linux-kernel - Re: [PATCH 4/6] bpf: hash: convert per-hashtable lock into per-bucket bit spinlock

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Message-ID: <CACVXFVNgkvuhVKo2PMbh2LM4t-A+r+Q+VLVnLe6XRsbeWRoCjw@mail.gmail.com>
Date:	Sat, 26 Dec 2015 16:58:45 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Yang Shi <shy828301@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Network Development <netdev@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 4/6] bpf: hash: convert per-hashtable lock into per-bucket
 bit spinlock

On Fri, Dec 18, 2015 at 2:20 PM, Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> On Wed, Dec 16, 2015 at 02:58:08PM +0800, Ming Lei wrote:
>> On Wed, Dec 16, 2015 at 1:01 PM, Yang Shi <shy828301@...il.com> wrote:
>>
>> >
>> > I recalled Steven confirmed raw_spin_lock has the lockdep benefit too in the
>> > patch review for changing to raw lock.
>> >
>> > Please check this thread out
>> >  http://lists.openwall.net/netdev/2015/10/31/7
>>
>> OK, looks I was wrong about the lockdep benifit, :-(
>>
>> But for this lock, I think lockdep isn't such important, because it is the
>> intermost lock, and it can be used just for protecting the bucket list
>> and nothing else need to be covered.
>
> I still think that overhead of normal spinlock per bucket is acceptable.
> Makes the whole thing much easier to read.

OK, let's use per-bucket spinlock first.

--
Ming Lei
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