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Wed, 17 Dec 2025 03:37:31 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 17 Dec 2025 12:37:29 +0100 To: Andrew Morton Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Vishal Moola , Ryan Roberts , Dev Jain , Baoquan He , LKML Subject: Re: [PATCH 2/2] mm/vmalloc: Add attempt_larger_order_alloc parameter Message-ID: References: <20251216211921.1401147-1-urezki@gmail.com> <20251216211921.1401147-2-urezki@gmail.com> <20251216153604.0c00504223d3fad070f2e803@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251216153604.0c00504223d3fad070f2e803@linux-foundation.org> On Tue, Dec 16, 2025 at 03:36:04PM -0800, Andrew Morton wrote: > On Tue, 16 Dec 2025 22:19:21 +0100 "Uladzislau Rezki (Sony)" wrote: > > > Introduce a module parameter to enable or disable the large-order > > allocation path in vmalloc. High-order allocations are disabled by > > default so far, but users may explicitly enable them at runtime if > > desired. > > > > High-order pages allocated for vmalloc are immediately split into > > order-0 pages and later freed as order-0, which means they do not > > feed the per-CPU page caches. As a result, high-order attempts tend > > to bypass the PCP fastpath and fall back to the buddy allocator that > > can affect performance. > > > > However, when the PCP caches are empty, high-order allocations may > > show better performance characteristics especially for larger > > allocation requests. > > > > Since the best strategy is workload-dependent, this patch adds a > > parameter letting users to choose whether vmalloc should try > > high-order allocations or stay strictly on the order-0 fastpath. > > > > ... > > > > +module_param(attempt_larger_order_alloc, int, 0644); > > We should have user docs, please. Probably in kernel-parameters.txt. > Thanks. I will add it. -- Uladzislau Rezki