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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
	devel@linuxdriverproject.org, linux-kernel@vger.kernel.org,
	Dexuan Cui <decui@microsoft.com>,
	Laszlo Ersek <lersek@redhat.com>
Subject: [PATCH] Drivers: hv: hv_balloon: eliminate jumps in piecewiese linear floor function
Date: Thu, 26 Mar 2015 11:26:53 +0100	[thread overview]
Message-ID: <1427365613-29528-1-git-send-email-vkuznets@redhat.com> (raw)

Commit 79208c57da53 ("Drivers: hv: hv_balloon: Make adjustments in computing
the floor") was inacurate as it introduced a jump in our piecewiese linear
'floor' function:

At 2048MB we have:
Left limit:
104 + 2048/8 = 360
Right limit:
256 + 2048/16 = 384 (so the right value is 232)

We now have to make an adjustment at 8192 boundary:
232 + 8192/16 = 744
512 + 8192/32 = 768 (so the right value is 488)

Suggested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hv_balloon.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 014256a..16d52da 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -966,8 +966,8 @@ static unsigned long compute_balloon_floor(void)
 	 *     128        72    (1/2)
 	 *     512       168    (1/4)
 	 *    2048       360    (1/8)
-	 *    8192       768    (1/16)
-	 *   32768      1536	(1/32)
+	 *    8192       744    (1/16)
+	 *   32768      1512	(1/32)
 	 */
 	if (totalram_pages < MB2PAGES(128))
 		min_pages = MB2PAGES(8) + (totalram_pages >> 1);
@@ -976,9 +976,9 @@ static unsigned long compute_balloon_floor(void)
 	else if (totalram_pages < MB2PAGES(2048))
 		min_pages = MB2PAGES(104) + (totalram_pages >> 3);
 	else if (totalram_pages < MB2PAGES(8192))
-		min_pages = MB2PAGES(256) + (totalram_pages >> 4);
+		min_pages = MB2PAGES(232) + (totalram_pages >> 4);
 	else
-		min_pages = MB2PAGES(512) + (totalram_pages >> 5);
+		min_pages = MB2PAGES(488) + (totalram_pages >> 5);
 #undef MB2PAGES
 	return min_pages;
 }
-- 
1.9.3


             reply	other threads:[~2015-03-26 10:27 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-26 10:26 Vitaly Kuznetsov [this message]
2015-03-26 16:17 ` [PATCH] Drivers: hv: hv_balloon: eliminate jumps in piecewiese linear floor function Laszlo Ersek

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