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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH R3 7/7] xen/balloon: Memory hotplug support for Xen balloon driver
On Thu, Feb 03, 2011 at 05:30:33PM +0100, Daniel Kiper wrote:
> Features and fixes:
> - new version of memory hotplug patch which supports
> among others memory allocation policies during errors
> (try until success or stop at first error),
> - this version of patch was tested with tmem
> (selfballooning and frontswap) and works
> very well with it,
> - some other minor fixes.
>
> Signed-off-by: Daniel Kiper <dkiper@xxxxxxxxxxxx>
> ---
> drivers/xen/Kconfig | 10 ++
> drivers/xen/balloon.c | 231
> ++++++++++++++++++++++++++++++++++++++++++++++---
> 2 files changed, 230 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index 07bec09..8f880aa 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -9,6 +9,16 @@ config XEN_BALLOON
> the system to expand the domain's memory allocation, or alternatively
> return unneeded memory to the system.
>
> +config XEN_BALLOON_MEMORY_HOTPLUG
> + bool "Memory hotplug support for Xen balloon driver"
> + default n
> + depends on XEN_BALLOON && MEMORY_HOTPLUG
> + help
> + Memory hotplug support for Xen balloon driver allows expanding memory
> + available for the system above limit declared at system startup.
> + It is very useful on critical systems which require long
> + run without rebooting.
> +
> config XEN_SCRUB_PAGES
> bool "Scrub pages before returning them to system"
> depends on XEN_BALLOON
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index b1e199c..e43e928 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -6,6 +6,12 @@
> * Copyright (c) 2003, B Dragovic
> * Copyright (c) 2003-2004, M Williamson, K Fraser
> * Copyright (c) 2005 Dan M. Smith, IBM Corporation
> + * Copyright (c) 2010 Daniel Kiper
> + *
> + * Memory hotplug support was written by Daniel Kiper. Work on
> + * it was sponsored by Google under Google Summer of Code 2010
> + * program. Jeremy Fitzhardinge from Xen.org was the mentor for
> + * this project.
> *
> * This program is free software; you can redistribute it and/or
> * modify it under the terms of the GNU General Public License version 2
> @@ -44,6 +50,7 @@
> #include <linux/list.h>
> #include <linux/sysdev.h>
> #include <linux/gfp.h>
> +#include <linux/memory.h>
>
> #include <asm/page.h>
> #include <asm/pgalloc.h>
> @@ -80,6 +87,9 @@ enum bp_state {
> BP_HUNGRY
> };
>
> +#define MH_POLICY_TRY_UNTIL_SUCCESS 0
> +#define MH_POLICY_STOP_AT_FIRST_ERROR 1
Cool.
> +
> struct balloon_stats {
> /* We aim for 'current allocation' == 'target allocation'. */
> unsigned long current_pages;
> @@ -89,6 +99,10 @@ struct balloon_stats {
> unsigned long balloon_high;
> unsigned long schedule_delay;
> unsigned long max_schedule_delay;
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + unsigned long boot_max_pfn;
> + unsigned long mh_policy;
> +#endif
> };
>
> static DEFINE_MUTEX(balloon_mutex);
> @@ -206,18 +220,199 @@ static void update_schedule_delay(enum bp_state state)
> balloon_stats.schedule_delay = new_schedule_delay;
> }
>
> -static unsigned long current_target(void)
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> +static struct resource *allocate_memory_resource(unsigned long nr_pages)
> +{
> + resource_size_t r_min, r_size;
> + struct resource *r;
> +
> + /*
> + * Look for first unused memory region starting at page
> + * boundary. Skip last memory section created at boot time
> + * because it may contains unused memory pages with PG_reserved
> + * bit not set (online_pages() require PG_reserved bit set).
> + */
> +
> + r = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +
> + if (!r)
> + return NULL;
> +
> + r->name = "System RAM";
> + r->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> + r_min =
> PFN_PHYS(section_nr_to_pfn(pfn_to_section_nr(balloon_stats.boot_max_pfn) +
> 1));
> + r_size = nr_pages << PAGE_SHIFT;
> +
> + if (allocate_resource(&iomem_resource, r, r_size, r_min,
> + ULONG_MAX, PAGE_SIZE, NULL, NULL) < 0) {
> + kfree(r);
> + return NULL;
> + }
> +
> + return r;
> +}
> +
> +static struct resource *adjust_memory_resource(struct resource *r, unsigned
> long nr_pages)
> +{
> + int rc;
> +
> + if (r->end + 1 - (nr_pages << PAGE_SHIFT) == r->start) {
Will this actually occur? Say I called 'allocate_additional_memory' with 512
and got -ENOMEM (so the hypercall failed complelty). The mh->policy
MH_POLICY_STOP_AT_FIRST_ERROR. So we end up here. Assume the r_min is
0x100000000, then r->start is 0x100000000 and r->end is 0x100200000.
