* [PATCH] Drivers: hv: hv_balloon: eliminate jumps in piecewiese linear floor function
@ 2015-03-26 10:26 Vitaly Kuznetsov
2015-03-26 16:17 ` Laszlo Ersek
0 siblings, 1 reply; 2+ messages in thread
From: Vitaly Kuznetsov @ 2015-03-26 10:26 UTC (permalink / raw)
To: K. Y. Srinivasan
Cc: Haiyang Zhang, devel, linux-kernel, Dexuan Cui, Laszlo Ersek
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] Drivers: hv: hv_balloon: eliminate jumps in piecewiese linear floor function
2015-03-26 10:26 [PATCH] Drivers: hv: hv_balloon: eliminate jumps in piecewiese linear floor function Vitaly Kuznetsov
@ 2015-03-26 16:17 ` Laszlo Ersek
0 siblings, 0 replies; 2+ messages in thread
From: Laszlo Ersek @ 2015-03-26 16:17 UTC (permalink / raw)
To: Vitaly Kuznetsov, K. Y. Srinivasan
Cc: Haiyang Zhang, devel, linux-kernel, Dexuan Cui
On 03/26/15 11:26, Vitaly Kuznetsov wrote:
> 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;
> }
>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Thanks!
Laszlo
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