From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx124.postini.com [74.125.245.124]) by kanga.kvack.org (Postfix) with SMTP id 4107E6B0037 for ; Tue, 27 Aug 2013 18:24:24 -0400 (EDT) Date: Tue, 27 Aug 2013 15:24:21 -0700 From: Andrew Morton Subject: Re: [PATCH v2 7/7] mm: munlock: manual pte walk in fast path instead of follow_page_mask() Message-Id: <20130827152421.4f546507364eb9da7fd5add0@linux-foundation.org> In-Reply-To: <1376915022-12741-8-git-send-email-vbabka@suse.cz> References: <1376915022-12741-1-git-send-email-vbabka@suse.cz> <1376915022-12741-8-git-send-email-vbabka@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: =?ISO-8859-1?Q?J=F6rn?= Engel , Michel Lespinasse , Hugh Dickins , Rik van Riel , Johannes Weiner , Mel Gorman , Michal Hocko , linux-mm@kvack.org On Mon, 19 Aug 2013 14:23:42 +0200 Vlastimil Babka wrote: > Currently munlock_vma_pages_range() calls follow_page_mask() to obtain each > struct page. This entails repeated full page table translations and page table > lock taken for each page separately. > > This patch attempts to avoid the costly follow_page_mask() where possible, by > iterating over ptes within single pmd under single page table lock. The first > pte is obtained by get_locked_pte() for non-THP page acquired by the initial > follow_page_mask(). The latter function is also used as a fallback in case > simple pte_present() and vm_normal_page() are not sufficient to obtain the > struct page. mm/mlock.c: In function 'munlock_vma_pages_range': mm/mlock.c:388: warning: 'pmd_end' may be used uninitialized in this function As far as I can tell, this is notabug, but I'm not at all confident in that - the protocol for locals `pte' and `pmd_end' is bizarre. The function is fantastically hard to follow and deserves to be dragged outside, shot repeatedly then burned. Could you please, as a matter of some urgency, take a look at rewriting the entire thing so that it is less than completely insane? -- 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