Received-SPF: pass (google.com: domain of linux-kernel+bounces-23819-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: Uladzislau Rezki <urezki@gmail.com>
Date: Thu, 11 Jan 2024 16:54:48 +0100
To: Dave Chinner <david@fromorbit.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>, linux-mm@kvack.org,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>, Baoquan He <bhe@redhat.com>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Christoph Hellwig <hch@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Subject: Re: [PATCH v3 07/11] mm: vmalloc: Offload free_vmap_area_lock lock
Message-ID: <ZaAPSJHGsmG_oHAU@pc638.lan>
References: <20240102184633.748113-1-urezki@gmail.com>
 <20240102184633.748113-8-urezki@gmail.com>
 <ZZ+umGZ2NFQN/KuW@dread.disaster.area>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <ZZ+umGZ2NFQN/KuW@dread.disaster.area>

On Thu, Jan 11, 2024 at 08:02:16PM +1100, Dave Chinner wrote:
> 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@gmail.com>
> 
> Why not use a llist for this? That gets rid of the need for a
> new pool_lock altogether...
> 
Initially i used the llist. I have changed it because i keep track
of objects per a pool to decay it later. I do not find these locks
as contented one therefore i did not think much.

Anyway, i will have a look at this to see if llist is easy to go with
or not. If so i will send out a separate patch.

Thanks!

--
Uladzislau Rezki