From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id 68F546B007E for ; Tue, 19 Apr 2016 12:07:22 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id p188so23984493oih.2 for ; Tue, 19 Apr 2016 09:07:22 -0700 (PDT) Received: from mail-io0-x242.google.com (mail-io0-x242.google.com. [2607:f8b0:4001:c06::242]) by mx.google.com with ESMTPS id 6si1114790otv.3.2016.04.19.09.07.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Apr 2016 09:07:21 -0700 (PDT) Received: by mail-io0-x242.google.com with SMTP id s2so3248594iod.3 for ; Tue, 19 Apr 2016 09:07:21 -0700 (PDT) MIME-Version: 1.0 Date: Wed, 20 Apr 2016 00:07:21 +0800 Message-ID: Subject: mm: Page allocation from buddy system might delay the tasks on different SMP cores From: GeHao Kang Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: mel@csn.ul.ie Cc: linux-mm@kvack.org Hi Mel, Through my experiment in SMP system, I find the mm_page_alloc_zone_locked event produced by the fork system call on one CPU might delay the task on another CPU. According to the events-keme.txt in kernel documents, the interrupts are disabled and cache lines between CPUs are dirtied when this event happens. Therefore, I am afraid that a task might be interfered by the tasks on different CPUs which at the same time request memory from the buddy allocator. My questions are as follows: * Is it necessary to disable interrupts when allocating/freeing memory from buddy system? * Why the cache lines between CPUs are dirtied by the allocation in buddy system? Thanks, - Kang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org