linux-kernel - Re: [PATCH v2 1/3] lib/list_batch: A simple list insertion/deletion batching facility

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Date:	Tue, 16 Feb 2016 20:37:33 -0500
From:	Waiman Long <waiman.long@....com>
To:	Dave Chinner <david@...morbit.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	<linux-fsdevel@...r.kernel.org>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH v2 1/3] lib/list_batch: A simple list insertion/deletion
 batching facility

On 02/06/2016 06:57 PM, Dave Chinner wrote:
> On Wed, Feb 03, 2016 at 06:11:56PM -0500, Waiman Long wrote:
>> On 01/31/2016 07:47 PM, Dave Chinner wrote:
>>> So at what point does simply replacing the list_head with a list_lru
>>> become more efficient than this batch processing (i.e.
>>> https://lkml.org/lkml/2015/3/10/660)?  The list_lru isn't a great
>>> fit for the inode list (doesn't need any of the special LRU/memcg
>>> stuff https://lkml.org/lkml/2015/3/16/261) but it will tell us if,
>>> like Ingo suggested, moving more towards a generic per-cpu list
>>> would provide better overall performance...
>> I will take a look at the list_lru patch to see if that help. As for
>> the per-cpu list, I tried that and it didn't quite work out.
> OK, see my last email as to why Andi's patch didn't change anything.
> The list_lru implementation has a list per node, a lock per node,
> and each item is placed on the list for the node it is physically
> allocated from. Hence for local workloads, the list/lock that is
> accessed for add/remove should be local to the node and hence should
> reduce cache line contention mostly to within a single node.
>
> Cheers,
>
> Dave.

I have just sent out a new patchset using per-cpu list with per-cpu 
locks. I used the per-cpu list as the changes will be simpler and easier 
to review. Please let me know your thought on that.

Thanks,
Longman