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Wed, 04 Nov 2026 21:23:48 -0800 (PST) Received: from google.com ([2a00:79e0:2031:6:37bc:b763:7ec7:65b4]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b245c463e9sm13218160c88.14.2026.11.04.21.23.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 21:23:47 -0800 (PST) Date: Thu, 5 Nov 2026 14:23:43 +0900 From: Sergey Senozhatsky To: Jenhao Chen Cc: Minchan Kim , Sergey Senozhatsky , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, minchan@google.com, liumartin@google.com, benwei@google.com Subject: Re: [PATCH] mm/zsmalloc: inline obj_malloc() and obj_free() Message-ID: References: <20261030121700.260975-1-jenhaochen@google.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261030121700.260975-1-jenhaochen@google.com> On (26/10/30 12:17), Jenhao Chen wrote: > In zs_malloc(), the fast path (if (likely(zspage))) allocates from an > existing zspage via obj_malloc(), while the slow path allocates a new > zspage via alloc_zspage(). > > Because obj_malloc() has three call sites across zs_malloc() and > migrate_zspage(), Clang at -O2 leaves obj_malloc() out-of-line, adding a > function call on every fast-path allocation. Conversely, because the > 362-instruction slow-path alloc_zspage() is static with a single caller, > single-caller inlining under CONFIG_AUTOFDO_CLANG (e.g. with > CONFIG_ZSMALLOC=m) inlines alloc_zspage() into zs_malloc(), growing it > from 254 to 691 instructions. > > Mark obj_malloc() and obj_free() __always_inline and mark alloc_zspage() > noinline to keep the fast path inline and the slow-path page allocation > out-of-line. I suppose there is performance benefit? I guess I don't mind in principle, one thing to note is that this conflicts with [1]. [1] https://lore.kernel.org/linux-kernel/20261105044752.1997895-1-senozhatsky@chromium.org