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Mon, 29 Mar 2021 10:25:30 +0000 (GMT) Date: Mon, 29 Mar 2021 19:12:55 +0900 From: Hyunsoon Kim To: Leon Romanovsky Cc: Andrew Morton , dseok.yi@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: add ___GFP_NOINIT flag which disables zeroing on alloc Message-ID: <20210329101255.GA144155@ubuntu> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupjk+LIzCtJLcpLzFFi42LZdljTTFd6dWKCQU+3kMWc9WvYLK5M+8No MeXXUmaLy7vmsFncW/Of1YHVY9OqTjaPTZ8msXucmPGbxaNvyypGj8+b5AJYo3JsMlITU1KL FFLzkvNTMvPSbZW8g+Od403NDAx1DS0tzJUU8hJzU22VXHwCdN0yc4CWKymUJeaUAoUCEouL lfTtbIryS0tSFTLyi0tslVILUnIKDA0L9IoTc4tL89L1kvNzrQwNDIxMgSoTcjK2XJvOVHBa uKLjx03WBsaJAl2MHBwSAiYSRzsLuhi5OIQEdjBKnDwxkwnC+cQo8bLjEJTzjVHi1Jdmti5G TrCOaWe/QSX2MkocWLANynnCKPFh4VlGkCoWAVWJtf8egtlsAhoSt6fMZAexRYDiKxfcZQWx mQXKJX7OP8gMYgsLBEpc7/rHAmLzCuhIHFp/jB3CFpQ4OfMJWJxTQE3i9tqPjCB3iwqoSLw6 WA+yV0LgJbvEhDvHmSCuc5G4ffMJlC0s8er4FnYIW0ri87u9UB/US8y+fJIZonkC0J/n+qEa jCVmPWtnhDguQ+LV1cWMkEBSljhyiwUizCfRcfgvO0SYV6KjTQiiU1FixYmZUKvEJdoatzND 2B4S81a9hobPZmAodqxlmcAoPwvJa7OQbIOwdSQW7P7ENgtoBbOAtMTyfxwQpqbE+l36CxhZ VzGKpRYU56anFhsVGCFH9iZGcMLUctvBOOXtB71DjEwcjIcYJTiYlUR4WU/HJgjxpiRWVqUW 5ccXleakFh9iNAXG00RmKdHkfGDKziuJNzQ1MjMzsDS1MDUzslAS5y02eBAvJJCeWJKanZpa kFoE08fEwSnVwJR9/8WdlzeC+vjZi2bnsrI9E3T6YvZD4QIjC8elo9sTOe71PEv3z/x0/7XX vttiqhZ9yos/ivB0OyrbPHjMyXvMdeWO6yI+d0r12suvf/4hrn7i2dpzsrPexPbez6pgu7Nw UuOup2oySjGblszZMa8n+GEvu5npnZ/JryXO5nhoNDuUL7qardLGkrepozaZWYPz7du3S72e LL4Y1v3lyoG5XdMd1gpv8Y9fsjB0juetoykXA/LFjUMuyl5fx65tl/x9ZfXLtvodO7dxPTOe EvVwTqVWv9JJl81ZZ+JYVRiZOnzEVx5QdJZu1TvioRq2fb94+qSaGVL12u8r5oqbLA8t2KDY nTfrSnnWjH21sUosxRmJhlrMRcWJAJbq3XUhBAAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrELMWRmVeSWpSXmKPExsWy7bCSnK7U6sQEg2WN8hZz1q9hs7gy7Q+j xZRfS5ktLu+aw2Zxb81/VgdWj02rOtk8Nn2axO5xYsZvFo++LasYPT5vkgtgjeKySUnNySxL LdK3S+DKOPT/GHNBt2DF9ovyDYyveLsYOTkkBEwkpp39xtTFyMUhJLCbUeLuw4OMEAlxiadL LkDZwhL3W46wQhQ9YpT4MrcZLMEioCqx9t9DMJtNQEPi9pSZ7CC2CFB85YK7rCA2s0C5xM/5 B5lBbGGBQInrXf9YQGxeAR2JQ+uPsUMM3cwoMfPIEzaIhKDEyZlPWCCatSRu/HsJdB4HkC0t sfwfB0iYU0BN4vbaj4wgYVEBFYlXB+snMArOQtI8C0nzLITmBYzMqxglUwuKc9Nziw0LDPNS y/WKE3OLS/PS9ZLzczcxgoNdS3MH4/ZVH/QOMTJxMB5ilOBgVhLhZT0dmyDEm5JYWZValB9f VJqTWnyIUZqDRUmc90LXyXghgfTEktTs1NSC1CKYLBMHp1QD0yKf82VzXK9PUfeW1e3U6mwq vMCj/2rdv4W/1m4xEmScf6A/dUvsWTnv4rc3VRcnSpSwP9h5d/dOD1WB+b4ckZXF73mPPa+X v2XhKHBo7kGFGAd+ybsFfoFBXxrj9fvasnfGl03O/d64XUvj94VjO9bbsXas38x4l+/qlut/ HXef5vh09//dqR0bylpS91rHv22Q4DSVCwz5u0xFh72yv1L84sriVWYbBVQYG37ef7ulTtqy 5Pdte5/Fi33SjM894DF68ER6R1B6sG5Guucq06OJj+0WBF1WjxUKfpbYUWJxnn2NDcuRKTMy KyPFREsVinp0d722qgy+dtDsdb32Z+GeS0ruSnmn9ONVg9mVWIozEg21mIuKEwFnIv8r5QIA AA== X-CMS-MailID: 20210329102530epcas2p11e5de4a40264b9aeca33c89a46932b82 