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Message-ID: <20070604225714.GM20299@havoc.gtf.org>
Date: Mon, 4 Jun 2007 18:57:14 -0400
From: Jeff Garzik <jeff@...zik.org>
To: anil.s.keshavamurthy@...el.com
Cc: linux-kernel@...r.kernel.org, akpm@...l.org, ak@...e.de,
gregkh@...e.de, muli@...ibm.com, asit.k.mallick@...el.com,
suresh.b.siddha@...el.com, arjan@...ux.intel.com,
ashok.raj@...el.com, shaohua.li@...el.com, davem@...emloft.net
Subject: Re: [Intel-IOMMU 02/10] Library routines for handling pre-allocated pool of objects
On Mon, Jun 04, 2007 at 02:02:44PM -0700, anil.s.keshavamurthy@...el.com wrote:
> This patch provides a common interface for pre allocating and
> managing pool of objects.
>
> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> ---
> include/linux/respool.h | 43 +++++++++++
> lib/Makefile | 1
> lib/respool.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 220 insertions(+)
>
> Index: linux-2.6.22-rc3/include/linux/respool.h
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.22-rc3/include/linux/respool.h 2007-06-04 12:36:17.000000000 -0700
> @@ -0,0 +1,43 @@
> +/*
> + * respool.c - library routines for handling generic pre-allocated pool of objects
> + *
> + * Copyright (c) 2006, Intel Corporation.
> + *
> + * This file is released under the GPLv2.
> + *
> + * Copyright (C) 2006 Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> + *
> + */
> +
> +#ifndef _RESPOOL_H_
> +#define _RESPOOL_H_
> +
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +
> +typedef void *(*rpool_alloc_t)(unsigned int, gfp_t);
> +typedef void (*rpool_free_t)(void *, unsigned int);
> +
> +struct resource_pool {
> + struct work_struct work;
> + spinlock_t pool_lock; /* pool lock to walk the pool_head */
> + struct list_head pool_head; /* pool objects list head */
> + unsigned int min_count; /* min count to maintain */
> + unsigned int grow_count; /* grow by count when time to grow */
> + unsigned int curr_count; /* count of current free objects */
> + unsigned int alloc_size; /* objects size */
> + rpool_alloc_t alloc_mem; /* pool mem alloc function pointer */
> + rpool_free_t free_mem; /* pool mem free function pointer */
> +};
> +
> +void *get_resource_pool_obj(struct resource_pool *ppool);
> +void put_resource_pool_obj(void * vaddr, struct resource_pool *ppool);
> +void destroy_resource_pool(struct resource_pool *ppool);
> +int init_resource_pool(struct resource_pool *res,
> + unsigned int min_count, unsigned int alloc_size,
> + unsigned int grow_count, rpool_alloc_t alloc_fn,
> + rpool_free_t free_fn);
> +
> +#endif
> Index: linux-2.6.22-rc3/lib/Makefile
> ===================================================================
> --- linux-2.6.22-rc3.orig/lib/Makefile 2007-06-04 12:28:10.000000000 -0700
> +++ linux-2.6.22-rc3/lib/Makefile 2007-06-04 12:36:17.000000000 -0700
> @@ -58,6 +58,7 @@
> obj-$(CONFIG_AUDIT_GENERIC) += audit.o
>
> obj-$(CONFIG_SWIOTLB) += swiotlb.o
> +obj-$(CONFIG_DMAR) += respool.o
> obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
>
> lib-$(CONFIG_GENERIC_BUG) += bug.o
> Index: linux-2.6.22-rc3/lib/respool.c
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.22-rc3/lib/respool.c 2007-06-04 12:36:17.000000000 -0700
> @@ -0,0 +1,176 @@
> +/*
> + * respool.c - library routines for handling generic pre-allocated pool of objects
> + *
> + * Copyright (c) 2006, Intel Corporation.
> + *
> + * This file is released under the GPLv2.
> + *
> + * Copyright (C) 2006 Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> + */
> +
> +#include <linux/respool.h>
> +
> +/**
> + * get_resource_pool_obj - gets an object from the pool
> + * @ppool - resource pool in question
> + * This function gets an object from the pool and
> + * if the pool count drops below min_count, this
> + * function schedules work to grow the pool. If
> + * no elements are fount in the pool then this function
> + * tries to get memory from kernel.
