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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251216153604.0c00504223d3fad070f2e803@linux-foundation.org> X-Stat-Signature: s49s8ryywon44j1t1tu74iwwbros7xsy X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 1D25F4000D X-Rspam-User: X-HE-Tag: 1765971454-26645 X-HE-Meta: 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 WgwnX34b 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 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: List-Subscribe: List-Unsubscribe: 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