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Diffstat (limited to '')
| -rw-r--r-- | net/rds/page.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/net/rds/page.c b/net/rds/page.c new file mode 100644 index 000000000..7cc57e098 --- /dev/null +++ b/net/rds/page.c @@ -0,0 +1,167 @@ +/* + * Copyright (c) 2006 Oracle. All rights reserved. + * + * This software is available to you under a choice of one of two + * licenses. You may choose to be licensed under the terms of the GNU + * General Public License (GPL) Version 2, available from the file + * COPYING in the main directory of this source tree, or the + * OpenIB.org BSD license below: + * + * Redistribution and use in source and binary forms, with or + * without modification, are permitted provided that the following + * conditions are met: + * + * - Redistributions of source code must retain the above + * copyright notice, this list of conditions and the following + * disclaimer. + * + * - Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following + * disclaimer in the documentation and/or other materials + * provided with the distribution. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + * + */ +#include <linux/highmem.h> +#include <linux/gfp.h> +#include <linux/cpu.h> +#include <linux/export.h> + +#include "rds.h" + +struct rds_page_remainder { + struct page *r_page; + unsigned long r_offset; +}; + +static +DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders); + +/** + * rds_page_remainder_alloc - build up regions of a message. + * + * @scat: Scatter list for message + * @bytes: the number of bytes needed. + * @gfp: the waiting behaviour of the allocation + * + * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to + * kmap the pages, etc. + * + * If @bytes is at least a full page then this just returns a page from + * alloc_page(). + * + * If @bytes is a partial page then this stores the unused region of the + * page in a per-cpu structure. Future partial-page allocations may be + * satisfied from that cached region. This lets us waste less memory on + * small allocations with minimal complexity. It works because the transmit + * path passes read-only page regions down to devices. They hold a page + * reference until they are done with the region. + */ +int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes, + gfp_t gfp) +{ + struct rds_page_remainder *rem; + unsigned long flags; + struct page *page; + int ret; + + gfp |= __GFP_HIGHMEM; + + /* jump straight to allocation if we're trying for a huge page */ + if (bytes >= PAGE_SIZE) { + page = alloc_page(gfp); + if (!page) { + ret = -ENOMEM; + } else { + sg_set_page(scat, page, PAGE_SIZE, 0); + ret = 0; + } + goto out; + } + + rem = &per_cpu(rds_page_remainders, get_cpu()); + local_irq_save(flags); + + while (1) { + /* avoid a tiny region getting stuck by tossing it */ + if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) { + rds_stats_inc(s_page_remainder_miss); + __free_page(rem->r_page); + rem->r_page = NULL; + } + + /* hand out a fragment from the cached page */ + if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) { + sg_set_page(scat, rem->r_page, bytes, rem->r_offset); + get_page(sg_page(scat)); + + if (rem->r_offset != 0) + rds_stats_inc(s_page_remainder_hit); + + rem->r_offset += ALIGN(bytes, 8); + if (rem->r_offset >= PAGE_SIZE) { + __free_page(rem->r_page); + rem->r_page = NULL; + } + ret = 0; + break; + } + + /* alloc if there is nothing for us to use */ + local_irq_restore(flags); + put_cpu(); + + page = alloc_page(gfp); + + rem = &per_cpu(rds_page_remainders, get_cpu()); + local_irq_save(flags); + + if (!page) { + ret = -ENOMEM; + break; + } + + /* did someone race to fill the remainder before us? */ + if (rem->r_page) { + __free_page(page); + continue; + } + + /* otherwise install our page and loop around to alloc */ + rem->r_page = page; + rem->r_offset = 0; + } + + local_irq_restore(flags); + put_cpu(); +out: + rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret, + ret ? NULL : sg_page(scat), ret ? 0 : scat->offset, + ret ? 0 : scat->length); + return ret; +} +EXPORT_SYMBOL_GPL(rds_page_remainder_alloc); + +void rds_page_exit(void) +{ + unsigned int cpu; + + for_each_possible_cpu(cpu) { + struct rds_page_remainder *rem; + + rem = &per_cpu(rds_page_remainders, cpu); + rdsdebug("cpu %u\n", cpu); + + if (rem->r_page) + __free_page(rem->r_page); + rem->r_page = NULL; + } +} |