Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932269Ab3FQHNf (ORCPT ); Mon, 17 Jun 2013 03:13:35 -0400 Received: from lgeamrelo02.lge.com ([156.147.1.126]:47140 "EHLO LGEAMRELO02.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932162Ab3FQHNd (ORCPT ); Mon, 17 Jun 2013 03:13:33 -0400 X-AuditID: 9c93017e-b7cbcae00000388c-77-51beb71b8047 Date: Mon, 17 Jun 2013 16:13:31 +0900 From: Minchan Kim To: John Stultz Cc: LKML , Andrew Morton , Android Kernel Team , Robert Love , Mel Gorman , Hugh Dickins , Dave Hansen , Rik van Riel , Dmitry Adamushko , Dave Chinner , Neil Brown , Andrea Righi , Andrea Arcangeli , "Aneesh Kumar K.V" , Mike Hommey , Taras Glek , Dhaval Giani , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , "linux-mm@kvack.org" Subject: Re: [PATCH 7/8] vrange: Add method to purge volatile ranges Message-ID: <20130617071331.GA3251@bbox> References: <1371010971-15647-1-git-send-email-john.stultz@linaro.org> <1371010971-15647-8-git-send-email-john.stultz@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1371010971-15647-8-git-send-email-john.stultz@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4890 Lines: 140 Hello John, I am rewriting purging path and found a bug from this patch. I might forget it so I will send this comment for recording. On Tue, Jun 11, 2013 at 09:22:50PM -0700, John Stultz wrote: > From: Minchan Kim > > This patch adds discarding function to purge volatile ranges under > memory pressure. Logic is as following: > > 1. Memory pressure happens > 2. VM start to reclaim pages > 3. Check the page is in volatile range. > 4. If so, zap the page from the process's page table. > (By semantic vrange(2), we should mark it with another one to > make page fault when you try to access the address. It will > be introduced later patch) > 5. If page is unmapped from all processes, discard it instead of swapping. > > This patch does not address the case where there is no swap, which > keeps anonymous pages from being aged off the LRUs. Minchan has > additional patches that add support for purging anonymous pages > > XXX: First pass at file purging. Seems to work, but is likely broken > and needs close review. > > Cc: Andrew Morton > Cc: Android Kernel Team > Cc: Robert Love > Cc: Mel Gorman > Cc: Hugh Dickins > Cc: Dave Hansen > Cc: Rik van Riel > Cc: Dmitry Adamushko > Cc: Dave Chinner > Cc: Neil Brown > Cc: Andrea Righi > Cc: Andrea Arcangeli > Cc: Aneesh Kumar K.V > Cc: Mike Hommey > Cc: Taras Glek > Cc: Dhaval Giani > Cc: Jan Kara > Cc: KOSAKI Motohiro > Cc: Michel Lespinasse > Cc: Minchan Kim > Cc: linux-mm@kvack.org > Signed-off-by: Minchan Kim > [jstultz: Reworked to add purging of file pages, commit log tweaks] > Signed-off-by: John Stultz > --- > include/linux/rmap.h | 12 +- > include/linux/swap.h | 1 + > include/linux/vrange.h | 7 ++ > mm/ksm.c | 2 +- > mm/rmap.c | 30 +++-- > mm/swapfile.c | 36 ++++++ > mm/vmscan.c | 16 ++- > mm/vrange.c | 332 +++++++++++++++++++++++++++++++++++++++++++++++++ > 8 files changed, 420 insertions(+), 16 deletions(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 6dacb93..6432dfb 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -83,6 +83,8 @@ enum ttu_flags { > }; > < snip > > @@ -662,7 +663,7 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) > */ > int page_referenced_one(struct page *page, struct vm_area_struct *vma, > unsigned long address, unsigned int *mapcount, > - unsigned long *vm_flags) > + unsigned long *vm_flags, int *is_vrange) > { > struct mm_struct *mm = vma->vm_mm; > int referenced = 0; > @@ -724,6 +725,9 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma, > referenced++; > } > pte_unmap_unlock(pte, ptl); > + if (is_vrange && > + vrange_address(mm, address, address + PAGE_SIZE - 1)) > + *is_vrange = 1; < snip > > +static bool __vrange_address(struct vrange_root *vroot, > + unsigned long start, unsigned long end) > +{ > + struct interval_tree_node *node; > + > + node = interval_tree_iter_first(&vroot->v_rb, start, end); > + return node ? true : false; > +} > + > +bool vrange_address(struct mm_struct *mm, > + unsigned long start, unsigned long end) > +{ > + struct vrange_root *vroot; > + unsigned long vstart_idx, vend_idx; > + struct vm_area_struct *vma; > + bool ret; > + > + vma = find_vma(mm, start); It seems to be tweaked by you while you are refactoring with file-vrange The problem of the code is that you couldn't use vma without holding the lock of mmap_sem and you couldn't use the lock in purging path because you couldn't know other tasks's state so it might be a dealock if you try to hold a lock. > + if (vma->vm_file && (vma->vm_flags & VM_SHARED)) { > + vroot = &vma->vm_file->f_mapping->vroot; > + vstart_idx = vma->vm_pgoff + start - vma->vm_start; > + vend_idx = vma->vm_pgoff + end - vma->vm_start; > + } else { > + vroot = &mm->vroot; > + vstart_idx = start; > + vend_idx = end; > + } > + > + vrange_lock(vroot); > + ret = __vrange_address(vroot, vstart_idx, vend_idx); > + vrange_unlock(vroot); > + return ret; > +} > + -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/