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Date: Wed, 21 Apr 2010 18:02:48 -0700
From: Dmitry Torokhov <dtor@...are.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "pv-drivers@...are.com" <pv-drivers@...are.com>,
Jeremy Fitzhardinge <jeremy@...p.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Avi Kivity <avi@...hat.com>
Subject: Re: [Pv-drivers] [PATCH v2] VMware Balloon driver
On Wed, Apr 21, 2010 at 05:00:49PM -0700, Dmitry Torokhov wrote:
> On Wed, Apr 21, 2010 at 04:54:49PM -0700, Andrew Morton wrote:
> > On Thu, 15 Apr 2010 14:00:31 -0700
> > Dmitry Torokhov <dtor@...are.com> wrote:
> >
> > > This is standalone version of VMware Balloon driver. Ballooning is a
> > > technique that allows hypervisor dynamically limit the amount of memory
> > > available to the guest (with guest cooperation). In the overcommit
> > > scenario, when hypervisor set detects that it needs to shuffle some memory,
> > > it instructs the driver to allocate certain number of pages, and the
> > > underlying memory gets returned to the hypervisor. Later hypervisor may
> > > return memory to the guest by reattaching memory to the pageframes and
> > > instructing the driver to "deflate" balloon.
> > >
> > > Signed-off-by: Dmitry Torokhov <dtor@...are.com>
> > > ---
> > >
> > > Unlike previous version, that tried to integrate VMware ballooning transport
> > > into virtio subsystem, and use stock virtio_ballon driver, this one implements
> > > both controlling thread/algorithm and hypervisor transport.
> > >
> > > We are submitting standalone driver because KVM maintainer (Avi Kivity)
> > > expressed opinion (rightly) that our transport does not fit well into
> > > virtqueue paradigm and thus it does not make much sense to integrate
> > > with virtio.
> > >
> > > There were also some concerns whether current ballooning technique is
> > > the right thing. If there appears a better framework to achieve this we
> > > are prepared to evaluate and switch to using it, but in the meantime
> > > we'd like to get this driver upstream.
> > >
> > > Changes since v1:
> > > - added comments throughout the code;
> > > - exported stats moved from /proc to debugfs;
> > > - better changelog.
> > >
> > >
> > > ...
> > >
> > > +#define VMW_BALLOON_NOSLEEP_ALLOC_MAX 16384U
> > > +
> > > +#define VMW_BALLOON_RATE_ALLOC_MIN 512U
> > > +#define VMW_BALLOON_RATE_ALLOC_MAX 2048U
> > > +#define VMW_BALLOON_RATE_ALLOC_INC 16U
> > > +
> > > +#define VMW_BALLOON_RATE_FREE_MIN 512U
> > > +#define VMW_BALLOON_RATE_FREE_MAX 16384U
> > > +#define VMW_BALLOON_RATE_FREE_INC 16U
> >
> > hum. What do these do and what units are they in? Needs a comment?
>
> These control inflating/deflating rate of the ballon, mesured in
> pages/sec. I will add a comment.
>
> >
> > >
> > > ...
> > >
> > > +#define VMWARE_BALLOON_CMD(cmd, data, result) \
> > > +({ \
> > > + unsigned long __stat, __dummy1, __dummy2; \
> > > + __asm__ __volatile__ ("inl (%%dx)" : \
> > > + "=a"(__stat), \
> > > + "=c"(__dummy1), \
> > > + "=d"(__dummy2), \
> > > + "=b"(result) : \
> > > + "0"(VMW_BALLOON_HV_MAGIC), \
> > > + "1"(VMW_BALLOON_CMD_##cmd), \
> > > + "2"(VMW_BALLOON_HV_PORT), \
> > > + "3"(data) : \
> > > + "memory"); \
> > > + result &= -1UL; \
> > > + __stat & -1UL; \
> > > +})
> >
> > This is OK for both x86_32 and x86_64?
>
> Yes it is.
>
> >
> > Was it actually intended that this driver be enabled for 32-bit?
> >
>
> Yes.
>
> > > +#define STATS_INC(stat) (stat)++
> > > +
> > > +struct vmballoon_stats {
> > > + unsigned int timer;
> > > +
> > > + /* allocation statustics */
> > > + unsigned int alloc;
> > > + unsigned int alloc_fail;
> > > + unsigned int sleep_alloc;
> > > + unsigned int sleep_alloc_fail;
> > > + unsigned int refused_alloc;
> > > + unsigned int refused_free;
> > > + unsigned int free;
> > > +
> > > + /* monitor operations */
> > > + unsigned int lock;
> > > + unsigned int lock_fail;
> > > + unsigned int unlock;
> > > + unsigned int unlock_fail;
> > > + unsigned int target;
> > > + unsigned int target_fail;
> > > + unsigned int start;
> > > + unsigned int start_fail;
> > > + unsigned int guest_type;
> > > + unsigned int guest_type_fail;
> > > +};
> > > +
> > > +struct vmballoon {
> > > +
> > > + /* list of reserved physical pages */
> > > + struct list_head pages;
> > > +
> > > + /* transient list of non-balloonable pages */
> > > + struct list_head refused_pages;
> > > +
> > > + /* balloon size in pages */
> > > + unsigned int size;
> > > + unsigned int target;
> > > +
> > > + /* reset flag */
> > > + bool reset_required;
> > > +
> > > + /* adjustment rates (pages per second) */
> > > + unsigned int rate_alloc;
> > > + unsigned int rate_free;
> > > +
> > > + /* slowdown page allocations for next few cycles */
> > > + unsigned int slow_allocation_cycles;
> > > +
> > > + /* statistics */
> > > + struct vmballoon_stats stats;
> > > +
> > > + /* debugfs file exporting statistics */
> > > + struct dentry *dbg_entry;
> > > +
> > > + struct sysinfo sysinfo;
> > > +
> > > + struct delayed_work dwork;
> > > +};
> >
> > afaict all the stats stuff is useless if CONFIG_DEBUG_FS=n. Perhaps in
> > that case the vmballoon.stats field should be omitted and STATS_INC
> > be made a no-op?
