Date: Sun, 11 Feb 2018 13:16:46 -0800 From: Matthew Wilcox <willy@...radead.org> To: Igor Stoppa <igor.stoppa@...wei.com> Cc: rdunlap@...radead.org, corbet@....net, keescook@...omium.org, mhocko@...nel.org, labbott@...hat.com, jglisse@...hat.com, hch@...radead.org, cl@...ux.com, linux-security-module@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH 3/6] struct page: add field for vm_struct On Sun, Feb 11, 2018 at 05:19:17AM +0200, Igor Stoppa wrote: > The struct page has a "mapping" field, which can be re-used, to store a > pointer to the parent area. This will avoid more expensive searches. > > As example, the function find_vm_area is reimplemented, to take advantage > of the newly introduced field. Umm. Is it more efficient? You're replacing an rb-tree search with a page-table walk. You eliminate a spinlock, which is great, but is the page-table walk more efficient? I suppose it'll depend on the depth of the rb-tree, and (at least on x86), the page tables should already be in cache. Unrelated to this patch, I'm working on a patch to give us page_type, and I think I'll allocate a bit to mark pages which are vmalloced.
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