From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f50.google.com (mail-yh0-f50.google.com [209.85.213.50]) by kanga.kvack.org (Postfix) with ESMTP id D71716B0035 for ; Tue, 10 Dec 2013 10:46:48 -0500 (EST) Received: by mail-yh0-f50.google.com with SMTP id b6so3976325yha.9 for ; Tue, 10 Dec 2013 07:46:48 -0800 (PST) Received: from bear.ext.ti.com (bear.ext.ti.com. [192.94.94.41]) by mx.google.com with ESMTPS id t39si9133181yhp.250.2013.12.10.07.46.47 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 10 Dec 2013 07:46:47 -0800 (PST) Message-ID: <52A744DF.7060005@ti.com> Date: Tue, 10 Dec 2013 18:44:15 +0200 From: Grygorii Strashko MIME-Version: 1.0 Subject: Re: [PATCH v3 02/23] mm/memblock: debug: don't free reserved array if !ARCH_DISCARD_MEMBLOCK References: <1386625856-12942-1-git-send-email-santosh.shilimkar@ti.com> <1386625856-12942-3-git-send-email-santosh.shilimkar@ti.com> <20131209161134.e161ddfedf284f2052cad4a5@linux-foundation.org> In-Reply-To: <20131209161134.e161ddfedf284f2052cad4a5@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Santosh Shilimkar Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Yinghai Lu , Tejun Heo Hi Andrew, On 12/10/2013 02:11 AM, Andrew Morton wrote: > On Mon, 9 Dec 2013 16:50:35 -0500 Santosh Shilimkar wrote: > >> Now the Nobootmem allocator will always try to free memory allocated for >> reserved memory regions (free_low_memory_core_early()) without taking >> into to account current memblock debugging configuration >> (CONFIG_ARCH_DISCARD_MEMBLOCK and CONFIG_DEBUG_FS state). >> As result if: >> - CONFIG_DEBUG_FS defined >> - CONFIG_ARCH_DISCARD_MEMBLOCK not defined; >> - reserved memory regions array have been resized during boot >> >> then: >> - memory allocated for reserved memory regions array will be freed to >> buddy allocator; >> - debug_fs entry "sys/kernel/debug/memblock/reserved" will show garbage >> instead of state of memory reservations. like: >> 0: 0x98393bc0..0x9a393bbf >> 1: 0xff120000..0xff11ffff >> 2: 0x00000000..0xffffffff >> >> Hence, do not free memory allocated for reserved memory regions if >> defined(CONFIG_DEBUG_FS) && !defined(CONFIG_ARCH_DISCARD_MEMBLOCK). > > Alternatives: > > - disable /proc/sys/kernel/debug/memblock/reserved in this case > > - disable defined(CONFIG_DEBUG_FS) && > !defined(CONFIG_ARCH_DISCARD_MEMBLOCK) in Kconfig. Yes. But this is debug information and it's useful to have it. > > How much memory are we talking about here? If it's more than "very > little" then I think either of these would be better - most users will > value the extra memory over an accurate > /proc/sys/kernel/debug/memblock/reserved? > Sorry, I have no real statistic information and I hit this issue while testing this series by simulating huge amount of bootmem allocation during kernel boot. The real number of entries i saw on Keystone & OMAP boards is no more than ~20. Few digits below: - size of static reserved memory regions array is 2048 bytes - the size of array is doubled during each allocation Regards, -grygorii -- 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