> >
>
> OK, will do.
>
> Thanks Andrew.
>
OK, so here is the incremental patch addressing your comments. Or do you
want the entire thing resent?
Thanks.
--
Dmitry
vmware-balloon: miscellaneous fixes
- document rate allocation constants
- do not compile statistics code when debugfs is disabled
- fix compilation error when debugfs is disabled
Signed-off-by: Dmitry Torokhov <dtor@...are.com>
---
drivers/misc/vmware_balloon.c | 38 +++++++++++++++++++++++++++++++-------
1 files changed, 31 insertions(+), 7 deletions(-)
diff --git a/drivers/misc/vmware_balloon.c b/drivers/misc/vmware_balloon.c
index 90bba04..e7161c4 100644
--- a/drivers/misc/vmware_balloon.c
+++ b/drivers/misc/vmware_balloon.c
@@ -50,12 +50,28 @@ MODULE_ALIAS("dmi:*:svnVMware*:*");
MODULE_ALIAS("vmware_vmmemctl");
MODULE_LICENSE("GPL");
+/*
+ * Various constants controlling rate of inflaint/deflating balloon,
+ * measured in pages.
+ */
+
+/*
+ * Rate of allocating memory when there is no memory pressure
+ * (driver performs non-sleeping allocations).
+ */
#define VMW_BALLOON_NOSLEEP_ALLOC_MAX 16384U
+/*
+ * Rates of memory allocaton when guest experiences memory pressure
+ * (driver performs sleeping allocations).
+ */
#define VMW_BALLOON_RATE_ALLOC_MIN 512U
#define VMW_BALLOON_RATE_ALLOC_MAX 2048U
#define VMW_BALLOON_RATE_ALLOC_INC 16U
+/*
+ * Rates for releasing pages while deflating balloon.
+ */
#define VMW_BALLOON_RATE_FREE_MIN 512U
#define VMW_BALLOON_RATE_FREE_MAX 16384U
#define VMW_BALLOON_RATE_FREE_INC 16U
@@ -85,6 +101,10 @@ MODULE_LICENSE("GPL");
/* Maximum number of page allocations without yielding processor */
#define VMW_BALLOON_YIELD_THRESHOLD 1024
+
+/*
+ * Hypervisor communication port definitions.
+ */
#define VMW_BALLOON_HV_PORT 0x5670
#define VMW_BALLOON_HV_MAGIC 0x456c6d6f
#define VMW_BALLOON_PROTOCOL_VERSION 2
@@ -125,8 +145,7 @@ MODULE_LICENSE("GPL");
__stat & -1UL; \
})
-#define STATS_INC(stat) (stat)++
-
+#ifdef CONFIG_DEBUG_FS
struct vmballoon_stats {
unsigned int timer;
@@ -152,6 +171,11 @@ struct vmballoon_stats {
unsigned int guest_type_fail;
};
+#define STATS_INC(stat) (stat)++
+#else
+#define STATS_INC(stat)
+#endif
+
struct vmballoon {
/* list of reserved physical pages */
@@ -174,11 +198,13 @@ struct vmballoon {
/* slowdown page allocations for next few cycles */
unsigned int slow_allocation_cycles;
+#ifdef CONFIG_DEBUG_FS
/* statistics */
struct vmballoon_stats stats;
/* debugfs file exporting statistics */
struct dentry *dbg_entry;
+#endif
struct sysinfo sysinfo;
@@ -637,7 +663,7 @@ static void vmballoon_work(struct work_struct *work)
}
/*
- * PROCFS Interface
+ * DEBUGFS Interface
*/
#ifdef CONFIG_DEBUG_FS
@@ -727,11 +753,11 @@ static inline int vmballoon_debugfs_init(struct vmballoon *b)
return 0;
}
-static inline void vmballoon_debugfs_exit(void)
+static inline void vmballoon_debugfs_exit(struct vmballoon *b)
{
}
-#endif /* CONFIG_PROC_FS */
+#endif /* CONFIG_DEBUG_FS */
static int __init vmballoon_init(void)
{
@@ -750,8 +776,6 @@ static int __init vmballoon_init(void)
return -ENOMEM;
}
- /* initialize global state */
- memset(&balloon, 0, sizeof(balloon));
INIT_LIST_HEAD(&balloon.pages);
INIT_LIST_HEAD(&balloon.refused_pages);
--
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