From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f169.google.com (mail-pd0-f169.google.com [209.85.192.169]) by kanga.kvack.org (Postfix) with ESMTP id BB1769003C8 for ; Wed, 22 Jul 2015 19:05:22 -0400 (EDT) Received: by pdrg1 with SMTP id g1so145783826pdr.2 for ; Wed, 22 Jul 2015 16:05:22 -0700 (PDT) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTP id pj10si6948430pac.162.2015.07.22.16.05.21 for ; Wed, 22 Jul 2015 16:05:21 -0700 (PDT) Message-ID: <55B021B1.5020409@intel.com> Date: Wed, 22 Jul 2015 16:05:21 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH] mm: Flush the TLB for a single address in a huge page References: <1437585214-22481-1-git-send-email-catalin.marinas@arm.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas , David Rientjes Cc: linux-mm , Linux Kernel Mailing List , Andrew Morton , Andrea Arcangeli On 07/22/2015 03:48 PM, Catalin Marinas wrote: > You are right, on x86 the tlb_single_page_flush_ceiling seems to be > 33, so for an HPAGE_SIZE range the code does a local_flush_tlb() > always. I would say a single page TLB flush is more efficient than a > whole TLB flush but I'm not familiar enough with x86. The last time I looked, the instruction to invalidate a single page is more expensive than the instruction to flush the entire TLB. We also don't bother doing ranged flushes _ever_ for hugetlbfs TLB invalidations, but that was just because the work done around commit e7b52ffd4 didn't see any benefit. That said, I can't imagine this will hurt anything. We also have TLBs that can mix 2M and 4k pages and I don't think we did back when we put that code in originally. -- 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