From: Michal Hocko <mhocko@suse.cz>
To: Shawn Joo <sjoo@nvidia.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"andi@firstfloor.org" <andi@firstfloor.org>
Subject: Re: page allocation failure
Date: Tue, 31 Jul 2012 15:52:58 +0200 [thread overview]
Message-ID: <20120731135258.GB7867@tiehlicka.suse.cz> (raw)
In-Reply-To: <5F2C6DA655B36C43B21C7FB179CEC9F4E3F157B9DA@HKMAIL02.nvidia.com>
On Tue 31-07-12 13:32:36, Shawn Joo wrote:
> Thank you for attention and comment, here is following question.
>
>
>
> 1. In general if order 3(32KB) is required to be allocated, if
> "size-32768" cache does not have available slab, then "size-32768"
> will request memory from buddy Here watermark is involved as important
> factor.
>
> (I would like to know how to increase the number of object on the
> cache, because when cache is created by "kmem_cache_create", there is
> only object size, but no number of the object)
I am not familiar with the slab allocator much but I do not think this
is possible. At least slab drops unused objects if the system is under
memory pressure so I do not see how this would help. I guess the problem
is the high order allocation itself (maybe you should consider disable
jumbo frames?)
>
> d my understanding is correct?, please correct.
>
> 2. In my init.rc, min_free_order_shift is set to 4.
I am not familiar with such a tunable. Google says it might be something
android specific
(https://dev.openwrt.org/browser/trunk/target/linux/goldfish/patches-2.6.30/0055-mm-Add-min_free_order_shift-tunable.patch?rev=16459)
> If I decrease this value, it should be helpful.
No, quite opposite. From the quick glance at the patch it makes the
rules for high order balancing in __zone_watermark_ok more relaxed.
min_free_order_shift == 1 is what we do in the upstream kernel.
Anyway this will not help much if these allocations are continuous. It
would just get the system under a bigger memory pressure because it
allows to allocate more memory.
>
> any recommend size of "min_free_order_shift"? If I can have doc about
> it, it will be helpful.
You have to ask the patch author for that.
--
Michal Hocko
SUSE Labs
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prev parent reply other threads:[~2012-07-31 13:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-30 13:25 Shawn Joo
2012-07-30 14:13 ` Michal Hocko
2012-07-31 5:32 ` Shawn Joo
2012-07-31 13:52 ` Michal Hocko [this message]
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