From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mslow3.mail.gandi.net (mslow3.mail.gandi.net [217.70.178.249]) (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 5A2FE145355 for ; Mon, 13 Apr 2026 18:31:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.178.249 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776105104; cv=none; b=BL+aBmn4ZksC3zzsmmfQC8P8wbfxrDmazSXx4yNdUK6bNMosCmKFl50l+fIIo+VCimTOqybL7N1xrT4gCDFur0xbQKj0rufH1VMoi3D1BXN9H6t8cncijsRakAhthamYnXE1USH8KBpJC9SKF9hRz2/rRGd1FCZ/5lDfT9k3x8E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776105104; c=relaxed/simple; bh=vzNp3QFD5c5MNSaOz/rHRdWr/iIKfoYJmtbtHk760PI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=hUC3wdbvAY44NEL/TpsZQ/UlOmm2CY0KNWbVK+xj485/yb6y8ISKa6zNlynUsqYrIdRcBG90MkEhAv2H8ZsvDvJoAKoF6pzpPuIm7VQtKQVt80dR65g6l7ibCxgICvfCTU76GoOsWEx+Xcmz3ANOA5ubzTwQX9Oo5prhHs2yxwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org; spf=pass smtp.mailfrom=xenomai.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b=g8rYXG/i; arc=none smtp.client-ip=217.70.178.249 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xenomai.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b="g8rYXG/i" Received: from relay8-d.mail.gandi.net (relay8-d.mail.gandi.net [217.70.183.201]) by mslow3.mail.gandi.net (Postfix) with ESMTP id 54935580351 for ; Mon, 13 Apr 2026 18:31:40 +0000 (UTC) Received: by mail.gandi.net (Postfix) with ESMTPSA id 36A163EC8F; Mon, 13 Apr 2026 18:31:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xenomai.org; s=gm1; t=1776105092; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QzOn7socQyGoLfkBxZ/GeUKj0KBCAaXw0SYDfrIXpIQ=; b=g8rYXG/iMlO2N9zG8oahbjnhMl6D4sM0I/s5FG+hhHPvfqNVBUrlR/QzwXJ1IgoblFoYA5 iU8IwpKOcrrJBXEHQKErpzlbO79h3AF80qz5lZ92XffCLgeuBmFQtzGAvwG/W8HRLYXcPK FSi5KjMjchxHCmDj+ySHUc4G3szuL9d3C+6kSTy3wtaaFCT3PecqGQHzJI+r0QXR+13GIj rXhvF7iISzV0JytxOR43xMTLTBEDmu0qekJiReFG6k4TCJWzAbxM+9Hw2E7PmrGgg3O5ny y3ryqEuVScCcYdH1PqvZWYOCeVHN5qVBKr74iCwx2e5vWR71WgYri2K1Ti7EsA== From: Philippe Gerum To: Brandon Ho Cc: brho@relativityspace.com, jsridharan@relativityspace.com, xenomai@lists.linux.dev Subject: Re: Minor page faults from memory compaction causing in-band transitions In-Reply-To: <20260413181929.1801013-1-brho@relativityspace.com> (Brandon Ho's message of "Mon, 13 Apr 2026 11:19:29 -0700") References: <87v7e8yzhj.fsf@xenomai.org> <20260413181929.1801013-1-brho@relativityspace.com> User-Agent: mu4e 1.12.12; emacs 30.2 Date: Mon, 13 Apr 2026 20:31:31 +0200 Message-ID: <87h5pe7lvg.fsf@xenomai.org> Precedence: bulk X-Mailing-List: xenomai@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-GND-Sasl: rpm@xenomai.org X-GND-Cause: 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 X-GND-State: clean X-GND-Score: -100 Brandon Ho writes: > Thank you for the responses! I recently came across the > `compact_unevictable_allowed` sysctl option and it seems like it could be a > good fit for our use case. Setting it to 0 would prevent the kernel from > compacting/migrating locked pages, which should eliminate the minor faults > we're seeing during compaction. > > Could we possibly set `compact_unevictable_allowed=0` by default when > CONFIG_EVL is enabled? Definitely, yes. Thanks for chasing this issue down. This patch is going to be merged upstream asap, you may want to apply it for a preview. diff --git a/mm/Kconfig b/mm/Kconfig index 7bf469354faf3..759af896a5c7b 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -648,7 +648,7 @@ config COMPACTION config COMPACT_UNEVICTABLE_DEFAULT int depends on COMPACTION - default 0 if PREEMPT_RT + default 0 if PREEMPT_RT || DOVETAIL default 1 # > > https://www.infradead.org/~mchehab/kernel_docs/admin-guide/sysctl/vm.html#compact-unevictable-allowed -- Philippe.