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X-IronPort-AV: E=McAfee;i="6600,9927,10960"; a="61404" X-IronPort-AV: E=Sophos;i="6.05,211,1701158400"; d="scan'208";a="61404" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jan 2024 02:13:23 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,211,1701158400"; d="scan'208";a="1164931" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.54.38.190]) by orviesa005.jf.intel.com with ESMTP; 22 Jan 2024 02:13:24 -0800 Received: by tassilo.localdomain (Postfix, from userid 1000) id 9563F301BE1; Mon, 22 Jan 2024 02:13:23 -0800 (PST) From: Andi Kleen To: linux-xfs@vger.kernel.org, david@fromorbit.com, linux-mm@kvack.org References: <20240118222216.4131379-1-david@fromorbit.com> Date: Mon, 22 Jan 2024 02:13:23 -0800 In-Reply-To: <20240118222216.4131379-1-david@fromorbit.com> (Dave Chinner's message of "Fri, 19 Jan 2024 09:19:38 +1100") Message-ID: <87zfwxk75o.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B48321A0004 X-Stat-Signature: xqno7gbjfsbxwi44gxxda9n5u19etpfn X-Rspam-User: X-HE-Tag: 1705918405-956267 X-HE-Meta: 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 5pIKp9gq GQhdlKWRU8MZYhqLE0/rJyfnezrsoCR5hu32tj3xxGd4YaxkkZFbIjm1d2OqMMzTYph8MwldZfowJCKG5+G+iuvinJ2DKZuSLA8lMR9rWIXUVp4/eLFwiuRd8lQIroh97BWGWQ/JXiVDvTqngimLbkZXew9SaZUMVJbFiV/jDJL75iYaS6q1xTzWbeTa+VvimY53M X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Dave Chinner writes: > Thoughts, comments, etc? The interesting part is if it will cause additional tail latencies allocating under fragmentation with direct reclaim, compaction etc. being triggered before it falls back to the base page path. In fact it is highly likely it will, the question is just how bad it is. Unfortunately benchmarking for that isn't that easy, it needs artificial memory fragmentation and then some high stress workload, and then instrumenting the transactions for individual latencies. I would in any case add a tunable for it in case people run into this. Tail latencies are a common concern on many IO workloads. -Andi