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b=T4o3pel74ki5lb+QT8HOdIrQtEGla5kb/L2PBSrfkRLDOfF+w347Hr/V4Z1xvGdzy ykVuyD1VUPxpezth7FPAgd5mZpBtO2uSeFlsmhGl4vDgv3hWHgKh7UHZ+arSwpfIrf CjzH2AzXfYzJGRS3FEkZ9RTVwqZAYmJ7+8rWVTcQ= Date: Tue, 12 May 2026 15:03:40 -0700 From: Andrew Morton To: Hongling Zeng Cc: 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: <20260512150340.c8ae97f9299918a1f12f3e7d@linux-foundation.org> In-Reply-To: <20260511070309.44044-1-zenghongling@kylinos.cn> References: <20260511070309.44044-1-zenghongling@kylinos.cn> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DC0608000F X-Rspam-User: X-Stat-Signature: g9us3anuppft1wuja7qrgiuxangtwo5r X-HE-Tag: 1778623421-831078 X-HE-Meta: U2FsdGVkX19I1ILkZRwp20RsKbnZMuvezTUjurZ0TCqT/WvW3s+2oPM34PqdRf7caQW02k1NNlYoKp7oljAnIcvJ3CCeCWx7Vfb23aFFDVh+JMeSymyngoC9nCb1R37H8oNJDPCUI2QRt+2L1gn8geJSKEaCaE3dG5ZaBKns/Y+WRbZ9NebrGshDzSm4qphYAU16tQg8SICzqhXGCYvjoQPceZdUD6bml93g2O8A94q0xBX1vWk+PNXtTwa9Dx694BXwTRNKOFbhuQp8L4jRHP6/iMCazumjMt5hgMgMB1mQPyXjRmBi7fHeZbOyr4xHVVQrSMNk1hCM8w2bOKHtgFdJ8vEWrT5MN83l+ZdI/YZrvaYfOc5yYAsmzpszR9WBG+xgA9D6AZSowNa5SvenwA/BoDRaMIpeNeTkf8DvZ/44SheBT+8r3ibFPrWsXMER9bGAqlU4ROTuMVLUDNXu6RVjvM1xBBN280KRNAkUyF9ABgHE9av+0GnIprr9TUwUBu2Q0tdtTvMHgpfBAOpx7cJY5+PcO3vEpBGBXDBIPWIhpvegyXGM1+fNmtoxu2qOGRzV7HHCd7bNMbAGtYqCGn2aA67GXY5hMuY/e5cHY1utKpKRFRvNx6ETkxVj/XgQ0sGGS3qHmA31xmjuSOCuUF3a/RCxr+x0a0NHbQ4UqlMjH1najMButTJQ7oOqHzYksnPVyWPr0yCk6Sk8OXwCtoy7EPZDltxusxS7efu9MQRhi6EuFSyt7q6TSGrJpy2AuEcxx6/kOzZvakeLRcbTqU5RpSrPJ72otTL39RXEmpxHFAcfTK7riRmy2ogGBqnlqJES/JLLP2wCKnC6nkAJNi8z9cJJbQzLr4hyALyWhdYCsKBP0C8kI4Uzq0OZsVRTf31w4WPbGUliOpChxXxZf2GslK4wmHWplM3XCyA+AZJGs9FMJXV/F6C0YVTq6hS0KjikGi/14tzOi3xCSNq 5d7sDAyE RZ4ka6sDyIDU0UMMlCnQiWU0ePtjNpx+jnkREKMlkX4s4EXiYlS/n6CR/C17JfUL+JQCfCQaiX5w3mn+nvUmPmKByrRkAe4001kDN8ax5undEzsiai9YN7rAYQhANIRBpxTAxuP+68ypUETNWew2CLG7GJrhp+Tfq7oI+ORkGG5658KioscsVcey/HGogo8OLlw4opp74PgRYCPr5zAvBsH0X7DnSKAP/t0DWaZYLxKp/76fix3EpcS8PSkM1GvmB2X6TCOZqZYY8DAzZKLe0FyXHNveWUrJOPCHCX5xB7trzlXWDO+qz/O/9zURZukkQU3dAAmv1tWSm0og= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.