From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id E6C4C6B00A4 for ; Sat, 9 May 2009 02:56:55 -0400 (EDT) Date: Sat, 9 May 2009 14:56:40 +0800 From: Wu Fengguang Subject: Re: [RFC][PATCH] vmscan: report vm_flags in page_referenced() Message-ID: <20090509065640.GA6487@localhost> References: <20090501123541.7983a8ae.akpm@linux-foundation.org> <20090503031539.GC5702@localhost> <1241432635.7620.4732.camel@twins> <20090507121101.GB20934@localhost> <20090507151039.GA2413@cmpxchg.org> <1241709466.11251.164.camel@twins> <20090508041700.GC8892@localhost> <28c262360905080509q333ec8acv2d2be69d99e1dfa3@mail.gmail.com> <20090508121549.GA17077@localhost> <28c262360905080701h366e071cv1560b09126cbc78c@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <28c262360905080701h366e071cv1560b09126cbc78c@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Peter Zijlstra , Johannes Weiner , Andrew Morton , Rik van Riel , "linux-kernel@vger.kernel.org" , "tytso@mit.edu" , "linux-mm@kvack.org" , Elladan , Nick Piggin , Christoph Lameter , KOSAKI Motohiro List-ID: On Fri, May 08, 2009 at 10:01:19PM +0800, Minchan Kim wrote: > On Fri, May 8, 2009 at 9:15 PM, Wu Fengguang wrote: > > On Fri, May 08, 2009 at 08:09:24PM +0800, Minchan Kim wrote: > >> On Fri, May 8, 2009 at 1:17 PM, Wu Fengguang wrote: > >> > On Thu, May 07, 2009 at 11:17:46PM +0800, Peter Zijlstra wrote: > >> >> On Thu, 2009-05-07 at 17:10 +0200, Johannes Weiner wrote: > >> >> > >> >> > > @@ -1269,8 +1270,15 @@ static void shrink_active_list(unsigned > >> >> > > > >> >> > > A A A A A /* page_referenced clears PageReferenced */ > >> >> > > A A A A A if (page_mapping_inuse(page) && > >> >> > > - A A A A A A page_referenced(page, 0, sc->mem_cgroup)) > >> >> > > + A A A A A A page_referenced(page, 0, sc->mem_cgroup)) { > >> >> > > + A A A A A A A A struct address_space *mapping = page_mapping(page); > >> >> > > + > >> >> > > A A A A A A A A A pgmoved++; > >> >> > > + A A A A A A A A if (mapping && test_bit(AS_EXEC, &mapping->flags)) { > >> >> > > + A A A A A A A A A A A A list_add(&page->lru, &l_active); > >> >> > > + A A A A A A A A A A A A continue; > >> >> > > + A A A A A A A A } > >> >> > > + A A A A } > >> >> > > >> >> > Since we walk the VMAs in page_referenced anyway, wouldn't it be > >> >> > better to check if one of them is executable? A This would even work > >> >> > for executable anon pages. A After all, there are applications that cow > >> >> > executable mappings (sbcl and other language environments that use an > >> >> > executable, run-time modified core image come to mind). > >> >> > >> >> Hmm, like provide a vm_flags mask along to page_referenced() to only > >> >> account matching vmas... seems like a sensible idea. > >> > > >> > Here is a quick patch for your opinions. Compile tested. > >> > > >> > With the added vm_flags reporting, the mlock=>unevictable logic can > >> > possibly be made more straightforward. > >> > > >> > Thanks, > >> > Fengguang > >> > --- > >> > vmscan: report vm_flags in page_referenced() > >> > > >> > This enables more informed reclaim heuristics, eg. to protect executable > >> > file pages more aggressively. > >> > > >> > Signed-off-by: Wu Fengguang > >> > --- > >> > A include/linux/rmap.h | A A 5 +++-- > >> > A mm/rmap.c A A A A A A | A 30 +++++++++++++++++++++--------- > >> > A mm/vmscan.c A A A A A | A A 7 +++++-- > >> > A 3 files changed, 29 insertions(+), 13 deletions(-) > >> > > >> > --- linux.orig/include/linux/rmap.h > >> > +++ linux/include/linux/rmap.h > >> > @@ -83,7 +83,8 @@ static inline void page_dup_rmap(struct > >> > A /* > >> > A * Called from mm/vmscan.c to handle paging out > >> > A */ > >> > -int