From: Laura Abbott <lauraa@codeaurora.org>
To: Heesub Shin <heesub.shin@samsung.com>,
Pintu Kumar <pintu.k@samsung.com>,
akpm@linux-foundation.org, gregkh@linuxfoundation.org,
john.stultz@linaro.org, rebecca@android.com, ccross@android.com,
devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org
Cc: iqbal.ams@samsung.com, pintu_agarwal@yahoo.com, vishnu.ps@samsung.com
Subject: Re: [PATCH 1/1] [ion]: system-heap use PAGE_ALLOC_COSTLY_ORDER for high order
Date: Mon, 06 Oct 2014 07:07:37 -0700 [thread overview]
Message-ID: <5432A229.70309@codeaurora.org> (raw)
In-Reply-To: <54326EAF.8060004@samsung.com>
On 10/6/2014 3:27 AM, Heesub Shin wrote:
> Hello Kumar,
>
> On 10/06/2014 05:31 PM, Pintu Kumar wrote:
>> The Android ion_system_heap uses allocation fallback mechanism
>> based on 8,4,0 order pages available in the system.
>> It changes gfp flags based on higher order allocation request.
>> This higher order value is hard-coded as 4, instead of using
>> the system defined higher order value.
>> Thus replacing this hard-coded value with PAGE_ALLOC_COSTLY_ORDER
>> which is defined as 3.
>> This will help mapping the higher order request in system heap with
>> the actual allocation request.
>
> Quite reasonable.
>
> Reviewed-by: Heesub Shin <heesub.shin@samsung.com>
>
> BTW, Anyone knows how the allocation order (8,4 and 0) was decided? I
> think only Google guys might know the answer.
>
> regards,
> heesub
>
My understanding was this was completely unrelated to the costly order
and was related to the page sizes corresponding to IOMMU page sizes
(1MB, 64K, 4K). This won't make a difference for the uncached page
pool case but for the not page pool case, I'm not sure if there would
be a benefit for trying to get 32K pages with some effort vs. just
going back to 4K pages.
Do you have any data/metrics that show a benefit from this patch?
Thanks,
Laura
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
prev parent reply other threads:[~2014-10-06 14:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-06 8:31 Pintu Kumar
2014-10-06 10:27 ` Heesub Shin
2014-10-06 14:07 ` Laura Abbott [this message]
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