Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754870AbZC1Mqb (ORCPT ); Sat, 28 Mar 2009 08:46:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752974AbZC1MqW (ORCPT ); Sat, 28 Mar 2009 08:46:22 -0400 Received: from casper.infradead.org ([85.118.1.10]:59302 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752362AbZC1MqV (ORCPT ); Sat, 28 Mar 2009 08:46:21 -0400 Subject: Re: [RFC] x86: gup_fast() batch limit (was: DRM lock ordering fix series) From: Peter Zijlstra To: Brice Goglin Cc: Eric Anholt , Andi Kleen , linux-kernel@vger.kernel.org, dri-devel@lists.sourceforge.net, Nick Piggin In-Reply-To: <1238242929.4039.706.camel@laptop> References: <1238017510-26784-1-git-send-email-eric@anholt.net> <87ocvnmhqx.fsf@basil.nowhere.org> <1238170767.8275.2397.camel@gaiman.anholt.net> <1238171805.8275.2434.camel@gaiman.anholt.net> <20090327181018.GC11935@one.firstfloor.org> <1238184629.625.44.camel@gaiman.anholt.net> <1238201922.4039.403.camel@laptop> <49CDE401.2020502@inria.fr> <1238237283.4039.605.camel@laptop> <1238242929.4039.706.camel@laptop> Content-Type: text/plain Date: Sat, 28 Mar 2009 13:46:14 +0100 Message-Id: <1238244374.4039.743.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3232 Lines: 111 On Sat, 2009-03-28 at 13:22 +0100, Peter Zijlstra wrote: > I'm not really trusting my brain today, but something like the below > should work I think. > > Nick, any thoughts? > > Not-Signed-off-by: Peter Zijlstra > --- > arch/x86/mm/gup.c | 24 +++++++++++++++++++++--- > 1 files changed, 21 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c > index be54176..4ded5c3 100644 > --- a/arch/x86/mm/gup.c > +++ b/arch/x86/mm/gup.c > @@ -11,6 +11,8 @@ > > #include > > +#define GUP_BATCH 32 > + > static inline pte_t gup_get_pte(pte_t *ptep) > { > #ifndef CONFIG_X86_PAE > @@ -91,7 +93,8 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, > get_page(page); > pages[*nr] = page; > (*nr)++; > - > + if (*nr > GUP_BATCH) > + break; > } while (ptep++, addr += PAGE_SIZE, addr != end); > pte_unmap(ptep - 1); > > @@ -157,6 +160,8 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, > if (!gup_pte_range(pmd, addr, next, write, pages, nr)) > return 0; > } > + if (*nr > GUP_BATCH) > + break; > } while (pmdp++, addr = next, addr != end); > > return 1; > @@ -214,6 +219,8 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, > if (!gup_pmd_range(pud, addr, next, write, pages, nr)) > return 0; > } > + if (*nr > GUP_BATCH) > + break; > } while (pudp++, addr = next, addr != end); > > return 1; > @@ -226,7 +233,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, > unsigned long addr, len, end; > unsigned long next; > pgd_t *pgdp; > - int nr = 0; > + int batch = 0, nr = 0; > > start &= PAGE_MASK; > addr = start; > @@ -254,6 +261,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, > * (which we do on x86, with the above PAE exception), we can follow the > * address down to the the page and take a ref on it. > */ > +again: > local_irq_disable(); > pgdp = pgd_offset(mm, addr); > do { > @@ -262,11 +270,21 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, > next = pgd_addr_end(addr, end); > if (pgd_none(pgd)) > goto slow; > - if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) > + if (!gup_pud_range(pgd, addr, next, write, pages, &batch)) > goto slow; > + if (batch > GUP_BATCH) { > + local_irq_enable(); > + addr += batch << PAGE_SHIFT; > + nr += batch; > + batch = 0; > + if (addr != end) > + goto again; > + } > } while (pgdp++, addr = next, addr != end); > local_irq_enable(); > > + nr += batch; > + > VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); > return nr; > Would also need the following bit: @@ -274,6 +292,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, int ret; slow: + nr += batch; local_irq_enable(); slow_irqon: /* Try to get the remaining pages with get_user_pages */ -- 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/