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b=w1HTD9m4xQJi4FjFB+OIdrFkPGm2WlFfCHgcYBPv4hKlcT8DILY7zKXKD7HqGG7cl TiMrdS9wDqPW6m3wnxKWld3vmh4HM7BoW1J+7YDGPNYXiV/yidBEJJnMm1ra4suURX R5NPnZEUdsyFcnh/YN+5RJth09f2buKgejmhCj98= Date: Fri, 27 Feb 2026 12:28:57 -0800 From: Andrew Morton To: Benjamin Lee McQueen Cc: david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmpressure: scale window size based on machine memory and CPU count Message-Id: <20260227122857.dca67a5f281e39a3e78acc74@linux-foundation.org> In-Reply-To: <20260227163333.6394-1-mcq@disroot.org> References: <20260227163333.6394-1-mcq@disroot.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: BF5CAA0013 X-Rspamd-Server: rspam07 X-Stat-Signature: haszdw6gsc5oyt5ntthostwcyrdcecm9 X-Rspam-User: X-HE-Tag: 1772224139-996620 X-HE-Meta: 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 VcUJ68x/ sIygsQUP7dpF0GQbuYz2LD9wBtbM6M/xkPZusMONOG5Ejx3CZX72G9TprcrRpDTCT96a+C6NW7DzWsVsH1p3TSTO/DxZrxLAwgNldh2qUMm6K/By/JzlLiQI/+RjKuA1kwiqiy5jhtmC34b7aSRNYzH/91q0Cx9A2gCEiOCvoKhgrWakCPwdWK3Y2OxCYd7F0jVNa3ImQEj48iaDPXBwE+pqoA3XrNFWCXOnOPHZdDqrfyw4JPNvXHJ/XDk9j6LnNz6P7ON9GIHlHwIruX94ZgMCWTZHUfpRZDvtKJ3ezxTWeQMksJXTw6Y2HDA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 27 Feb 2026 10:33:33 -0600 Benjamin Lee McQueen wrote: > the vmpressure window size was recently fixed at 512 pages regardless > of machine size, this patch makes it scale based on the machine memory > and CPU count. Why? Presumably the current code is causing some problem - please fully describe that. > --- a/mm/vmpressure.c > +++ b/mm/vmpressure.c > @@ -32,10 +32,20 @@ > * As the vmscan reclaimer logic works with chunks which are multiple of > * SWAP_CLUSTER_MAX, it makes sense to use it for the window size as well. > * > - * TODO: Make the window size depend on machine size, as we do for vmstat > - * thresholds. Currently we set it to 512 pages (2MB for 4KB pages). > + * Window size is now scaled based on RAM and CPU size, similarly to how > + * vmstat checks them. > */ > -static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16; > +static unsigned long vmpressure_win; > + > +static int __init vmpressure_win_init(void) > +{ > + unsigned long mem = totalram_pages() >> (27 - PAGE_SHIFT); > + > + vmpressure_win = SWAP_CLUSTER_MAX * max(16UL, > + 2UL * fls(num_online_cpus()) * (1 + fls(mem))); > + return 0; > +} > +core_initcall(vmpressure_win_init); Whitespace is odd.