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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d8eeb132e1sm49707756d6.35.2024.12.10.14.05.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Dec 2024 14:05:47 -0800 (PST) From: Gregory Price To: x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org Cc: linux-cxl@vger.kernel.org, kernel-team@meta.com, dan.j.williams@intel.com, ira.weiny@intel.com, gourry@gourry.net, dave.hansen@linux.intel.com, david@redhat.com, rppt@kernel.org, akpm@linux-foundation.org, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, osalvador@suse.de, Fan Ni Subject: [PATCH v7 2/3] x86: probe memory block size advisement value during mm init Date: Tue, 10 Dec 2024 17:05:16 -0500 Message-ID: <20241210220517.3744-3-gourry@gourry.net> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241210220517.3744-1-gourry@gourry.net> References: <20241210220517.3744-1-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Systems with hotplug may provide an advisement value on what the memblock size should be. Probe this value when the rest of the configuration values are considered. The new heuristic is as follows 1) set_memory_block_size_order value if already set (cmdline param) 2) minimum block size if memory is less than large block limit 3) if no hotplug advice: Max block size if system is bare-metal, otherwise use end of memory alignment. 4) if hotplug advice: lesser of advice and end of memory alignment. Convert to cpu_feature_enabled() while at it.[1] [1] https://lore.kernel.org/all/20241031103401.GBZyNdGQ-ZyXKyzC_z@fat_crate.local/ Suggested-by: Borislav Petkov Suggested-by: David Hildenbrand Signed-off-by: Gregory Price Acked-by: David Hildenbrand Acked-by: Dave Hansen Acked-by: Mike Rapoport (Microsoft) Acked-by: Dan Williams Tested-by: Fan Ni --- arch/x86/mm/init_64.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 01ea7c6df303..58ace82874eb 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1462,16 +1462,21 @@ static unsigned long probe_memory_block_size(void) } /* - * Use max block size to minimize overhead on bare metal, where - * alignment for memory hotplug isn't a concern. + * When hotplug alignment is not a concern, maximize blocksize + * to minimize overhead. Otherwise, align to the lesser of advice + * alignment and end of memory alignment. */ - if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) { + bz = memory_block_advised_max_size(); + if (!bz) { bz = MAX_BLOCK_SIZE; - goto done; + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + goto done; + } else { + bz = max(min(bz, MAX_BLOCK_SIZE), MIN_MEMORY_BLOCK_SIZE); } /* Find the largest allowed block size that aligns to memory end */ - for (bz = MAX_BLOCK_SIZE; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { + for (; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { if (IS_ALIGNED(boot_mem_end, bz)) break; }