![Andres Salomon](/assets/img/avatar_default.png)
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 <dilinger@queued.net> LKML-Reference: <20101129153951.74202a84@queued.net> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
184 lines
4 KiB
C
184 lines
4 KiB
C
/*
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* OLPC-specific OFW device tree support code.
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*
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* Paul Mackerras August 1996.
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* Copyright (C) 1996-2005 Paul Mackerras.
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*
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* Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
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* {engebret|bergner}@us.ibm.com
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*
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* Adapted for sparc by David S. Miller davem@davemloft.net
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* Adapted for x86/OLPC by Andres Salomon <dilinger@queued.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/bootmem.h>
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#include <linux/of.h>
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#include <linux/of_pdt.h>
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#include <asm/olpc_ofw.h>
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static phandle __init olpc_dt_getsibling(phandle node)
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{
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const void *args[] = { (void *)node };
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void *res[] = { &node };
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if ((s32)node == -1)
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return 0;
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if (olpc_ofw("peer", args, res) || (s32)node == -1)
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return 0;
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return node;
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}
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static phandle __init olpc_dt_getchild(phandle node)
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{
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const void *args[] = { (void *)node };
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void *res[] = { &node };
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if ((s32)node == -1)
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return 0;
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if (olpc_ofw("child", args, res) || (s32)node == -1) {
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pr_err("PROM: %s: fetching child failed!\n", __func__);
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return 0;
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}
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return node;
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}
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static int __init olpc_dt_getproplen(phandle node, const char *prop)
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{
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const void *args[] = { (void *)node, prop };
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int len;
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void *res[] = { &len };
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if ((s32)node == -1)
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return -1;
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if (olpc_ofw("getproplen", args, res)) {
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pr_err("PROM: %s: getproplen failed!\n", __func__);
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return -1;
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}
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return len;
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}
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static int __init olpc_dt_getproperty(phandle node, const char *prop,
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char *buf, int bufsize)
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{
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int plen;
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plen = olpc_dt_getproplen(node, prop);
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if (plen > bufsize || plen < 1) {
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return -1;
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} else {
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const void *args[] = { (void *)node, prop, buf, (void *)plen };
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void *res[] = { &plen };
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if (olpc_ofw("getprop", args, res)) {
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pr_err("PROM: %s: getprop failed!\n", __func__);
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return -1;
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}
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}
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return plen;
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}
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static int __init olpc_dt_nextprop(phandle node, char *prev, char *buf)
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{
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const void *args[] = { (void *)node, prev, buf };
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int success;
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void *res[] = { &success };
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buf[0] = '\0';
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if ((s32)node == -1)
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return -1;
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if (olpc_ofw("nextprop", args, res) || success != 1)
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return -1;
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return 0;
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}
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static int __init olpc_dt_pkg2path(phandle node, char *buf,
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const int buflen, int *len)
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{
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const void *args[] = { (void *)node, buf, (void *)buflen };
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void *res[] = { len };
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if ((s32)node == -1)
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return -1;
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if (olpc_ofw("package-to-path", args, res) || *len < 1)
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return -1;
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return 0;
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}
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static unsigned int prom_early_allocated __initdata;
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void * __init prom_early_alloc(unsigned long size)
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{
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static u8 *mem;
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static size_t free_mem;
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void *res;
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if (free_mem < size) {
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const size_t chunk_size = max(PAGE_SIZE, size);
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/*
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* To mimimize the number of allocations, grab at least
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* PAGE_SIZE of memory (that's an arbitrary choice that's
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* fast enough on the platforms we care about while minimizing
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* wasted bootmem) and hand off chunks of it to callers.
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*/
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res = alloc_bootmem(chunk_size);
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if (!res)
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return NULL;
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prom_early_allocated += chunk_size;
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memset(res, 0, chunk_size);
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free_mem = chunk_size;
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mem = res;
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}
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/* allocate from the local cache */
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free_mem -= size;
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res = mem;
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mem += size;
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return res;
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}
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static struct of_pdt_ops prom_olpc_ops __initdata = {
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.nextprop = olpc_dt_nextprop,
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.getproplen = olpc_dt_getproplen,
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.getproperty = olpc_dt_getproperty,
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.getchild = olpc_dt_getchild,
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.getsibling = olpc_dt_getsibling,
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.pkg2path = olpc_dt_pkg2path,
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};
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void __init olpc_dt_build_devicetree(void)
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{
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phandle root;
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if (!olpc_ofw_is_installed())
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return;
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root = olpc_dt_getsibling(0);
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if (!root) {
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pr_err("PROM: unable to get root node from OFW!\n");
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return;
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}
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of_pdt_build_devicetree(root, &prom_olpc_ops);
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pr_info("PROM DT: Built device tree with %u bytes of memory.\n",
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prom_early_allocated);
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}
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