Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932Ab0BLJCV (ORCPT ); Fri, 12 Feb 2010 04:02:21 -0500 Received: from ozlabs.org ([203.10.76.45]:56228 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750931Ab0BLJCT (ORCPT ); Fri, 12 Feb 2010 04:02:19 -0500 From: Michael Neuling To: KOSAKI Motohiro cc: Andrew Morton , Helge Deller , Americo Wang , Anton Blanchard , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Create initial stack independent of PAGE_SIZE In-reply-to: <20100212161305.73B2.A69D9226@jp.fujitsu.com> References: <20100209132529.bfc455b7.akpm@linux-foundation.org> <31586.1265953455@neuling.org> <20100212161305.73B2.A69D9226@jp.fujitsu.com> Comments: In-reply-to KOSAKI Motohiro message dated "Fri, 12 Feb 2010 16:20:40 +0900." X-Mailer: MH-E 8.2; nmh 1.3; GNU Emacs 23.1.1 Date: Fri, 12 Feb 2010 20:02:16 +1100 Message-ID: <2593.1265965336@neuling.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2478 Lines: 74 In message <20100212161305.73B2.A69D9226@jp.fujitsu.com> you wrote: > > Currently we create the initial stack based on the PAGE_SIZE. This is > > unnecessary. > > I don't think this is enough explanation. In past mail, you described > why page size dependency is harmful. I hope you add it into the patch > description. I don't think it's harmful, it's just irrelevant. Stack size is independent of page size. > IOW, we don't need to change the unnecessary-but-non-harmful behavior. > > > > > This creates this initial stack independent of the PAGE_SIZE. > > > > It also bumps up the number of 4k pages allocated from 20 to 32, to > > align with 64K page systems. > > Why do we need page-aligning? Do you mean this code doesn't works on > 128K (or more larger) page systems? If the "random" setting is not a common multiple of the 4k and 64k pages, they will end up getting aligned differently, hence causing what we are trying to avoid in the first place with this patch. I should probably add this as a comment in the code comment? Mikey > > > > > > Signed-off-by: Michael Neuling > > --- > > This is the second half of my original patch. This can be targeted for > > 2.6.34 as it's just a cleanup. > > > > Tested on PPC64 with 4k and 64k pages. > > > > fs/exec.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > Index: linux-2.6-ozlabs/fs/exec.c > > =================================================================== > > --- linux-2.6-ozlabs.orig/fs/exec.c > > +++ linux-2.6-ozlabs/fs/exec.c > > @@ -554,8 +554,6 @@ static int shift_arg_pages(struct vm_are > > return 0; > > } > > > > -#define EXTRA_STACK_VM_PAGES 20 /* random */ > > - > > /* > > * Finalizes the stack vm_area_struct. The flags and permissions are updat ed, > > * the stack is optionally relocated, and some extra space is added. > > @@ -630,7 +628,7 @@ int setup_arg_pages(struct linux_binprm > > goto out_unlock; > > } > > > > - stack_expand = EXTRA_STACK_VM_PAGES * PAGE_SIZE; > > + stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ > > stack_size = vma->vm_end - vma->vm_start; > > /* > > * Align this down to a page boundary as expand_stack > > > -- 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/