linux-kernel - Re: [PATCH v2 1/3] mm: vmalloc: Let user to control huge vmalloc default behavior

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Date:   Wed, 19 Jan 2022 13:22:04 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 1/3] mm: vmalloc: Let user to control huge vmalloc
 default behavior

On Wed, Jan 19, 2022 at 08:57:58PM +0800, Kefeng Wang wrote:
> Only parts of our products wants this feature,  we add some interfaces which
> only
> 
> alloc hugevmalloc for them, eg,
> vmap_hugepage/vmalloc_hugepage/remap_vmalloc_hugepage_range..
> 
> for our products, but it's not the choice of most products, also add
> nohugevmalloc
> 
> for most products is expensive, so this is the reason for adding the patch.
> 
> more config/cmdline are more flexible for test/products，

But why do only some products want it?  What goes wrong if all products
enable it?  Features should be auto-tuning, not relying on admins to
understand them.