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 <h10.kim@xxxxxxxxxxx> > --- > 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
