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

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Message-ID: <93db576e-9a62-ee98-5af2-a62f8386212c@huawei.com>
Date:   Wed, 19 Jan 2022 21:44:20 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
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 2022/1/19 21:22, Matthew Wilcox wrote:
> 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.

Because this feature will use more memory for vmalloc/vmap, that's why 
we add some explicit
interfaces as said above in our kernel to control the user.