From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f44.google.com (mail-wg0-f44.google.com [74.125.82.44]) by kanga.kvack.org (Postfix) with ESMTP id 960AF6B007B for ; Mon, 17 Mar 2014 05:39:41 -0400 (EDT) Received: by mail-wg0-f44.google.com with SMTP id m15so4264266wgh.15 for ; Mon, 17 Mar 2014 02:39:40 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id oy1si4852306wjb.123.2014.03.17.02.39.39 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 17 Mar 2014 02:39:39 -0700 (PDT) Date: Mon, 17 Mar 2014 10:39:37 +0100 From: Jan Kara Subject: Re: [PATCH 2/3] vrange: Add purged page detection on setting memory non-volatile Message-ID: <20140317093937.GB2210@quack.suse.cz> References: <1394822013-23804-1-git-send-email-john.stultz@linaro.org> <1394822013-23804-3-git-send-email-john.stultz@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1394822013-23804-3-git-send-email-john.stultz@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: John Stultz Cc: LKML , Andrew Morton , Android Kernel Team , Johannes Weiner , Robert Love , Mel Gorman , Hugh Dickins , Dave Hansen , Rik van Riel , Dmitry Adamushko , Neil Brown , Andrea Arcangeli , Mike Hommey , Taras Glek , Dhaval Giani , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , Minchan Kim , "linux-mm@kvack.org" On Fri 14-03-14 11:33:32, John Stultz wrote: > Users of volatile ranges will need to know if memory was discarded. > This patch adds the purged state tracking required to inform userland > when it marks memory as non-volatile that some memory in that range > was purged and needs to be regenerated. > > This simplified implementation which uses some of the logic from > Minchan's earlier efforts, so credit to Minchan for his work. Some minor comments below... > > Cc: Andrew Morton > Cc: Android Kernel Team > Cc: Johannes Weiner > Cc: Robert Love > Cc: Mel Gorman > Cc: Hugh Dickins > Cc: Dave Hansen > Cc: Rik van Riel > Cc: Dmitry Adamushko > Cc: Neil Brown > Cc: Andrea Arcangeli > 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: John Stultz > --- > include/linux/swap.h | 15 +++++++++++-- > include/linux/vrange.h | 13 ++++++++++++ > mm/vrange.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 83 insertions(+), 2 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 46ba0c6..18c12f9 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -70,8 +70,19 @@ static inline int current_is_kswapd(void) > #define SWP_HWPOISON_NUM 0 > #endif > > -#define MAX_SWAPFILES \ > - ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM) > + > +/* > + * Purged volatile range pages > + */ > +#define SWP_VRANGE_PURGED_NUM 1 > +#define SWP_VRANGE_PURGED (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM) > + > + > +#define MAX_SWAPFILES ((1 << MAX_SWAPFILES_SHIFT) \ > + - SWP_MIGRATION_NUM \ > + - SWP_HWPOISON_NUM \ > + - SWP_VRANGE_PURGED_NUM \ > + ) > > /* > * Magic header for a swap area. The first part of the union is > diff --git a/include/linux/vrange.h b/include/linux/vrange.h > index 652396b..c4a1616 100644 > --- a/include/linux/vrange.h > +++ b/include/linux/vrange.h > @@ -1,7 +1,20 @@ > #ifndef _LINUX_VRANGE_H > #define _LINUX_VRANGE_H > > +#include > +#include > + > #define VRANGE_NONVOLATILE 0 > #define VRANGE_VOLATILE 1 > > +static inline swp_entry_t swp_entry_mk_vrange_purged(void) > +{ > + return swp_entry(SWP_VRANGE_PURGED, 0); > +} > + > +static inline int entry_is_vrange_purged(swp_entry_t entry) > +{ > + return swp_type(entry) == SWP_VRANGE_PURGED; > +} > + > #endif /* _LINUX_VRANGE_H */ > diff --git a/mm/vrange.c b/mm/vrange.c > index acb4356..844571b 100644 > --- a/mm/vrange.c > +++ b/mm/vrange.c > @@ -8,6 +8,60 @@ > #include > #include "internal.h" > > +struct vrange_walker { > + struct vm_area_struct *vma; > + int pages_purged; Maybe call this 'was_page_purged'? To better suggest the value is bool and not a number of pages... Or make that 'bool' instead of 'int'? > +}; > + > +static int vrange_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > + struct mm_walk *walk) > +{ > + struct vrange_walker *vw = walk->private; > + pte_t *pte; > + spinlock_t *ptl; > + > + if (pmd_trans_huge(*pmd)) > + return 0; > + if (pmd_trans_unstable(pmd)) > + return 0; > + > + pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > + for (; addr != end; pte++, addr += PAGE_SIZE) { > + if (!pte_present(*pte)) { > + swp_entry_t vrange_entry = pte_to_swp_entry(*pte); > + > + if (unlikely(entry_is_vrange_purged(vrange_entry))) { > + vw->pages_purged = 1; > + break; > + } > + } > + } > + pte_unmap_unlock(pte - 1, ptl); > + cond_resched(); > + > + return 0; > +} > + > +static unsigned long vrange_check_purged(struct mm_struct *mm, What's the point of this function returning ulong when everything else expects 'int'? > + struct vm_area_struct *vma, > + unsigned long start, > + unsigned long end) > +{ > + struct vrange_walker vw; > + struct mm_walk vrange_walk = { > + .pmd_entry = vrange_pte_range, > + .mm = vma->vm_mm, > + .private = &vw, > + }; > + vw.pages_purged = 0; > + vw.vma = vma; > + > + walk_page_range(start, end, &vrange_walk); > + > + return vw.pages_purged; > + > +} > + > static ssize_t do_vrange(struct mm_struct *mm, unsigned long start, > unsigned long end, int mode, int *purged) > { > @@ -57,6 +111,9 @@ static ssize_t do_vrange(struct mm_struct *mm, unsigned long start, > break; > case VRANGE_NONVOLATILE: > new_flags &= ~VM_VOLATILE; > + lpurged |= vrange_check_purged(mm, vma, > + vma->vm_start, > + vma->vm_end); Hum, why don't you actually just call vrange_check_purge() once for the whole syscall range? walk_page_range() seems to handle multiple vmas just fine... > } > > pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); > -- > 1.8.3.2 > Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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