From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f182.google.com (mail-pd0-f182.google.com [209.85.192.182]) by kanga.kvack.org (Postfix) with ESMTP id 905286B0031 for ; Fri, 4 Oct 2013 14:33:23 -0400 (EDT) Received: by mail-pd0-f182.google.com with SMTP id r10so4360123pdi.41 for ; Fri, 04 Oct 2013 11:33:23 -0700 (PDT) Date: Fri, 4 Oct 2013 20:33:15 +0200 From: Jan Kara Subject: Re: [PATCH 23/26] ib: Convert qib_get_user_pages() to get_user_pages_unlocked() Message-ID: <20131004183315.GA19557@quack.suse.cz> References: <1380724087-13927-1-git-send-email-jack@suse.cz> <1380724087-13927-24-git-send-email-jack@suse.cz> <32E1700B9017364D9B60AED9960492BC211B0176@FMSMSX107.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32E1700B9017364D9B60AED9960492BC211B0176@FMSMSX107.amr.corp.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Marciniszyn, Mike" Cc: Jan Kara , LKML , "linux-mm@kvack.org" , infinipath , Roland Dreier , "linux-rdma@vger.kernel.org" On Fri 04-10-13 13:52:49, Marciniszyn, Mike wrote: > > Convert qib_get_user_pages() to use get_user_pages_unlocked(). This > > shortens the section where we hold mmap_sem for writing and also removes > > the knowledge about get_user_pages() locking from ipath driver. We also fix > > a bug in testing pinned number of pages when changing the code. > > > > This patch and the sibling ipath patch will nominally take the mmap_sem > twice where the old routine only took it once. This is a performance > issue. It will take mmap_sem only once during normal operation. Only if get_user_pages_unlocked() fail, we have to take mmap_sem again to undo the change of mm->pinned_vm. > Is the intent here to deprecate get_user_pages()? Well, as much as I'd like to, there are really places in mm code which need to call get_user_pages() while holding mmap_sem to be able to inspect corresponding vmas etc. So I want to reduce get_user_pages() use as much as possible but I'm not really hoping in completely removing it. > I agree, the old code's lock limit test is broke and needs to be fixed. > I like the elimination of the silly wrapper routine! > > Could the lock limit test be pushed into another version of the wrapper > so that there is only one set of mmap_sem transactions? I'm sorry, I don't understand what you mean here... Honza -- Jan Kara SUSE Labs, CR -- 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