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Wed, 31 Jan 2024 02:53:45 -0500 X-MC-Unique: KHEcACATNOCZmihN0j5VXg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2346A86E91F; Wed, 31 Jan 2024 07:53:45 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0A15D2166B31; Wed, 31 Jan 2024 07:53:41 +0000 (UTC) From: Florian Weimer To: Yang Shi Cc: oliver.sang@intel.com, riel@surriel.com, fengwei.yin@intel.com, willy@infradead.org, cl@linux.com, ying.huang@intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 2/2] mm: mmap: map MAP_STACK to VM_NOHUGEPAGE References: <20231221065943.2803551-1-shy828301@gmail.com> <20231221065943.2803551-2-shy828301@gmail.com> Date: Wed, 31 Jan 2024 08:53:40 +0100 In-Reply-To: <20231221065943.2803551-2-shy828301@gmail.com> (Yang Shi's message of "Wed, 20 Dec 2023 22:59:43 -0800") Message-ID: <878r46ym4b.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-Rspamd-Queue-Id: 64D8BA000C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 877z44y5ay7dcn8wa9e1dqkt5x3yiztz X-HE-Tag: 1706687632-447350 X-HE-Meta: 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 evlYtynU S99TIgh9rXfLE9nPvRWEahFzqtAZ+8DjU4tD7k7p2B6YmR7Ynv3JBrTFH1g+iEl6eu5PFzYYPtd1d8J7YkAimPVs+KXfW8bXrkZwExJG2RPXsrlEutg810s9pxRK46G134u6CPr53+D0736KWAzCysvr7SYlS6SiZHcON3Ew/pS7fvuLFIEdZ25xMFG1X3hvevN6A76lYBh6/jdeZutXkh8bXK+Nwkh7uqSM0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: * Yang Shi: > From: Yang Shi > > The commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP > boundaries") incured regression for stress-ng pthread benchmark [1]. > It is because THP get allocated to pthread's stack area much more possible > than before. Pthread's stack area is allocated by mmap without VM_GROWSDOWN > or VM_GROWSUP flag, so kernel can't tell whether it is a stack area or not. > > The MAP_STACK flag is used to mark the stack area, but it is a no-op on > Linux. Mapping MAP_STACK to VM_NOHUGEPAGE to prevent from allocating > THP for such stack area. Doesn't this introduce a regression in the other direction, where workloads expect to use a hugepage TLB entry for the stack? It's seems an odd approach to fixing the stress-ng regression. Isn't it very much coding to the benchmark? Thanks, Florian