From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andres Salomon Subject: [PATCH 3/3] x86: OLPC: speed up device tree creation during boot (v3) Date: Tue, 16 Nov 2010 22:12:41 -0800 Message-ID: <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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4CE17133.2050101-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Grant Likely Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Milton Miller , "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner List-Id: devicetree@vger.kernel.org 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.) v3: fix wasted memory buglet found by Milton Miller, and style fixes. v2: reorder prom_early_alloc as suggested by Grant Likely. 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..6614ec4 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 4k of + * memory (that's an arbitrary choice that matches PAGE_SIZE on + * the platforms we care about, and minimizes 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