linux-kernel - Re: [PATCH] iomap: add allocation cache for iomap

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Message-ID: <aSA9VTO8vDPYZxNx@infradead.org>
Date: Fri, 21 Nov 2025 02:22:13 -0800
From: Christoph Hellwig <hch@...radead.org>
To: guzebing <guzebing1612@...il.com>
Cc: brauner@...nel.org, djwong@...nel.org, linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	guzebing <guzebing@...edance.com>,
	Fengnan Chang <changfengnan@...edance.com>
Subject: Re: [PATCH] iomap: add allocation cache for iomap_dio

On Fri, Nov 21, 2025 at 05:00:52PM +0800, guzebing wrote:
> From: guzebing <guzebing@...edance.com>
> 
> As implemented by the bio structure, we do the same thing on the
> iomap-dio structure. Add a per-cpu cache for iomap_dio allocations,
> enabling us to quickly recycle them instead of going through the slab
> allocator.
> 
> By making such changes, we can reduce memory allocation on the direct
> IO path, so that direct IO will not block due to insufficient system
> memory. In addition, for direct IO, the read performance of io_uring
> is improved by about 2.6%.

Have you checked how much of that you'd get by using a dedicated
slab cache that should also do per-cpu allocations?  Note that even
if we had a dedicated per-cpu cache we'd probably still want that.

Also any chance you could factor this into common code?