Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755435Ab0K2Xj5 (ORCPT ); Mon, 29 Nov 2010 18:39:57 -0500 Received: from LUNGE.MIT.EDU ([18.54.1.69]:40097 "EHLO lunge.queued.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752687Ab0K2Xj4 (ORCPT ); Mon, 29 Nov 2010 18:39:56 -0500 Date: Mon, 29 Nov 2010 15:39:51 -0800 From: Andres Salomon To: Grant Likely Cc: "H. Peter Anvin" , Ingo Molnar , Milton Miller , devicetree-discuss@lists.ozlabs.org, Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH 3/3] x86: OLPC: speed up device tree creation during boot (v4) Message-ID: <20101129153951.74202a84@queued.net> In-Reply-To: <20101116221241.21419250@queued.net> References: <20101111214546.4e573cad@queued.net> <20101112002704.50c629e2@queued.net> <20101114095013.GB24206@elte.hu> <4CE0B54E.6000101@zytor.com> <20101115070254.GA25243@elte.hu> <4CE17133.2050101@zytor.com> <20101116221241.21419250@queued.net> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2339 Lines: 72 Calling alloc_bootmem() for tiny chunks of memory over and over is really slow; on an XO-1, it caused the time between when the kernel started booting and when the display came alive (post-lxfb probe) to increase to 44s. This patch optimizes the prom_early_alloc function by calling alloc_bootmem for 4k-sized blocks of memory, and handing out chunks of that to callers. With this patch, the time between kernel load and display initialization decreased to 23s. If there's a better way to do this early in the boot process, please let me know. (Note: increasing the chunk size to 16k didn't noticably affect boot time, and wasted 9k.) v4: clarify comment, requested by hpa v3: fix wasted memory buglet found by Milton Miller, and style fix. v2: reorder prom_early_alloc as suggested by Grant. Signed-off-by: Andres Salomon --- arch/x86/platform/olpc/olpc_dt.c | 28 +++++++++++++++++++++++----- 1 files changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/x86/platform/olpc/olpc_dt.c b/arch/x86/platform/olpc/olpc_dt.c index 7054697..dab8746 100644 --- a/arch/x86/platform/olpc/olpc_dt.c +++ b/arch/x86/platform/olpc/olpc_dt.c @@ -126,14 +126,32 @@ static unsigned int prom_early_allocated __initdata; void * __init prom_early_alloc(unsigned long size) { + static u8 *mem; + static size_t free_mem; void *res; - res = alloc_bootmem(size); - if (res) - memset(res, 0, size); - - prom_early_allocated += size; + if (free_mem < size) { + const size_t chunk_size = max(PAGE_SIZE, size); + + /* + * To mimimize the number of allocations, grab at least + * PAGE_SIZE of memory (that's an arbitrary choice that's + * fast enough on the platforms we care about while minimizing + * wasted bootmem) and hand off chunks of it to callers. + */ + res = alloc_bootmem(chunk_size); + if (!res) + return NULL; + prom_early_allocated += chunk_size; + memset(res, 0, chunk_size); + free_mem = chunk_size; + mem = res; + } + /* allocate from the local cache */ + free_mem -= size; + res = mem; + mem += size; return res; } -- 1.7.2.3 -- 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/