> + */
> +void * get_resource_pool_obj(struct resource_pool *ppool)
> +{
> + unsigned long flags;
> + struct list_head *plist;
> + bool queue_work = 0;
> +
> + spin_lock_irqsave(&ppool->pool_lock, flags);
> + if (!list_empty(&ppool->pool_head)) {
> + plist = ppool->pool_head.next;
> + list_del(plist);
> + ppool->curr_count--;
> + } else {
> + /*Making sure that curr_count is 0 when list is empty */
> + plist = NULL;
> + BUG_ON(ppool->curr_count != 0);
> + }
> +
> + /* Check if pool needs to grow */
> + if (ppool->curr_count <= ppool->min_count)
> + queue_work = 1;
> + spin_unlock_irqrestore(&ppool->pool_lock, flags);
> +
> + if (queue_work)
> + schedule_work(&ppool->work); /* queue work to grow the pool */
> +
> +
> + if (plist) {
> + memset(plist, 0, ppool->alloc_size); /* Zero out memory */
> + return plist;
> + }
> +
> + /* Out of luck, try to get memory from kernel */
> + plist = (struct list_head *)ppool->alloc_mem(ppool->alloc_size,
> + GFP_ATOMIC);
Since you are outside the lock, you should pass in gfp_flags, to enhance
the chance of being able to use GFP_KERNEL in certain contexts.
> + return plist;
> +}
> +
> +/**
> + * put_resource_pool_obj - puts an object back to the pool
> + * @vaddr - object's address
> + * @ppool - resource pool in question.
> + * This function puts an object back to the pool.
> + */
> +void put_resource_pool_obj(void * vaddr, struct resource_pool *ppool)
> +{
> + unsigned long flags;
> + struct list_head *plist = (struct list_head *)vaddr;
> +
> + BUG_ON(!vaddr);
> + BUG_ON(!ppool);
> +
> + spin_lock_irqsave(&ppool->pool_lock, flags);
> + list_add(plist, &ppool->pool_head);
> + ppool->curr_count++;
> + spin_unlock_irqrestore(&ppool->pool_lock, flags);
you should add logic to free resources here (or queue_work to free the
resources), if the pool grows beyond a certain size.
> +/**
> + * grow_resource_pool - grows the given resource pool
> + * @work - work struct
> + * This functions gets the resource pool pointer from the
> + * work struct and grows the resource pool by grow_count.
> + */
> +static void
> +grow_resource_pool(struct work_struct * work)
> +{
> + struct resource_pool *ppool;
> + struct list_head *plist;
> + unsigned int min_count, grow_count = 0;
> + unsigned long flags;
> +
> + ppool = container_of(work, struct resource_pool, work);
> +
> + /* compute the minimum count to grow */
> + spin_lock_irqsave(&ppool->pool_lock, flags);
> + min_count = ppool->min_count + ppool->grow_count;
> + if (ppool->curr_count < min_count)
> + grow_count = min_count - ppool->curr_count;
> + spin_unlock_irqrestore(&ppool->pool_lock, flags);
> +
> + while(grow_count) {
> + plist = (struct list_head *)ppool->alloc_mem(ppool->alloc_size,
> + GFP_KERNEL);
> +
> + if (!plist)
> + break;
> +
> + /* Add the element to the list */
> + spin_lock_irqsave(&ppool->pool_lock, flags);
> + list_add(plist, &ppool->pool_head);
> + ppool->curr_count++;
> + spin_unlock_irqrestore(&ppool->pool_lock, flags);
> + grow_count--;
> + }
> +}
> +
> +/**
> + * destroy_resource_pool - destroys the given resource pool
> + * @ppool - resource pool in question.
> + * This function walks throuhg its list and frees up the
> + * preallocated objects.
> + */
> +void
> +destroy_resource_pool(struct resource_pool *ppool)
> +{
> + unsigned long flags;
> + struct list_head *plist;
> +
> + spin_lock_irqsave(&ppool->pool_lock, flags);
> + while (!list_empty(&ppool->pool_head)) {
> + plist = &ppool->pool_head;
> + list_del(plist);
> +
> + ppool->free_mem(plist, ppool->alloc_size);
> +
> + }
> + ppool->curr_count = 0;
> + spin_unlock_irqrestore(&ppool->pool_lock, flags);
> +}
> +
> +/**
> + * init_resource_pool - initializes the resource pool
> + * @res: resource pool in question.
> + * @min_count: count of objectes to pre-allocate
> + * @alloc_size: size of each objects
> + * @grow_count: count of objects to grow when required
> + * @alloc_fn: function which allocates memory
> + * @free_fn: function which frees memory
> + *
> + * This function initializes the given resource pool and
> + * populates the min_count of objects to begin with.
> + */
> +int
> +init_resource_pool(struct resource_pool *res,
> + unsigned int min_count, unsigned int alloc_size,
> + unsigned int grow_count, rpool_alloc_t alloc_fn,
> + rpool_free_t free_fn)
> +{
> + res->min_count = min_count;
> + res->alloc_size = alloc_size;
> + res->grow_count = grow_count;
> + res->curr_count = 0;
> + res->alloc_mem = alloc_fn;
> + res->free_mem = free_fn;
> + spin_lock_init(&res->pool_lock);
> + INIT_LIST_HEAD(&res->pool_head);
> + INIT_WORK(&res->work, grow_resource_pool);
> +
> + /* grow the pool */
> + grow_resource_pool(&res->work);
> +
> + return (res->curr_count == 0);
> +}
> +
>
> --
> -
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