X-Msg-Generator: CA Content-Type: multipart/mixed; boundary="----gJqi5NNVyYI6Zwqm0SG9s49ZPiKtTbI8X5q.UcWq9Dw77Yu7=_23ab1_" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20210329054156epcas2p31650fa755e6cbcc55c4f33a79878256f References: <1616995751-83180-1-git-send-email-h10.kim@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ------gJqi5NNVyYI6Zwqm0SG9s49ZPiKtTbI8X5q.UcWq9Dw77Yu7=_23ab1_ Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline On Mon, Mar 29, 2021 at 09:34:31AM +0300, Leon Romanovsky wrote: > On Mon, Mar 29, 2021 at 02:29:10PM +0900, Hyunsoon Kim wrote: > > This patch allows programmer to avoid zero initialization on page > > allocation even when the kernel config "CONFIG_INIT_ON_ALLOC_DEFAULT" > > is enabled. The configuration is made to prevent uninitialized > > heap memory flaws, and Android has applied this for security and > > deterministic execution times. Please refer to below. > > > > https://android-review.googlesource.com/c/kernel/common/+/1235132 > > > > However, there is a case that the zeroing page memory is unnecessary > > when the page is used on specific purpose and will be zeroed > > automatically by hardware that accesses the memory through DMA. > > For instance, page allocation used for IP packet reception from Exynos > > modem is solely used for packet reception. Although the page will be > > freed eventually and reused for some other purpose, initialization at > > that moment of reuse will be sufficient to avoid uninitialized heap > > memory flaws. To support this kind of control, this patch creates new > > gfp type called ___GFP_NOINIT, that allows no zeroing at the moment > > of page allocation, called by many related APIs such as page_frag_alloc, > > alloc_pages, etc. > > > > Signed-off-by: Hyunsoon Kim > > --- > > include/linux/gfp.h | 2 ++ > > include/linux/mm.h | 4 +++- > > 2 files changed, 5 insertions(+), 1 deletion(-) > > Let's assume that we will use this new flag, and users are smart enough > to figure when it needs to be used, what will be the performance gain? > > Thanks For instance, there are four memory access (either read or write) done by the system; memory write due to page allocation for reserving memory for modem hardware, memory write on the page by modem hardware, read and write incurred by copy_to_user operation by iperf reading the incoming network data. Theoretically, we can expect 1/4 of power saving on DRAM bandwidth. By performing simple iperf test with download UDP 800Mbps, we saw 5-6mA power gain by disabling CONFIG_INIT_ON_ALLOC_DEFAULT. Thanks ------gJqi5NNVyYI6Zwqm0SG9s49ZPiKtTbI8X5q.UcWq9Dw77Yu7=_23ab1_ Content-Type: text/plain; charset="utf-8" ------gJqi5NNVyYI6Zwqm0SG9s49ZPiKtTbI8X5q.UcWq9Dw77Yu7=_23ab1_--