cmm.c

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/*
 * Collaborative memory management interface.
 *
 * Copyright (C) 2008 IBM Corporation
 * Author(s): Brian King ([email protected]),
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/oom.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/stringify.h>
#include <linux/swap.h>
#include <linux/device.h>
#include <asm/firmware.h>
#include <asm/hvcall.h>
#include <asm/mmu.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <linux/memory.h>

#include "plpar_wrappers.h"

#define CMM_DRIVER_VERSION  "1.0.0"
#define CMM_DEFAULT_DELAY   1
#define CMM_HOTPLUG_DELAY   5
#define CMM_DEBUG           0
#define CMM_DISABLE     0
#define CMM_OOM_KB      1024
#define CMM_MIN_MEM_MB      256
#define KB2PAGES(_p)        ((_p)>>(PAGE_SHIFT-10))
#define PAGES2KB(_p)        ((_p)<<(PAGE_SHIFT-10))
/*
 * The priority level tries to ensure that this notifier is called as
 * late as possible to reduce thrashing in the shared memory pool.
 */
#define CMM_MEM_HOTPLUG_PRI 1
#define CMM_MEM_ISOLATE_PRI 15

static unsigned int delay = CMM_DEFAULT_DELAY;
static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
static unsigned int oom_kb = CMM_OOM_KB;
static unsigned int cmm_debug = CMM_DEBUG;
static unsigned int cmm_disabled = CMM_DISABLE;
static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
static struct device cmm_dev;

MODULE_AUTHOR("Brian King <[email protected]>");
MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
MODULE_LICENSE("GPL");
MODULE_VERSION(CMM_DRIVER_VERSION);

module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
         "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove "
         "before loaning resumes. "
         "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
         "[Default=" __stringify(CMM_OOM_KB) "]");
module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
         "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
         "[Default=" __stringify(CMM_DEBUG) "]");

#define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long))

#define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }

struct cmm_page_array {
    struct cmm_page_array *next;
    unsigned long index;
    unsigned long page[CMM_NR_PAGES];
};

static unsigned long loaned_pages;
static unsigned long loaned_pages_target;
static unsigned long oom_freed_pages;

static struct cmm_page_array *cmm_page_list;
static DEFINE_SPINLOCK(cmm_lock);

static DEFINE_MUTEX(hotplug_mutex);
static int hotplug_occurred; /* protected by the hotplug mutex */

static struct task_struct *cmm_thread_ptr;

static long cmm_alloc_pages(long nr)
{
    struct cmm_page_array *pa, *npa;
    unsigned long addr;
    long rc;

    cmm_dbg("Begin request for %ld pages\n", nr);

    while (nr) {
        /* Exit if a hotplug operation is in progress or occurred */
        if (mutex_trylock(&hotplug_mutex)) {
            if (hotplug_occurred) {
                mutex_unlock(&hotplug_mutex);
                break;
            }
            mutex_unlock(&hotplug_mutex);
        } else {
            break;
        }

        addr = __get_free_page(GFP_NOIO | __GFP_NOWARN |
                       __GFP_NORETRY | __GFP_NOMEMALLOC);
        if (!addr)
            break;
        spin_lock(&cmm_lock);
        pa = cmm_page_list;
        if (!pa || pa->index >= CMM_NR_PAGES) {
            /* Need a new page for the page list. */
            spin_unlock(&cmm_lock);
            npa = (struct cmm_page_array *)__get_free_page(
                    GFP_NOIO | __GFP_NOWARN |
                    __GFP_NORETRY | __GFP_NOMEMALLOC);
            if (!npa) {
                pr_info("%s: Can not allocate new page list\n", __func__);
                free_page(addr);
                break;
            }
            spin_lock(&cmm_lock);
            pa = cmm_page_list;

            if (!pa || pa->index >= CMM_NR_PAGES) {
                npa->next = pa;
                npa->index = 0;
                pa = npa;
                cmm_page_list = pa;
            } else
                free_page((unsigned long) npa);
        }

        if ((rc = plpar_page_set_loaned(__pa(addr)))) {
            pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc);
            spin_unlock(&cmm_lock);
            free_page(addr);
            break;
        }

        pa->page[pa->index++] = addr;
        loaned_pages++;
        totalram_pages--;
        spin_unlock(&cmm_lock);
        nr--;
    }

