linux-kernel - Re: [PATCH v2] mm/vmalloc: lock contention optimization under multi-threading

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Date: Tue, 20 Feb 2024 11:54:33 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: rulinhuang <rulin.huang@...el.com>
Cc: urezki@...il.com, colin.king@...el.com, hch@...radead.org,
 linux-kernel@...r.kernel.org, linux-mm@...ck.org, lstoakes@...il.com,
 tim.c.chen@...el.com, zhiguo.zhou@...el.com, wangyang.guo@...el.com,
 tianyou.li@...el.com
Subject: Re: [PATCH v2] mm/vmalloc: lock contention optimization under
 multi-threading

On Tue, 20 Feb 2024 04:05:21 -0500 rulinhuang <rulin.huang@...el.com> wrote:

> When allocating a new memory area where the mapping address range is
> known, it is observed that the vmap_area lock is acquired twice.
> The first acquisition occurs in the alloc_vmap_area() function when
> inserting the vm area into the vm mapping red-black tree. The second
> acquisition occurs in the setup_vmalloc_vm() function when updating the
> properties of the vm, such as flags and address, etc.
> Combine these two operations together in alloc_vmap_area(), which
> improves scalability when the vmap_area lock is contended. By doing so,
> the need to acquire the lock twice can also be eliminated.
> With the above change, tested on intel icelake platform(160 vcpu, kernel
> v6.7), a 6% performance improvement and a 7% reduction in overall
> spinlock hotspot are gained on
> stress-ng/pthread(https://github.com/ColinIanKing/stress-ng), which is
> the stress test of thread creations.

vmalloc.c has changed a lot lately.  Please can you work against
linux-next or against the mm-unstable branch of
//git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Thanks.