forked from Minki/linux
xen: Fix selfballooning and ensure it doesn't go too far
The balloon driver's "current_pages" is very different from totalram_pages. Self-ballooning needs to be driven by the latter. Also, Committed_AS doesn't account for pages used by the kernel so: 1) Add totalreserve_pages to Committed_AS for the normal target. 2) Enforce a floor for when there are little or no user-space threads using memory (e.g. single-user mode) to avoid OOMs. The floor function includes a "min_usable_mb" tuneable in case we discover later that the floor function is still too aggressive in some workloads, though likely it will not be needed. Changes since version 4: - change floor calculation so that it is not as aggressive; this version uses a piecewise linear function similar to minimum_target in the 2.6.18 balloon driver, but modified to add to totalreserve_pages instead of subtract from max_pfn, the 2.6.18 version causes OOMs on recent kernels because the kernel has expanded over time - change safety_margin to min_usable_mb and comment on its use - since committed_as does NOT include kernel space (and other reserved pages), totalreserve_pages is now added to committed_as. The result is less aggressive self-ballooning, but theoretically more appropriate. Changes since version 3: - missing include causes compile problem when CONFIG_FRONTSWAP is disabled - add comments after includes Changes since version 2: - missing include causes compile problem only on 32-bit Changes since version 1: - tuneable safety margin added [v5: avi.miller@oracle.com: still too aggressive, seeing some OOMs] [v4: konrad.wilk@oracle.com: fix compile when CONFIG_FRONTSWAP is disabled] [v3: guru.anbalagane@oracle.com: fix 32-bit compile] [v2: konrad.wilk@oracle.com: make safety margin tuneable] Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com> [v1: Altered description and added an extra include] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Dan Magenheimer
Konrad Rzeszutek Wilk
parent
1f1503ba09
commit
38a1ed4f03
@ -68,6 +68,8 @@
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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/swap.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/workqueue.h>
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@ -92,6 +94,15 @@ static unsigned int selfballoon_uphysteresis __read_mostly = 1;
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/* In HZ, controls frequency of worker invocation. */
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static unsigned int selfballoon_interval __read_mostly = 5;
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/*
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* Minimum usable RAM in MB for selfballooning target for balloon.
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* If non-zero, it is added to totalreserve_pages and self-ballooning
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* will not balloon below the sum. If zero, a piecewise linear function
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* is calculated as a minimum and added to totalreserve_pages. Note that
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* setting this value indiscriminately may cause OOMs and crashes.
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*/
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static unsigned int selfballoon_min_usable_mb;
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static void selfballoon_process(struct work_struct *work);
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static DECLARE_DELAYED_WORK(selfballoon_worker, selfballoon_process);
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@ -188,20 +199,23 @@ static int __init xen_selfballooning_setup(char *s)
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__setup("selfballooning", xen_selfballooning_setup);
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#endif /* CONFIG_FRONTSWAP */
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#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
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/*
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* Use current balloon size, the goal (vm_committed_as), and hysteresis
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* parameters to set a new target balloon size
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*/
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static void selfballoon_process(struct work_struct *work)
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{
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unsigned long cur_pages, goal_pages, tgt_pages;
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unsigned long cur_pages, goal_pages, tgt_pages, floor_pages;
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unsigned long useful_pages;
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bool reset_timer = false;
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if (xen_selfballooning_enabled) {
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cur_pages = balloon_stats.current_pages;
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cur_pages = totalram_pages;
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tgt_pages = cur_pages; /* default is no change */
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goal_pages = percpu_counter_read_positive(&vm_committed_as) +
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balloon_stats.current_pages - totalram_pages;
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totalreserve_pages;
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#ifdef CONFIG_FRONTSWAP
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/* allow space for frontswap pages to be repatriated */
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if (frontswap_selfshrinking && frontswap_enabled)
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@ -216,7 +230,26 @@ static void selfballoon_process(struct work_struct *work)
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((goal_pages - cur_pages) /
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selfballoon_uphysteresis);
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/* else if cur_pages == goal_pages, no change */
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balloon_set_new_target(tgt_pages);
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useful_pages = max_pfn - totalreserve_pages;
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if (selfballoon_min_usable_mb != 0)
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floor_pages = totalreserve_pages +
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MB2PAGES(selfballoon_min_usable_mb);
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/* piecewise linear function ending in ~3% slope */
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else if (useful_pages < MB2PAGES(16))
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floor_pages = max_pfn; /* not worth ballooning */
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else if (useful_pages < MB2PAGES(64))
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floor_pages = totalreserve_pages + MB2PAGES(16) +
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((useful_pages - MB2PAGES(16)) >> 1);
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else if (useful_pages < MB2PAGES(512))
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floor_pages = totalreserve_pages + MB2PAGES(40) +
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((useful_pages - MB2PAGES(40)) >> 3);
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else /* useful_pages >= MB2PAGES(512) */
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floor_pages = totalreserve_pages + MB2PAGES(99) +
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((useful_pages - MB2PAGES(99)) >> 5);
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if (tgt_pages < floor_pages)
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tgt_pages = floor_pages;
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balloon_set_new_target(tgt_pages +
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balloon_stats.current_pages - totalram_pages);
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reset_timer = true;
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}
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#ifdef CONFIG_FRONTSWAP
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@ -339,6 +372,31 @@ static ssize_t store_selfballoon_uphys(struct sys_device *dev,
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static SYSDEV_ATTR(selfballoon_uphysteresis, S_IRUGO | S_IWUSR,
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show_selfballoon_uphys, store_selfballoon_uphys);
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SELFBALLOON_SHOW(selfballoon_min_usable_mb, "%d\n",
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selfballoon_min_usable_mb);
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static ssize_t store_selfballoon_min_usable_mb(struct sys_device *dev,
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struct sysdev_attribute *attr,
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const char *buf,
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size_t count)
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{
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unsigned long val;
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int err;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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err = strict_strtoul(buf, 10, &val);
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if (err || val == 0)
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return -EINVAL;
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selfballoon_min_usable_mb = val;
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return count;
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}
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static SYSDEV_ATTR(selfballoon_min_usable_mb, S_IRUGO | S_IWUSR,
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show_selfballoon_min_usable_mb,
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store_selfballoon_min_usable_mb);
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#ifdef CONFIG_FRONTSWAP
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SELFBALLOON_SHOW(frontswap_selfshrinking, "%d\n", frontswap_selfshrinking);
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@ -420,6 +478,7 @@ static struct attribute *selfballoon_attrs[] = {
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&attr_selfballoon_interval.attr,
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&attr_selfballoon_downhysteresis.attr,
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&attr_selfballoon_uphysteresis.attr,
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&attr_selfballoon_min_usable_mb.attr,
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#ifdef CONFIG_FRONTSWAP
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&attr_frontswap_selfshrinking.attr,
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&attr_frontswap_hysteresis.attr,
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