    cmm_dbg("End request with %ld pages unfulfilled\n", nr);
    return nr;
}

static long cmm_free_pages(long nr)
{
    struct cmm_page_array *pa;
    unsigned long addr;

    cmm_dbg("Begin free of %ld pages.\n", nr);
    spin_lock(&cmm_lock);
    pa = cmm_page_list;
    while (nr) {
        if (!pa || pa->index <= 0)
            break;
        addr = pa->page[--pa->index];

        if (pa->index == 0) {
            pa = pa->next;
            free_page((unsigned long) cmm_page_list);
            cmm_page_list = pa;
        }

        plpar_page_set_active(__pa(addr));
        free_page(addr);
        loaned_pages--;
        nr--;
        totalram_pages++;
    }
    spin_unlock(&cmm_lock);
    cmm_dbg("End request with %ld pages unfulfilled\n", nr);
    return nr;
}

static int cmm_oom_notify(struct notifier_block *self,
              unsigned long dummy, void *parm)
{
    unsigned long *freed = parm;
    long nr = KB2PAGES(oom_kb);

    cmm_dbg("OOM processing started\n");
    nr = cmm_free_pages(nr);
    loaned_pages_target = loaned_pages;
    *freed += KB2PAGES(oom_kb) - nr;
    oom_freed_pages += KB2PAGES(oom_kb) - nr;
    cmm_dbg("OOM processing complete\n");
    return NOTIFY_OK;
}

static void cmm_get_mpp(void)
{
    int rc;
    struct hvcall_mpp_data mpp_data;
    signed long active_pages_target, page_loan_request, target;
    signed long total_pages = totalram_pages + loaned_pages;
    signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;

    rc = h_get_mpp(&mpp_data);

    if (rc != H_SUCCESS)
        return;

    page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE);
    target = page_loan_request + (signed long)loaned_pages;

    if (target < 0 || total_pages < min_mem_pages)
        target = 0;

    if (target > oom_freed_pages)
        target -= oom_freed_pages;
    else
        target = 0;

    active_pages_target = total_pages - target;

    if (min_mem_pages > active_pages_target)
        target = total_pages - min_mem_pages;

    if (target < 0)
        target = 0;

    loaned_pages_target = target;

    cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
        page_loan_request, loaned_pages, loaned_pages_target,
        oom_freed_pages, totalram_pages);
}

static struct notifier_block cmm_oom_nb = {
    .notifier_call = cmm_oom_notify
};

static int cmm_thread(void *dummy)
{
    unsigned long timeleft;

    while (1) {
        timeleft = msleep_interruptible(delay * 1000);

        if (kthread_should_stop() || timeleft)
            break;

        if (mutex_trylock(&hotplug_mutex)) {
            if (hotplug_occurred) {
                hotplug_occurred = 0;
                mutex_unlock(&hotplug_mutex);
                cmm_dbg("Hotplug operation has occurred, "
                        "loaning activity suspended "
                        "for %d seconds.\n",
                        hotplug_delay);
                timeleft = msleep_interruptible(hotplug_delay *
                        1000);
                if (kthread_should_stop() || timeleft)
                    break;
                continue;
            }
            mutex_unlock(&hotplug_mutex);
        } else {
            cmm_dbg("Hotplug operation in progress, activity "
                    "suspended\n");
            continue;
        }

        cmm_get_mpp();

        if (loaned_pages_target > loaned_pages) {
            if (cmm_alloc_pages(loaned_pages_target - loaned_pages))
                loaned_pages_target = loaned_pages;
        } else if (loaned_pages_target < loaned_pages)
            cmm_free_pages(loaned_pages - loaned_pages_target);
    }
    return 0;
}

#define CMM_SHOW(name, format, args...)         \
    static ssize_t show_##name(struct device *dev,  \
                   struct device_attribute *attr,   \
                   char *buf)           \
    {                           \
        return sprintf(buf, format, ##args);        \
    }                           \
    static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)

CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages));
CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));

static ssize_t show_oom_pages(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages));
}

static ssize_t store_oom_pages(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf, size_t count)
{
    unsigned long val = simple_strtoul (buf, NULL, 10);

    if (!capable(CAP_SYS_ADMIN))
        return -EPERM;
    if (val != 0)
        return -EBADMSG;

    oom_freed_pages = 0;
    return count;
}

static DEVICE_ATTR(oom_freed_kb, S_IWUSR | S_IRUGO,
           show_oom_pages, store_oom_pages);

static struct device_attribute *cmm_attrs[] = {
    &dev_attr_loaned_kb,
    &dev_attr_loaned_target_kb,
    &dev_attr_oom_freed_kb,
};

static struct bus_type cmm_subsys = {
    .name = "cmm",
    .dev_name = "cmm",
};

static int cmm_sysfs_register(struct device *dev)
{
    int i, rc;

    if ((rc = subsys_system_register(&cmm_subsys, NULL)))
        return rc;

    dev->id = 0;
    dev->bus = &cmm_subsys;

    if ((rc = device_register(dev)))
        goto subsys_unregister;

    for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
        if ((rc = device_create_file(dev, cmm_attrs[i])))
            goto fail;
    }

    return 0;

fail:
    while (--i >= 0)
        device_remove_file(dev, cmm_attrs[i]);
    device_unregister(dev);
subsys_unregister:
    bus_unregister(&cmm_subsys);
    return rc;
}

static void cmm_unregister_sysfs(struct device *dev)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
        device_remove_file(dev, cmm_attrs[i]);
    device_unregister(dev);
    bus_unregister(&cmm_subsys);
}

static int cmm_reboot_notifier(struct notifier_block *nb,
                   unsigned long action, void *unused)
{
    if (action == SYS_RESTART) {
        if (cmm_thread_ptr)
            kthread_stop(cmm_thread_ptr);
        cmm_thread_ptr = NULL;
        cmm_free_pages(loaned_pages);
    }
    return NOTIFY_DONE;
}

static struct notifier_block cmm_reboot_nb = {
    .notifier_call = cmm_reboot_notifier,
};

static unsigned long cmm_count_pages(void *arg)
{
    struct memory_isolate_notify *marg = arg;
    struct cmm_page_array *pa;
    unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn);
    unsigned long end = start + (marg->nr_pages << PAGE_SHIFT);
    unsigned long idx;

    spin_lock(&cmm_lock);
    pa = cmm_page_list;
    while (pa) {
        if ((unsigned long)pa >= start && (unsigned long)pa < end)
            marg->pages_found++;
        for (idx = 0; idx < pa->index; idx++)
            if (pa->page[idx] >= start && pa->page[idx] < end)
                marg->pages_found++;
        pa = pa->next;
    }
    spin_unlock(&cmm_lock);
    return 0;
}

static int cmm_memory_isolate_cb(struct notifier_block *self,
                 unsigned long action, void *arg)
{
    int ret = 0;

    if (action == MEM_ISOLATE_COUNT)
        ret = cmm_count_pages(arg);

    return notifier_from_errno(ret);
}

static struct notifier_block cmm_mem_isolate_nb = {
    .notifier_call = cmm_memory_isolate_cb,
    .priority = CMM_MEM_ISOLATE_PRI
};

static int cmm_mem_going_offline(void *arg)
{
    struct memory_notify *marg = arg;
    unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn);
    unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT);
    struct cmm_page_array *pa_curr, *pa_last, *npa;
    unsigned long idx;
    unsigned long freed = 0;

    cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).\n",
            start_page, marg->nr_pages);
    spin_lock(&cmm_lock);

    /* Search the page list for pages in the range to be offlined */
    pa_last = pa_curr = cmm_page_list;
    while (pa_curr) {
        for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) {
            if ((pa_curr->page[idx] < start_page) ||
                (pa_curr->page[idx] >= end_page))
                continue;

            plpar_page_set_active(__pa(pa_curr->page[idx]));
            free_page(pa_curr->page[idx]);
            freed++;
            loaned_pages--;
            totalram_pages++;
            pa_curr->page[idx] = pa_last->page[--pa_last->index];
            if (pa_last->index == 0) {
                if (pa_curr == pa_last)
                    pa_curr = pa_last->next;
                pa_last = pa_last->next;
                free_page((unsigned long)cmm_page_list);
                cmm_page_list = pa_last;
                continue;
            }
        }
        pa_curr = pa_curr->next;
    }

