From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5D7828488F for ; Thu, 23 Jul 2026 12:51:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784811073; cv=none; b=UT56kVv1s0DofY78NAKjiGGam26vCVHtADrwhF8sbMmGdpGZPpPL1R3GjHmUTLZtd2u1F1onJyEZaaGXeHHbe4x2d8IA2ukllrlUCQyzKT8caAIrLjycb8vV6TV9YjFw1iynZerfR7dXzIrmmO5O5PvFB1pTQrswOWa9QnxBELg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784811073; c=relaxed/simple; bh=ZHzJt5yr9XR8XKjlfvXHxCg47wu84r6JkT9Tuv6M8LA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=fYm6z43PPeZ4lis+OTWxr8e1xVqsf41HiSwHn1ixuHOjuCyGDiURVAZFrNifOxZS2zCWCH5D5exi9BiN2kqlVu5VbeelDUuBh3YYoFbTZc2gVX0vDMx73foICW74YTlgCXtFBpVl5mXANwpNeOKYgAmjJCePIWXZbZn1pUcb9Dc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=wgGA8atQ; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="wgGA8atQ" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784811059; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=syMYcAbG7GBcE53aHGp1ZkfMuwv7fI9MyytwGfh2LRY=; b=wgGA8atQDNgk3Szc93kYjV8lppZoZ6QAb/81VdcLZyhjV+K7VaSemsCbjzL3sdv8Xj+CVW rE5HHu55gwzbpukvSB1iJ3VWrNAO+8H5mPjTNgqsSvS2h7i7vpfp1O1YCTGaXAPoS957VY 9/Fgva3xoy+/NkmAhZS1n9k00SupffA= From: Tao Cui To: Johannes Weiner , Suren Baghdasaryan Cc: linux-doc@vger.kernel.org, Peter Zijlstra , Jonathan Corbet , Tao Cui , linux-kernel@vger.kernel.org, cui.tao@linux.dev Subject: [PATCH] docs: accounting/psi: drop stale 500ms window minimum from trigger docs Date: Thu, 23 Jul 2026 20:50:25 +0800 Message-ID: <20260723125025.457841-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tao Cui psi.rst says trigger windows range "from 500ms to 10s" with a 50ms min polling interval. That minimum was removed in commit 519fabc7aaba ("psi: remove 500ms min window size limitation for triggers"): the polling-rate protection moved to gating trigger creation behind CAP_SYS_RESOURCE, which also stopped capping psi event latency. Update the wording accordingly: windows up to 10s with no enforced minimum; trigger creation requires CAP_SYS_RESOURCE on cgroup pressure files, while unprivileged users on /proc/pressure/ are limited to 2s multiples. Signed-off-by: Tao Cui --- Documentation/accounting/psi.rst | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/Documentation/accounting/psi.rst b/Documentation/accounting/psi.rst index d455db3e5808..aae57fb5f15c 100644 --- a/Documentation/accounting/psi.rst +++ b/Documentation/accounting/psi.rst @@ -99,15 +99,14 @@ psi metric and deactivates upon exit from the stall state. While system is in the stall state psi signal growth is monitored at a rate of 10 times per tracking window. -The kernel accepts window sizes ranging from 500ms to 10s, therefore min -monitoring update interval is 50ms and max is 1s. Min limit is set to -prevent overly frequent polling. Max limit is chosen as a high enough number -after which monitors are most likely not needed and psi averages can be used -instead. - -Unprivileged users can also create monitors, with the only limitation that the -window size must be a multiple of 2s, in order to prevent excessive resource -usage. +The kernel accepts window sizes up to 10s. The 10s maximum is chosen as a +high enough number after which monitors are most likely not needed and psi +averages can be used instead. + +To prevent excessive resource usage, trigger creation is restricted to +privileged users (CAP_SYS_RESOURCE) on cgroup pressure files; on the +system-wide /proc/pressure/ files unprivileged users can create monitors +as well, limited to window sizes that are a multiple of 2s. When activated, psi monitor stays active for at least the duration of one tracking window to avoid repeated activations/deactivations when system is -- 2.43.0