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Sat, 18 May 2024 17:47:19 -0700 (PDT) Received: from [2620:0:1008:15:15d8:f72b:f347:b61c] ([2620:0:1008:15:15d8:f72b:f347:b61c]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-6340ca9019esm15042359a12.50.2024.05.18.17.47.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 May 2024 17:47:18 -0700 (PDT) Date: Sat, 18 May 2024 17:47:16 -0700 (PDT) From: David Rientjes To: Sourav Panda cc: corbet@lwn.net, gregkh@linuxfoundation.org, rafael@kernel.org, akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, rppt@kernel.org, david@redhat.com, rdunlap@infradead.org, chenlinxuan@uniontech.com, yang.yang29@zte.com.cn, tomas.mudrunka@gmail.com, bhelgaas@google.com, ivan@cloudflare.com, pasha.tatashin@soleen.com, yosryahmed@google.com, hannes@cmpxchg.org, shakeelb@google.com, kirill.shutemov@linux.intel.com, wangkefeng.wang@huawei.com, adobriyan@gmail.com, vbabka@suse.cz, Liam.Howlett@oracle.com, surenb@google.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, weixugc@google.com Subject: Re: [PATCH v12] mm: report per-page metadata information In-Reply-To: <20240512010611.290464-1-souravpanda@google.com> Message-ID: <45fb4c94-dd77-94c3-f08f-81bf31e6d6d2@google.com> References: <20240512010611.290464-1-souravpanda@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0B16940006 X-Stat-Signature: ep7s8u5ys4opndrado1937x5thzxdxau X-HE-Tag: 1716079640-61355 X-HE-Meta: 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 7qRuFnJW 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.186266, 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 Sun, 12 May 2024, Sourav Panda wrote: > Today, we do not have any observability of per-page metadata > and how much it takes away from the machine capacity. Thus, > we want to describe the amount of memory that is going towards > per-page metadata, which can vary depending on build > configuration, machine architecture, and system use. > > This patch adds 2 fields to /proc/vmstat that can used as shown > below: > > Accounting per-page metadata allocated by boot-allocator: > /proc/vmstat:nr_memmap_boot * PAGE_SIZE > > Accounting per-page metadata allocated by buddy-allocator: > /proc/vmstat:nr_memmap * PAGE_SIZE > > Accounting total Perpage metadata allocated on the machine: > (/proc/vmstat:nr_memmap_boot + > /proc/vmstat:nr_memmap) * PAGE_SIZE > > Utility for userspace: > > Observability: Describe the amount of memory overhead that is > going to per-page metadata on the system at any given time since > this overhead is not currently observable. > > Debugging: Tracking the changes or absolute value in struct pages > can help detect anomalies as they can be correlated with other > metrics in the machine (e.g., memtotal, number of huge pages, > etc). > > page_ext overheads: Some kernel features such as page_owner > page_table_check that use page_ext can be optionally enabled via > kernel parameters. Having the total per-page metadata information > helps users precisely measure impact. Furthermore, page-metadata > metrics will reflect the amount of struct pages reliquished > (or overhead reduced) when hugetlbfs pages are reserved which > will vary depending on whether hugetlb vmemmap optimization is > enabled or not. > > For background and results see: > lore.kernel.org/all/20240220214558.3377482-1-souravpanda@google.com > > Signed-off-by: Sourav Panda > Reviewed-by: Pasha Tatashin Acked-by: David Rientjes