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bh=8+80y47QSWOvbKO/38h2ooL7X2lhtxzCV052gx173Cs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s9f+e7XR94xtnbODov82DRWMQQaabqcIaW+nbvJthodigBYPKD5BSr1SLDRkJtKN4 NdbAbDH3YhM30vh+sWk+EgRlEpTqcrzdkdx8CJ6hoP/3JBguYbpfbYq61zA6TCZaST WLqSYTtfPrKcU9epkKPLt4M5AWJO36cufP5G5IuNnhYi1gw4u4XbXlpEa2P8z0wsER J0dvzF9e8UrMUcvJD9QonNIBE6HyDn6IcQQxKPLPbm+dFh231QDWi1AMccO9+p0HYS 6O6rPIoyXatSX+PU0aIDA9Dc5sM8qcfDewvKufzj3x5E0BltpU43RlZkGfW056AVxS QUjc3U5Uyt2zA== Date: Fri, 19 May 2023 11:29:45 +0300 From: Mike Rapoport To: Kent Overstreet Cc: Song Liu , linux-mm@kvack.org, Andrew Morton , Dave Hansen , Peter Zijlstra , Rick Edgecombe , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [RFC PATCH 1/5] mm: intorduce __GFP_UNMAPPED and unmapped_alloc() Message-ID: <20230519082945.GE4967@kernel.org> References: <20230308094106.227365-1-rppt@kernel.org> <20230308094106.227365-2-rppt@kernel.org> <20230518152354.GD4967@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 5575D160011 X-Rspam-User: X-Stat-Signature: 7nyck74cppf54taaihu5yy5ma8o6cadh X-Rspamd-Server: rspam01 X-HE-Tag: 1684485001-809554 X-HE-Meta: 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 Dm2ftt37 O4N0630axVmubn5zjzAYy8e7qyTRZOebDQyCNRuWj9EjgN3vum9DVOexmdoPmCLE99RwsvZe7XKm7yJ9bDgmDIGMVOOkXWFbQb8SCiDP/qXZS2F+Bi6Qz2UisXqjVhC2hgfT4vh5tU3+bD2JQ13HGQRLIwuE82O7Rrt+C9YXDX14slkV74NUt+Bow/GsTHu4txDf16NiQNtaV2y2CF9k0WTLfWRSQH5ea+Aw8d7fiK6JLTj2UTvhZlQXZXHFU99KaX+fw9n5bml9m7G0FmQm1y5c1FhHkZDaKhl2MbpZbeggAL6zGKbPlFORY5cZE/sZTeU7nymvcaRnXiVyGYIlrqsruDA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Kent, On Thu, May 18, 2023 at 01:23:56PM -0400, Kent Overstreet wrote: > On Thu, May 18, 2023 at 10:00:39AM -0700, Song Liu wrote: > > On Thu, May 18, 2023 at 9:48 AM Kent Overstreet > > wrote: > > > > > > On Thu, May 18, 2023 at 09:33:20AM -0700, Song Liu wrote: > > > > I am working on patches based on the discussion in [1]. I am planning to > > > > send v1 for review in a week or so. > > > > > > Hey Song, I was reviewing that thread too, > > > > > > Are you taking a different approach based on Thomas's feedback? I think > > > he had some fair points in that thread. > > > > Yes, the API is based on Thomas's suggestion, like 90% from the discussions. > > > > > > > > My own feeling is that the buddy allocator is our tool for allocating > > > larger variable sized physically contiguous allocations, so I'd like to > > > see something based on that - I think we could do a hybrid buddy/slab > > > allocator approach, like we have for regular memory allocations. > > > > I am planning to implement the allocator based on this (reuse > > vmap_area logic): > > Ah, you're still doing vmap_area approach. > > Mike's approach looks like it'll be _much_ lighter weight and higher > performance, to me. vmalloc is known to be slow compared to the buddy > allocator, and with Mike's approach we're only modifying mappings once > per 2 MB chunk. > > I don't see anything in your code for sub-page sized allocations too, so > perhaps I should keep going with my slab allocator. Your allocator implicitly relies on vmalloc because of module_alloc ;-) What I was thinking is that we can replace module_alloc() calls in your allocator with something based on my unmapped_alloc(). If we make the part that refills the cache also take care of creating the mapping in the module address space, that should cover everything. > Could you share your thoughts on your approach vs. Mike's? I'm newer to > this area of the code than you two so maybe there's an angle I've missed > :) > -- Sincerely yours, Mike.