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Commit 1c7db96f authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
Browse files

Drivers: hv: balloon: Prevent the host from ballooning the guest too low 



Based on the amount of memory being managed set a floor on how low the
guest can be ballooned.

Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e500d158

drivers/hv/hv_balloon.c

+34 −1
Original line number Diff line number Diff line
@@ -523,6 +523,34 @@ static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg) 
	}

}



unsigned long compute_balloon_floor(void)

{

	unsigned long min_pages;

#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))

	/* Simple continuous piecewiese linear function:

	 *  max MiB -> min MiB  gradient

	 *       0         0

	 *      16        16

	 *      32        24

	 *     128        72    (1/2)

	 *     512       168    (1/4)

	 *    2048       360    (1/8)

	 *    8192       552    (1/32)

	 *   32768      1320

	 *  131072      4392

	 */

	if (totalram_pages < MB2PAGES(128))

		min_pages = MB2PAGES(8) + (totalram_pages >> 1);

	else if (totalram_pages < MB2PAGES(512))

		min_pages = MB2PAGES(40) + (totalram_pages >> 2);

	else if (totalram_pages < MB2PAGES(2048))

		min_pages = MB2PAGES(104) + (totalram_pages >> 3);

	else

		min_pages = MB2PAGES(296) + (totalram_pages >> 5);

#undef MB2PAGES

	return min_pages;

}



/*

 * Post our status as it relates memory pressure to the

 * host. Host expects the guests to post this status
@@ -552,9 +580,14 @@ static void post_status(struct hv_dynmem_device *dm) 
	 * The host expects the guest to report free memory.

	 * Further, the host expects the pressure information to

	 * include the ballooned out pages.

	 * For a given amount of memory that we are managing, we

	 * need to compute a floor below which we should not balloon.

	 * Compute this and add it to the pressure report.

	 */

	status.num_avail = val.freeram;

	status.num_committed = vm_memory_committed() + dm->num_pages_ballooned;

	status.num_committed = vm_memory_committed() +

				dm->num_pages_ballooned +

				compute_balloon_floor();



	vmbus_sendpacket(dm->dev->channel, &status,

				sizeof(struct dm_status),