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Shutemov" Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Tetsuo Handa , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] mm: avoid slub allocation while holding list_lock Message-ID: <20190912013100.GA114178@google.com> References: <20190911071331.770ecddff6a085330bf2b5f2@linux-foundation.org> <20190912002929.78873-1-yuzhao@google.com> <20190912002929.78873-2-yuzhao@google.com> <20190912004401.jdemtajrspetk3fh@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190912004401.jdemtajrspetk3fh@box> User-Agent: Mutt/1.10.1 (2018-07-13) 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: On Thu, Sep 12, 2019 at 03:44:01AM +0300, Kirill A. Shutemov wrote: > On Wed, Sep 11, 2019 at 06:29:28PM -0600, Yu Zhao wrote: > > If we are already under list_lock, don't call kmalloc(). Otherwise we > > will run into deadlock because kmalloc() also tries to grab the same > > lock. > > > > Instead, statically allocate bitmap in struct kmem_cache_node. Given > > currently page->objects has 15 bits, we bloat the per-node struct by > > 4K. So we waste some memory but only do so when slub debug is on. > > Why not have single page total protected by a lock? > > Listing object from two pages at the same time doesn't make sense anyway. > Cuncurent validating is not something sane to do. Okay, cutting down to static global bitmap.