So:
100200001 - (200000) == 0x100000000 ?
> + rc = release_resource(r);
> + BUG_ON(rc < 0);
> + kfree(r);
> + return NULL;
> + }
> +
> + rc = adjust_resource(r, r->start, r->end + 1 - r->start -
> + (nr_pages << PAGE_SHIFT));
If we wanted 512 pages, and only got 256 and want to adjust the region, we
would want it be:
0x100000000 -> 0x100100000 right?
So with the third argument that comes out to be:
0x100200000 + 1 - 0x100000000 - (100000) = 100001
which is just one page above what we requested?
> +
> + BUG_ON(rc < 0);
Can we just do WARN_ON, and return NULL instead (and also release the resource)?
> +
> + return r;
> +}
> +
> +static int allocate_additional_memory(struct resource *r, unsigned long
> nr_pages)
> +{
> + int rc;
> + struct xen_memory_reservation reservation = {
> + .address_bits = 0,
> + .extent_order = 0,
> + .domid = DOMID_SELF
> + };
> + unsigned long flags, i, pfn, pfn_start;
> +
> + if (!nr_pages)
> + return 0;
> +
> + pfn_start = PFN_UP(r->end) - nr_pages;
> +
> + if (nr_pages > ARRAY_SIZE(frame_list))
> + nr_pages = ARRAY_SIZE(frame_list);
> +
> + for (i = 0, pfn = pfn_start; i < nr_pages; ++i, ++pfn)
> + frame_list[i] = pfn;
> +
> + set_xen_guest_handle(reservation.extent_start, frame_list);
> + reservation.nr_extents = nr_pages;
> +
> + spin_lock_irqsave(&xen_reservation_lock, flags);
> +
> + rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
> +
> + if (rc <= 0)
> + return (rc < 0) ? rc : -ENOMEM;
> +
So if we populated some of them (say we want to 512, but only did 64),
don't we want to do the loop below? Also you look to be forgetting to
do a spin_unlock_irqrestore if you quit here.
> + for (i = 0, pfn = pfn_start; i < rc; ++i, ++pfn) {
> + BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
> + phys_to_machine_mapping_valid(pfn));
> + set_phys_to_machine(pfn, frame_list[i]);
> + }
> +
> + spin_unlock_irqrestore(&xen_reservation_lock, flags);
> +
> + return rc;
> +}
> +
> +static void hotplug_allocated_memory(struct resource *r)
> {
> - unsigned long target = balloon_stats.target_pages;
> + int nid, rc;
> + resource_size_t r_size;
> + struct memory_block *mem;
> + unsigned long pfn;
> +
> + r_size = r->end + 1 - r->start;
Why bump it by one byte?
> + nid = memory_add_physaddr_to_nid(r->start);
> +
> + rc = add_registered_memory(nid, r->start, r_size);
> +
> + if (rc) {
> + pr_err("%s: add_registered_memory: Memory hotplug failed: %i\n",
> + __func__, rc);
> + balloon_stats.target_pages = balloon_stats.current_pages;
> + return;
> + }
> +
> + if (xen_pv_domain())
> + for (pfn = PFN_DOWN(r->start); pfn < PFN_UP(r->end); ++pfn)
I think you the r->start to be PFN_UP just in case the r->start is not page
aligned. Thought I am not sure it would even happen anymore, as M A Young
found the culprit that made it possible for us to setup memory regions
non-aligned and that is fixed now (in 2.6.38).
> + if (!PageHighMem(pfn_to_page(pfn))) {
> + rc = HYPERVISOR_update_va_mapping(
> + (unsigned long)__va(pfn << PAGE_SHIFT),
> + mfn_pte(pfn_to_mfn(pfn), PAGE_KERNEL),
> 0);
> + BUG_ON(rc);
> + }
>
> - target = min(target,
> - balloon_stats.current_pages +
> - balloon_stats.balloon_low +
> - balloon_stats.balloon_high);
> + rc = online_pages(PFN_DOWN(r->start), r_size >> PAGE_SHIFT);
>
> - return target;
> + if (rc) {
> + pr_err("%s: online_pages: Failed: %i\n", __func__, rc);
> + balloon_stats.target_pages = balloon_stats.current_pages;
> + return;
> + }
> +
> + for (pfn = PFN_DOWN(r->start); pfn < PFN_UP(r->end); pfn +=
> PAGES_PER_SECTION) {
Ditto. Can you do PFN_UP(r->start)?
