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[124.171.74.95]) by smtp.gmail.com with ESMTPSA id i4sm617438pjj.30.2022.01.17.18.53.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Jan 2022 18:53:01 -0800 (PST) Date: Tue, 18 Jan 2022 12:52:56 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 1/3] mm: vmalloc: Let user to control huge vmalloc default behavior To: Andrew Morton , Jonathan Corbet , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Kefeng Wang , x86@kernel.org References: <20211227145903.187152-1-wangkefeng.wang@huawei.com> <20211227145903.187152-2-wangkefeng.wang@huawei.com> In-Reply-To: <20211227145903.187152-2-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Message-Id: <1642473992.qrnqczjfna.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Matthew Wilcox , Catalin Marinas , Dave Hansen , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Paul Mackerras , Thomas Gleixner , Will Deacon Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Kefeng Wang's message of December 28, 2021 12:59 am: > Introduce HUGE_VMALLOC_DEFAULT_ENABLED and make it default y, this > let user to choose whether or not enable huge vmalloc mappings by > default. >=20 > Meanwhile, add new hugevmalloc=3Don/off parameter to enable or disable > this feature at boot time, nohugevmalloc is still supported and > equivalent to hugevmalloc=3Doff. Runtime options are bad enough, Kconfig and boot options are even worse. The 'nohugevmalloc' option mirrors 'nohugeiomap' and is not expected to ever be understood by an administrator unless a kernel developer is=20 working with them to hunt down a regression. IMO there should be no new options. You could switch it off for=20 CONFIG_BASE_SMALL perhaps, and otherwise just try to work on heuristics first. Bring in new options once it's proven they're needed. Aside from that, thanks for working on these ports, great work. Thanks, Nick