    /* Search for page list structures in the range to be offlined */
    pa_last = NULL;
    pa_curr = cmm_page_list;
    while (pa_curr) {
        if (((unsigned long)pa_curr >= start_page) &&
                ((unsigned long)pa_curr < end_page)) {
            npa = (struct cmm_page_array *)__get_free_page(
                    GFP_NOIO | __GFP_NOWARN |
                    __GFP_NORETRY | __GFP_NOMEMALLOC);
            if (!npa) {
                spin_unlock(&cmm_lock);
                cmm_dbg("Failed to allocate memory for list "
                        "management. Memory hotplug "
                        "failed.\n");
                return ENOMEM;
            }
            memcpy(npa, pa_curr, PAGE_SIZE);
            if (pa_curr == cmm_page_list)
                cmm_page_list = npa;
            if (pa_last)
                pa_last->next = npa;
            free_page((unsigned long) pa_curr);
            freed++;
            pa_curr = npa;
        }

        pa_last = pa_curr;
        pa_curr = pa_curr->next;
    }

    spin_unlock(&cmm_lock);
    cmm_dbg("Released %ld pages in the search range.\n", freed);

    return 0;
}

static int cmm_memory_cb(struct notifier_block *self,
            unsigned long action, void *arg)
{
    int ret = 0;

    switch (action) {
    case MEM_GOING_OFFLINE:
        mutex_lock(&hotplug_mutex);
        hotplug_occurred = 1;
        ret = cmm_mem_going_offline(arg);
        break;
    case MEM_OFFLINE:
    case MEM_CANCEL_OFFLINE:
        mutex_unlock(&hotplug_mutex);
        cmm_dbg("Memory offline operation complete.\n");
        break;
    case MEM_GOING_ONLINE:
    case MEM_ONLINE:
    case MEM_CANCEL_ONLINE:
        break;
    }

    return notifier_from_errno(ret);
}

static struct notifier_block cmm_mem_nb = {
    .notifier_call = cmm_memory_cb,
    .priority = CMM_MEM_HOTPLUG_PRI
};

static int cmm_init(void)
{
    int rc = -ENOMEM;

    if (!firmware_has_feature(FW_FEATURE_CMO))
        return -EOPNOTSUPP;

    if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0)
        return rc;

    if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
        goto out_oom_notifier;

    if ((rc = cmm_sysfs_register(&cmm_dev)))
        goto out_reboot_notifier;

    if (register_memory_notifier(&cmm_mem_nb) ||
        register_memory_isolate_notifier(&cmm_mem_isolate_nb))
        goto out_unregister_notifier;

    if (cmm_disabled)
        return rc;

    cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
    if (IS_ERR(cmm_thread_ptr)) {
        rc = PTR_ERR(cmm_thread_ptr);
        goto out_unregister_notifier;
    }

    return rc;

out_unregister_notifier:
    unregister_memory_notifier(&cmm_mem_nb);
    unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
    cmm_unregister_sysfs(&cmm_dev);
out_reboot_notifier:
    unregister_reboot_notifier(&cmm_reboot_nb);
out_oom_notifier:
    unregister_oom_notifier(&cmm_oom_nb);
    return rc;
}

static void cmm_exit(void)
{
    if (cmm_thread_ptr)
        kthread_stop(cmm_thread_ptr);
    unregister_oom_notifier(&cmm_oom_nb);
    unregister_reboot_notifier(&cmm_reboot_nb);
    unregister_memory_notifier(&cmm_mem_nb);
    unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
    cmm_free_pages(loaned_pages);
    cmm_unregister_sysfs(&cmm_dev);
}

static int cmm_set_disable(const char *val, struct kernel_param *kp)
{
    int disable = simple_strtoul(val, NULL, 10);

    if (disable != 0 && disable != 1)
        return -EINVAL;

    if (disable && !cmm_disabled) {
        if (cmm_thread_ptr)
            kthread_stop(cmm_thread_ptr);
        cmm_thread_ptr = NULL;
        cmm_free_pages(loaned_pages);
    } else if (!disable && cmm_disabled) {
        cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
        if (IS_ERR(cmm_thread_ptr))
            return PTR_ERR(cmm_thread_ptr);
    }

    cmm_disabled = disable;
    return 0;
}

module_param_call(disable, cmm_set_disable, param_get_uint,
          &cmm_disabled, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
         "[Default=" __stringify(CMM_DISABLE) "]");

module_init(cmm_init);
module_exit(cmm_exit);