linux-kernel - Re: [PATCH v3 07/11] mm: vmalloc: Offload free_vmap_area

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Message-ID: <ZZ+umGZ2NFQN/KuW@dread.disaster.area>
Date: Thu, 11 Jan 2024 20:02:16 +1100
From: Dave Chinner <david@...morbit.com>
To: "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Matthew Wilcox <willy@...radead.org>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>
Subject: Re: [PATCH v3 07/11] mm: vmalloc: Offload free_vmap_area_lock lock

On Tue, Jan 02, 2024 at 07:46:29PM +0100, Uladzislau Rezki (Sony) wrote:
> Concurrent access to a global vmap space is a bottle-neck.
> We can simulate a high contention by running a vmalloc test
> suite.
> 
> To address it, introduce an effective vmap node logic. Each
> node behaves as independent entity. When a node is accessed
> it serves a request directly(if possible) from its pool.
> 
> This model has a size based pool for requests, i.e. pools are
> serialized and populated based on object size and real demand.
> A maximum object size that pool can handle is set to 256 pages.
> 
> This technique reduces a pressure on the global vmap lock.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Why not use a llist for this? That gets rid of the need for a
new pool_lock altogether...

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com