From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FBD0C636D4 for ; Fri, 10 Feb 2023 23:03:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 090DA280033; Fri, 10 Feb 2023 18:03:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0415928002F; Fri, 10 Feb 2023 18:03:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E72D9280033; Fri, 10 Feb 2023 18:03:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id DA64B28002F for ; Fri, 10 Feb 2023 18:03:14 -0500 (EST) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 99A2D40746 for ; Fri, 10 Feb 2023 23:03:14 +0000 (UTC) X-FDA: 80452909908.11.35359B2 Received: from mail-yb1-f181.google.com (mail-yb1-f181.google.com [209.85.219.181]) by imf24.hostedemail.com (Postfix) with ESMTP id DD085180002 for ; Fri, 10 Feb 2023 23:03:12 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="Y/D45cI+"; spf=pass (imf24.hostedemail.com: domain of surenb@google.com designates 209.85.219.181 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676070192; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qZekMNkTFFpTMCpqgivsUFbIubuqug2kR1ofGLk4G1g=; b=e4N5K/nuwXFtn/Zg212DPtw7ZTkRw748DIx496sa6yeT2NKSW8Uh5cclCXZiveGcAmTUrI Ek/+tzA0Pe7TGa1cPLYhF8EKDCsdWcMhe/w6ymsQtoA3AThg1h/CpAP/QfvHopWGuKdFb5 oS2rjT47lzaX6cJ0tfEHm2r61caQAXY= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="Y/D45cI+"; spf=pass (imf24.hostedemail.com: domain of surenb@google.com designates 209.85.219.181 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676070192; a=rsa-sha256; cv=none; b=7bxXlDyRUxS4oLbrx7FJpacQv9yiCPhhYOk87vXYYzuVDP3uH4sOWEHjWIaz8N8XphCbA2 wA27bu/i5lGosVJxVFlyaTS2pdA7t0zcjD+W3TpQ44ZxyJerw9VmcLr4Y9C0b3sCwnmeMe FF4c6PjO8r6IeMhfvLj51dT9imOUcW8= Received: by mail-yb1-f181.google.com with SMTP id x71so7240549ybg.6 for ; Fri, 10 Feb 2023 15:03:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=qZekMNkTFFpTMCpqgivsUFbIubuqug2kR1ofGLk4G1g=; b=Y/D45cI+CurTJE1dfs9zdSP830MfQ+qW4OXDd9NqQLSSL8NcXbp1WdDqTvWJikXwWR ZMlluzDaaZCkub0UGsu7DwM5wEYf9bL2dkG10Taqdlq+U8ss5oBzUUHKcCvJKNJAIQE5 9L8+3E27tpuZCgw0vIYJGUyTqb+WOpeMRJcEgRWlsb/40N333Qe5a/c5U04hS7NdpIkY wJc4BJsoOKJQnl4FCzGg8KaV7yWI123uvBWbAsIzs699tW3j8kHnaz1Z+jBXV+kXZGbY vjN3LPEa1tdlO+qTIt/GmLapuQgloNDjHc3942zHGs5h6vjbmg+kJIl1xeL94YAdElDM eZkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=qZekMNkTFFpTMCpqgivsUFbIubuqug2kR1ofGLk4G1g=; b=Zu8hAFZl57wYHZdDk2C7rpksX7f63lxHWwNRwP+xoHkv8DMAHV0P6Dbl2iHbwEuJY5 vIMI4IfdWk0KoODhzgnuIvKAJGXu2dTbfLi6Wk/N002V5dlW6smMWz3Zr9oFy33QZzH0 GGYqWq0gSuL2tRvcYSTw9LcfDZbcFifG1JpZ9HFYICuJNvC3GAbue/haM0i8fn8VBgAR EDKC32BoiK90v1o/udyMvTRLDCV5eWocQaKFU7oepIR3bvwfwzPhl6Q1BYI0luZuI40t 5wwSA5XndIb4FFhVTfPhDcBajjk6UGZHGFhC7Zz3Ii4U2D8Q6uppJ+IErqn5bUa10VaP /mJA== X-Gm-Message-State: AO0yUKUMBLSziD5D1Ws/Hi0bVLk0nJs8YYmriLSeZs48pENIhEFzR1pr rVVbCaDPtw/T+cj+h0+oB1S3ZKourwWE+AlFyQq6FA== X-Google-Smtp-Source: AK7set9IQUHzQV9y9dl6uH80Cy02KpZyGSHXJ/bJtXVB1EL2imKDfAEyqBuFVJnQHIKXhllunXtD9NrVxql2iIP1PQw= X-Received: by 2002:a5b:707:0:b0:8bc:56a2:49d8 with SMTP id g7-20020a5b0707000000b008bc56a249d8mr1070849ybq.428.1676070191832; Fri, 10 Feb 2023 15:03:11 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Suren Baghdasaryan Date: Fri, 10 Feb 2023 15:03:00 -0800 Message-ID: Subject: Re: [PATCH] psi: reduce min window size to 50ms To: Sudarshan Rajagopalan Cc: David Hildenbrand , Johannes Weiner , Mike Rapoport , Oscar Salvador , Anshuman Khandual , mark.rutland@arm.com, will@kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Trilok Soni , Sukadev Bhattiprolu , Srivatsa Vaddagiri , Patrick Daly Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: DD085180002 X-Stat-Signature: hyedtdpkgwc6uoiqpimku8czx5xx9c4w X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676070192-755476 X-HE-Meta: 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 hXdTMiYO xcHLY2dLagbzjeMM/S74IvmtUY319TG6Lhl/DELHGo5dvuBC5TsQVz3Xsuk8mthF4FTYdnvz0Ee55jjK6WXoZCO51dvAo+lOY5wxcT/pCX6M9bmbqkTulyD6ExJnaTHbsEqTEt+AY+EDQlv0PRblElLtRbOi3CmhvotzjaZVvYZLFusNYilsBRPK6vMrv0q+7txucJ1Jp1zyX85betFpMVgrtkJZhiKv4p5IDzqY8RbLssgVolOk7uUgzTOh/uIjeY/wPQJnynuIV3/rnVfErgyR7q/V4V1f9Fr/bX5vZGj+sL+czHWtFr7Brng== X-Bogosity: Ham, tests=bogofilter, spamicity=0.027362, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Feb 10, 2023 at 2:31 PM Sudarshan Rajagopalan wrote: > > The PSI mechanism is useful tool to monitor pressure stall > information in the system. Currently, the minimum window size > is set to 500ms. May we know what is the rationale for this? The limit was set to avoid regressions in performance and power consumption if the window is set too small and the system ends up polling too frequently. That said, the limit was chosen based on results of specific experiments which might not represent all usecases. If you want to change this limit, you would need to describe why the new limit is inherently better than the current one (why not higher, why not lower). Thanks, Suren. > > For lightweight systems such as Linux Embedded Systems, PSI > can be used to monitor and track memory pressure building up > in the system and respond quickly to such memory demands. > Example, the Linux Embedded Systems could be a secondary VM > system which requests for memory from Primary host. With 500ms > window size, the sampling period is 50ms (one-tenth of windwo > size). So the minimum amount of time the process needs to stall, > so that a PSI event can be generated and actions can be done > is 50ms. This reaction time can be much reduced by reducing the > sampling time (by reducing window size), so that responses to > such memory pressures in system can be serviced much quicker. > > Please let us know your thoughts on reducing window size to 50ms. > > Sudarshan Rajagopalan (1): > psi: reduce min window size to 50ms > > kernel/sched/psi.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > -- > 2.7.4 >