From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 3B7BC6B006A for ; Fri, 8 Oct 2010 00:40:11 -0400 (EDT) Received: from wpaz13.hot.corp.google.com (wpaz13.hot.corp.google.com [172.24.198.77]) by smtp-out.google.com with ESMTP id o984e8wE023819 for ; Thu, 7 Oct 2010 21:40:09 -0700 Received: from pxi5 (pxi5.prod.google.com [10.243.27.5]) by wpaz13.hot.corp.google.com with ESMTP id o984e277011763 for ; Thu, 7 Oct 2010 21:40:06 -0700 Received: by pxi5 with SMTP id 5so295350pxi.40 for ; Thu, 07 Oct 2010 21:40:02 -0700 (PDT) Date: Thu, 7 Oct 2010 21:39:56 -0700 From: Michel Lespinasse Subject: Re: [PATCH 2/3] Retry page fault when blocking on disk transfer. Message-ID: <20101008043956.GA25662@google.com> References: <1286265215-9025-1-git-send-email-walken@google.com> <1286265215-9025-3-git-send-email-walken@google.com> <4CAB628D.3030205@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Rik van Riel , Linus Torvalds Cc: linux-mm@kvack.org, Ying Han , linux-kernel@vger.kernel.org, Andrew Morton , Nick Piggin , Peter Zijlstra List-ID: On Tue, Oct 05, 2010 at 03:44:22PM -0700, Michel Lespinasse wrote: > On Tue, Oct 5, 2010 at 10:38 AM, Rik van Riel wrote: > > Looks like it should be relatively easy to do something > > similar in do_swap_page also. > > Good idea. We don't make use of swap too much, which is probably why > we didn't have that in our kernel, but it seems like a good idea just > for uniformity. I'll add this in a follow-on patch. So here's the patch. Sorry for the delay - it did not take long to write, but I couldn't test it before today. Please have a look - I'd like to add this to the series I sent earlier. ----------------------------------- 8< --------------------------------- Retry page fault when blocking on swap in This change is the cousin of 'Retry page fault when blocking on disk transfer'. The idea here is to reduce mmap_sem hold times that are caused by disk transfers when swapping in pages. We drop mmap_sem while waiting for the page lock, and return the VM_FAULT_RETRY flag. do_page_fault will then re-acquire mmap_sem and retry the page fault. It is expected that upon retry the page will now be cached, and thus the retry will complete with a low mmap_sem hold time. Signed-off-by: Michel Lespinasse diff --git a/mm/memory.c b/mm/memory.c index b068c68..0ec70b4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2613,6 +2613,21 @@ int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end) return 0; } +static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm, + unsigned int flags) +{ + if (trylock_page(page)) + return 1; + if (!(flags & FAULT_FLAG_ALLOW_RETRY)) { + __lock_page(page); + return 1; + } + + up_read(&mm->mmap_sem); + wait_on_page_locked(page); + return 0; +} + /* * We enter with non-exclusive mmap_sem (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -2626,6 +2641,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, struct page *page, *swapcache = NULL; swp_entry_t entry; pte_t pte; + int locked; struct mem_cgroup *ptr = NULL; int exclusive = 0; int ret = 0; @@ -2676,8 +2692,12 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out_release; } - lock_page(page); + locked = lock_page_or_retry(page, mm, flags); delayacct_clear_flag(DELAYACCT_PF_SWAPIN); + if (!locked) { + ret |= VM_FAULT_RETRY; + goto out_release; + } /* * Make sure try_to_free_swap or reuse_swap_page or swapoff did not -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- 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