PATCH net-next 0/2] net/sched: act_police: lockless " David Miller
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