page_referenced(struct page *, int is_locked, struct mem_cgroup *cnt); > >> > +int page_referenced(struct page *, int is_locked, > >> > + A A A A A A A A A A A struct mem_cgroup *cnt, unsigned long *vm_flags); > >> > A int try_to_unmap(struct page *, int ignore_refs); > >> > > >> > A /* > >> > @@ -128,7 +129,7 @@ int page_wrprotect(struct page *page, in > >> > A #define anon_vma_prepare(vma) A (0) > >> > A #define anon_vma_link(vma) A A do {} while (0) > >> > > >> > -#define page_referenced(page,l,cnt) TestClearPageReferenced(page) > >> > +#define page_referenced(page, locked, cnt, flags) TestClearPageReferenced(page) > >> > A #define try_to_unmap(page, refs) SWAP_FAIL > >> > > >> > A static inline int page_mkclean(struct page *page) > >> > --- linux.orig/mm/rmap.c > >> > +++ linux/mm/rmap.c > >> > @@ -333,7 +333,8 @@ static int page_mapped_in_vma(struct pag > >> > A * repeatedly from either page_referenced_anon or page_referenced_file. > >> > A */ > >> > A static int page_referenced_one(struct page *page, > >> > - A A A struct vm_area_struct *vma, unsigned int *mapcount) > >> > + A A A A A A A A A A A A A A A struct vm_area_struct *vma, > >> > + A A A A A A A A A A A A A A A unsigned int *mapcount) > >> > A { > >> > A A A A struct mm_struct *mm = vma->vm_mm; > >> > A A A A unsigned long address; > >> > @@ -385,7 +386,8 @@ out: > >> > A } > >> > > >> > A static int page_referenced_anon(struct page *page, > >> > - A A A A A A A A A A A A A A A struct mem_cgroup *mem_cont) > >> > + A A A A A A A A A A A A A A A struct mem_cgroup *mem_cont, > >> > + A A A A A A A A A A A A A A A unsigned long *vm_flags) > >> > A { > >> > A A A A unsigned int mapcount; > >> > A A A A struct anon_vma *anon_vma; > >> > @@ -406,6 +408,7 @@ static int page_referenced_anon(struct p > >> > A A A A A A A A if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) > >> > A A A A A A A A A A A A continue; > >> > A A A A A A A A referenced += page_referenced_one(page, vma, &mapcount); > >> > + A A A A A A A *vm_flags |= vma->vm_flags; > >> > >> Sometime this vma don't contain the anon page. > >> That's why we need page_check_address. > >> For such a case, wrong *vm_flag cause be harmful to reclaim. > >> It can be happen in your first class citizen patch, I think. > > > > Yes I'm aware of that - the VMA area covers that page, but have no pte > > actually installed for that page. That should be OK - the presentation > > of such VMA is a good indication of it being some executable text. > > > > Sorry but I can't understand your point. > > This is general interface but not only executable text. > Sometime, The information of vma which don't really have the page can > be passed to caller. Right. But if the caller don't care, why bother passing the vm_flags parameter down to page_referenced_one()? We can do that when there comes a need, otherwise it sounds more like unnecessary overheads. > ex) It can be happen by COW, mremap, non-linear mapping and so on. > but I am not sure. Hmm, this reminded me of the mlocked page protection logic in page_referenced_one(). Why shall the "if (vma->vm_flags & VM_LOCKED)" check be placed *after* the page_check_address() check? Is there a case that an *existing* page frame is not mapped to the VM_LOCKED vma? And why not to protect the page in such a case? > I doubt vm_flag information is useful. Me too :) I don't expect many of the other flags to be useful. Just that passing them out blindly could be more convenient than doing if (vma->vm_flags & PROT_EXEC) *vm_flags = PROT_EXEC; But I do suspect passing out VM_LOCKED could help somehow. Thanks, Fengguang -- 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