From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751709Ab1AJF4v (ORCPT ); Mon, 10 Jan 2011 00:56:51 -0500 Received: from gate.crashing.org ([63.228.1.57]:34427 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751009Ab1AJF4u (ORCPT ); Mon, 10 Jan 2011 00:56:50 -0500 Subject: Re: [PATCH] memblock: Don't adjust size in memblock_find_base() From: Benjamin Herrenschmidt To: Yinghai Lu Cc: Ingo Molnar , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , David Miller In-Reply-To: <4D277A8C.5010502@kernel.org> References: <4D1BD928.50701@zytor.com> <4D1BE615.4000700@zytor.com> <20101230090648.GB7306@elte.hu> <20101230102815.GA29822@elte.hu> <20101230103002.GA30020@elte.hu> <20110105134434.GA22816@elte.hu> <4D277A8C.5010502@kernel.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 10 Jan 2011 16:56:29 +1100 Message-ID: <1294638989.17779.296.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-01-07 at 12:41 -0800, Yinghai Lu wrote: > While applying patch to use memblock to find aperture for 64bit x86. > Ingo found system with 1g + force_iommu Please run that through DaveM. I seem to remember that he relies on the size alignment to ensure that a lot of tiny allocations get properly coalesced or he runs out of regions at boot time. A better option would be to use a fixed alignment, or sized based but with a max threshold such as PAGE_SIZE. Cheers, Ben. > > No AGP bridge found > > Node 0: aperture @ 38000000 size 32 MB > > Aperture pointing to e820 RAM. Ignoring. > > Your BIOS doesn't leave a aperture memory hole > > Please enable the IOMMU option in the BIOS setup > > This costs you 64 MB of RAM > > Cannot allocate aperture memory hole (0,65536K) > > the corresponding code: > addr = memblock_find_in_range(0, 1ULL<<32, aper_size, 512ULL<<20); > if (addr == MEMBLOCK_ERROR || addr + aper_size > 0xffffffff) { > printk(KERN_ERR > "Cannot allocate aperture memory hole (%lx,%uK)\n", > addr, aper_size>>10); > return 0; > } > memblock_x86_reserve_range(addr, addr + aper_size, "aperture64") > > it fails because memblock core code align the size with 512M. that could make > size way too big. > > So don't align the size in that case. > > actually __memblock_alloc_base, the another caller already align that before calling that function. > > BTW. x86 does not use __memblock_alloc_base... > > Signed-off-by: Yinghai Lu > > --- > mm/memblock.c | 2 -- > 1 file changed, 2 deletions(-) > > Index: linux-2.6/mm/memblock.c > =================================================================== > --- linux-2.6.orig/mm/memblock.c > +++ linux-2.6/mm/memblock.c > @@ -137,8 +137,6 @@ static phys_addr_t __init_memblock membl > > BUG_ON(0 == size); > > - size = memblock_align_up(size, align); > - > /* Pump up max_addr */ > if (end == MEMBLOCK_ALLOC_ACCESSIBLE) > end = memblock.current_limit; > -- > 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/