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b=DRb5CgSXJVFnImbAzQqZCZCcwtgYQEw4dEf2oZNaSl8f9BldFWf3dqEu6szwChb7a Nl5F8NIFubdniAjqsqWVJhRW5m3pWMbxDyppBHio8HDffUahTY4TCSHoD9xm6S27ZM 0hBPUtWEy/jUbKGs+UwJhjZcL4ltxJ5FLwtjGubpsNXBgbAKawwB5COX83W1XPWbWQ YC7oRJ5fjQ55lHnd4cWc1DyTiMsDliCsbsnU2w/BJfNKAiPLoquK9yy5ijbhoVS2Ne xFkUxq/IL4vb7BA8NchKDxYMlC/X6Kmnu6R1bFLOxLEvwT/VHAwBNRfJsSG2hUv2Mn PoUAtfLKlLXzg== Date: Wed, 13 May 2026 01:23:16 -0700 From: Dennis Zhou To: Andrew Morton Cc: Hongling Zeng , dennis@kernel.org, tj@kernel.org, cl@gentwo.org, linux-mm@kvack.org, kernel@vger.kernel.org, zhongling0719@126.com Subject: Re: [PATCH RESEND v2] mm/percpu-internal.h: optimise pcpu_chunk struct to save memory Message-ID: References: <20260511070309.44044-1-zenghongling@kylinos.cn> <20260512150340.c8ae97f9299918a1f12f3e7d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512150340.c8ae97f9299918a1f12f3e7d@linux-foundation.org> X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 13D74C0002 X-Stat-Signature: yfnfd5z7wts3yphmgqutzndke7ic65rb X-HE-Tag: 1778660599-827967 X-HE-Meta: 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 Vb4mJPwa ci2n4J3xx7RFN1YpJWQvHullgySRhdTbOKNNQScreJfUJHoo6k/rwtlzrDHFDk41aQk8RHj/fJziiRAt92UN/Jh0TkfnKKauOIUdVT49fldF/TgqZr0ucCJvXmTkzP0Qul0X4EeLrKMXYdtcoYOspxFLPewOaWKLQ+mQJJlOYhwq5E6BXe/b2Yu7YqlCw9tWscYYTT+qtiIc7TZE5B458YqRGrnizhoUWuhGE/SzFFRHUWGicRefNt7fOjg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Andrew, On Tue, May 12, 2026 at 03:03:40PM -0700, Andrew Morton wrote: > On Mon, 11 May 2026 15:03:09 +0800 Hongling Zeng wrote: > > > Using pahole, we can see that there are some padding holes > > in the current pcpu_chunk structure,Adjusting the layout of pcpu_chunk > > can reduce these holes,decreasing its size from 192 bytes to 128 bytes > > and eliminating a wasted cache line. > > > > With allmodconfig (CONFIG_PERCPU_STATS + NEED_PCPUOBJ_EXT) > > Before: > > /* size: 256, cachelines: 4, members: 19 */ > > > > After: > > /* size: 192, cachelines: 3, members: 19 */ > > Thanks, I'll add this to mm.git for testing, but I'm not planning on > taking it further until Dennis has taken a look. > Sorry, I thought we took care of this one prior before. This is per chunk metadata, so it won't save much. That being said it doesn't hurt. Acked-by: Dennis Zhou I'm thinking about the other percpu series now. Thanks, Dennis