linux-kernel - Re: [RFC][PATCH 4/5] memory_pressure

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Date:	Wed, 16 Jan 2008 00:39:55 +0100
From:	"Daniel Spång" <daniel.spang@...il.com>
To:	"Rik van Riel" <riel@...hat.com>
Cc:	"KOSAKI Motohiro" <kosaki.motohiro@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"Marcelo Tosatti" <marcelo@...ck.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH 4/5] memory_pressure_notify() caller

On 1/15/08, Rik van Riel <riel@...hat.com> wrote:
>
> On Tue, 15 Jan 2008 23:55:17 +0100
> "Daniel Spång" <daniel.spang@...il.com> wrote:
>
> > The notification fires after only ~100 MB allocated, i.e., when page
> > reclaim is beginning to nag from page cache. Isn't this a bit early?
> > Repeating the test with swap enabled results in a notification after
> > ~600 MB allocated, which is more reasonable and just before the system
> > starts to swap.
>
> Your issue may have more to do with the fact that the
> highmem zone is 128MB in size and some balancing issues
> between __alloc_pages and try_to_free_pages.

I don't think so. I ran the test again without highmem and noticed the
same behaviour:

$ cat /proc/meminfo
MemTotal:       895876 kB
MemFree:        111292 kB
Buffers:           924 kB
Cached:         768664 kB
SwapCached:          0 kB
Active:           9196 kB
Inactive:       767480 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       895876 kB
LowFree:        111292 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:              32 kB
Writeback:           0 kB
AnonPages:        7108 kB
Mapped:           1224 kB
Slab:             4288 kB
SReclaimable:     1316 kB
SUnreclaim:       2972 kB
PageTables:        448 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:    447936 kB
Committed_AS:    19676 kB
VmallocTotal:   122872 kB
VmallocUsed:       904 kB
VmallocChunk:   121864 kB

Start to allocate memory, 10 MB every second, exit on notification
which happened after 110 MB.

$ cat /proc/meminfo #after
MemTotal:       895876 kB
MemFree:        116748 kB
Buffers:           904 kB
Cached:         762944 kB
SwapCached:          0 kB
Active:          12864 kB
Inactive:       758064 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       895876 kB
LowFree:        116748 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:               4 kB
Writeback:           0 kB
AnonPages:        7108 kB
Mapped:           1224 kB
Slab:             4284 kB
SReclaimable:     1316 kB
SUnreclaim:       2968 kB
PageTables:        448 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
CommitLimit:    447936 kB
Committed_AS:    19676 kB
VmallocTotal:   122872 kB
VmallocUsed:       904 kB
VmallocChunk:   121864 kB
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