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Sat, 07 Mar 2026 06:42:18 -0800 (PST) From: Xie Yuanbin To: rppt@kernel.org, akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, david@kernel.org, justinstitt@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, llvm@lists.linux.dev, mhocko@suse.com, morbo@google.com, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, qq570070308@gmail.com, surenb@google.com, vbabka@kernel.org Subject: Re: [PATCH] mm: optimize once judgment with clang Date: Sat, 7 Mar 2026 22:41:35 +0800 Message-ID: <20260307144135.380683-1-qq570070308@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 453381C0007 X-Stat-Signature: 3ohe71t5enncosp64hichbxdnump9rkt X-Rspam-User: X-HE-Tag: 1772894540-403723 X-HE-Meta: U2FsdGVkX19sRNCy8V6oWsqkdzlFYU/9KvUQQKc/iVYkwaQjezSfosloazwh4/8ELdBDdqqtXkKzbX8ZejrYzSJ1l5bHC381daNBsSXWUPAc6gxgTNeQX8LkLt7kiIVJjHJh3Yn00PhLVFGd6TWbSdlzcDA69WrSfdnWeCxCB08T6lHVT5U2MTe5NP1OXXAWJzqNXiRPWPS233LlhWTqeuArvSi/TfeaAUzrSTK8fOrO8+lgAACvYhUjM3i8B6HpoyX8AJwMscnFnli2f4ju6yVq9KaSfHInWQPTWJLlbVrW8XQkP/A2iEQ80u6byDVZ7Y436842P5qrICnX+mQFFOWR7Qvb605YP0+Duep9zKOmMIoA3zvIa/rTF3Z2ldEAqdvioel+yo6WwagfeucZQwfz5iCtwZD4LK57GDyrFOVwPXw1dP9LyS2X7XgCq5S/WgLjj8PskAGrqiiTmuZiwAI2RW+7tQLPrV4MtzrUOdNdMUryYsUedWiI22t9BYaJ5qgI+z/JO2K0OVC0TG7Rvt8vugyI280tbe9ujFOBX6edcZOPcJGFb4NCc9RDxqZkf1sr+RDkPltCRci11Z0et8wTrxCJC+2yE69r5PurubnuEHSobF0mhqbpvrKOUQ+OsRLJVbBMUsx4eIu1B0eTPyErDIYMfWrHqDA65CfmATSZjMXpsKPlZrErsql4z+23SxyA+jmdNjwXnJs2kh18LEj/1A9J9q7vxy7o1COk2B/MX9jS4CPi5eDnbJfX1eTUcE1LDphR8dikWCq6rNyIOCK4On81jiMqGFZ8UDvdIy6AgJvt0VkFA855HG+H5wP4gMrQ3PPXd+vht7sjGJHHMJZNUEGutfMWeuWYagpiDdgEonih8uurrKC3rQMrvdV3PnsaZpxYmwPsB5i1XbNGYpYmv/hDv1lKVGL1yOrpOfqUeb3hUzBMdPbGu/ESwYNAMW0BCUOyaS55Y7GKW/C qYd3zB5k BkJJLYIv0xPnMWw6Bv/4iPnjes5oGnCVVgqelqouPIWmy5Ucm6DcmRkobdALRKOVIyU5X0tejPinth3UQQfu3L80n+6tzl/1f/rhsX+4g9+gVTdaY0mCNYzXrKA4vumtGzmHB4E8/Camp+KumbRve9iuEtp7Q9TRT4vckJLWxphGSucJzuijIFoZZx0B1FAl+/3tY5Bn/+RyCOkWNIdGNrtyE5gT4hLvFG7qbKKjkolDIUTjXACo+ipnsk8lnoa3Z3pBZpVlGmxfQMDu4mB57QxExUGfud6ZUFE5KFShnx5AF+vVE8c+1Z2kUkZyUlf0KB0z8RB+K4iY3Cw98TSbl7KiAWMIadwC727Z0cvNowsc14lBOOAk6AiZXYLUc71htZhnENrD0uV3HqpQWmidR5ThvMFw1i/dEpikFpRchLwHDD82ybf8QpuF7nUSVst00boMBurxmGAH+Ta/pnFJVw6KZJA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 7 Mar 2026 10:12:18 +0200, Mike Rapoport wrote: > On Sat, Mar 07, 2026 at 02:54:04PM +0800, Xie Yuanbin wrote: >> commit 242b872239f6a7deacbc ("include/linux/once_lite.h: fix judgment in >> WARN_ONCE with clang") helps optimize performance and size under the >> clang compiler, but the modification is not complete. > > How much does it actually optimize for size? Basing on commit a0ae2a256046c0c5d377 ("Add linux-next specific files for 20260306"), compiler "Debian clang version 21.1.8 (5)", arm64 default defconfig, and setting CONFIG_CC_OPTIMIZE_FOR_SIZE=y, the size result is: | | size | | -| -| | Image.gz | 14256146 | | size of ".text" section in vmlinex | 17035264 | Basing on above, revert the commit 242b872239f6a7deacbc ("include/linux/once_lite.h: fix judgment in WARN_ONCE with clang"), and build again: | | size | | -| -| | Image.gz | 14258152(+2006) | | size of ".text" section in vmlinex | 17039360(+4096) | > Note that performance is really not critical here because we are already > dealing with slow path of debug code. It seems that WARN_ON_ONCE_GFP() is not affected by in CONFIG_DEBUG_VM, and it is used in __alloc_frozen_pages_noprof(), which seems to be a hot path.