> + mem = find_memory_block(__pfn_to_section(pfn));
> + BUG_ON(!mem);
> + BUG_ON(!present_section_nr(mem->phys_index));
> + mutex_lock(&mem->state_mutex);
> + mem->state = MEM_ONLINE;
> + mutex_unlock(&mem->state_mutex);
> + }
> +
> + balloon_stats.current_pages += r_size >> PAGE_SHIFT;
> }
>
> +static enum bp_state request_additional_memory(long credit)
> +{
> + int rc;
> + static struct resource *r;
> + static unsigned long pages_left;
> +
> + if ((credit <= 0 || balloon_stats.balloon_low ||
> + balloon_stats.balloon_high) && !r)
> + return BP_DONE;
> +
> + if (!r) {
> + r = allocate_memory_resource(credit);
> +
> + if (!r)
> + return BP_ERROR;
> +
> + pages_left = credit;
> + }
> +
> + rc = allocate_additional_memory(r, pages_left);
> +
> + if (rc < 0) {
> + if (balloon_stats.mh_policy == MH_POLICY_TRY_UNTIL_SUCCESS)
> + return BP_ERROR;
> +
> + r = adjust_memory_resource(r, pages_left);
> +
> + if (!r)
> + return BP_ERROR;
Say we failed the hypercall completly and got -ENOMEM from the
'allocate_additional_memory'.
I presume the adjust_memory_resource at this point would have deleted 'r',
which means
that (!r) and we return BP_ERROR.
But that means that we aren't following the MH_POLICY_STOP_AT_FIRST_ERROR as
the balloon_process will retry again and the again, and again??
> + } else {
> + pages_left -= rc;
> +
So say I request 512 pages (mh_policy is MH_POLICY_STOP_AT_FIRST_ERROR),
but only got 256. I adjust the pages_left to be 256 and then
> + if (pages_left)
> + return BP_HUNGRY;
we return BP_HUNGRY. That makes 'balloon_process' retry with 512 pages, and we
keep on trying and call "allocate_additional_memory", which fails once more
(returns 256), and we end up returning BP_HUNGRY, and retry... and so on.
Would it be make sense to have a check here for the
MH_POLICY_STOP_AT_FIRST_ERROR
and if so call the adjust_memory_memory_resource as well?
> + }
> +
> + hotplug_allocated_memory(r);
> +
> + r = NULL;
> +
> + return BP_DONE;
> +}
> +#else
> +static enum bp_state request_additional_memory(long credit)
> +{
> + if (balloon_stats.balloon_low && balloon_stats.balloon_high &&
> + balloon_stats.target_pages >
> balloon_stats.current_pages)
> + balloon_stats.target_pages = balloon_stats.current_pages;
> + return BP_DONE;
> +}
> +#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
> +
> static enum bp_state increase_reservation(unsigned long nr_pages)
> {
> enum bp_state state = BP_DONE;
> @@ -352,15 +547,17 @@ static enum bp_state decrease_reservation(unsigned long
> nr_pages)
> */
> static void balloon_process(struct work_struct *work)
> {
> - enum bp_state rc, state = BP_DONE;
> + enum bp_state rc, state;
> long credit;
>
> mutex_lock(&balloon_mutex);
>
> do {
> - credit = current_target() - balloon_stats.current_pages;
> + credit = balloon_stats.target_pages -
> balloon_stats.current_pages;
>
> - if (credit > 0) {
> + state = request_additional_memory(credit);
> +
> + if (credit > 0 && state == BP_DONE) {
> rc = increase_reservation(credit);
> state = (rc == BP_ERROR) ? BP_ERROR : state;
> }
> @@ -450,6 +647,11 @@ static int __init balloon_init(void)
> balloon_stats.schedule_delay = 1;
> balloon_stats.max_schedule_delay = 32;
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + balloon_stats.boot_max_pfn = max_pfn;
> + balloon_stats.mh_policy = MH_POLICY_STOP_AT_FIRST_ERROR;
> +#endif
> +
> register_balloon(&balloon_sysdev);
>
> /*
> @@ -506,6 +708,10 @@ BALLOON_SHOW(high_kb, "%lu\n",
> PAGES2KB(balloon_stats.balloon_high));
> static SYSDEV_ULONG_ATTR(schedule_delay, 0644, balloon_stats.schedule_delay);
> static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644,
> balloon_stats.max_schedule_delay);
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> +static SYSDEV_ULONG_ATTR(memory_hotplug_policy, 0644,
> balloon_stats.mh_policy);
> +#endif
> +
> static ssize_t show_target_kb(struct sys_device *dev, struct
> sysdev_attribute *attr,
> char *buf)
> {
> @@ -568,7 +774,10 @@ static struct sysdev_attribute *balloon_attrs[] = {
> &attr_target_kb,
> &attr_target,
> &attr_schedule_delay.attr,
> - &attr_max_schedule_delay.attr
> + &attr_max_schedule_delay.attr,
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + &attr_memory_hotplug_policy.attr
> +#endif
> };
>
> static struct attribute *balloon_info_attrs[] = {
> --
> 1.5.6.5
>
> --
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