Hi,
I have read back in the kernel-archives, and found this messages, about the
same theme, but there is one difference!
On the old messages:
>Nate Diller wrote:
> just found the culprit. guess i should have read the code the first
> time. get_dirty_limits() in drivers/block/page_writeback.c has a
> hard-coded upper limit to dirty_ratio. it's capped to half of the
> unmapped pages, so maybe 30-40% of your system's memory. so if you are
> brave, just remove the "/ 2" parts from the 'if (dirty_ratio >
> unmapped_ratio / 2) dirty_ratio = unmapped_ratio / 2;' check, and you
> can have all the OOM goodness you want.
...
>I changed that bit of code to:
>
> if (dirty_ratio > unmapped_ratio - 10)
> dirty_ratio = unmapped_ratio - 10;
>
>and added a couple of sanity checks so that it couldn't get below 5 or
above 95.
>
>Then set /proc/sys/vm/dirty_ratio to 95 and dirty_background_ratio to 1.
In this case, this modification is only for the *dirty* memory buffer.
I want to use more buffer *cache*! :-)
The unwritten dirty memory ratio is good enough for me.
Anybody has an idea?
Cheers,
Janos
----- Original Message -----
From: "Roger Heflin" <[email protected]>
To: "'JaniD++'" <[email protected]>; <[email protected]>
Sent: Monday, December 19, 2005 7:15 PM
Subject: RE: buffer cache question
>
>
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]] On Behalf Of JaniD++
> > Sent: Sunday, December 18, 2005 3:09 PM
> > To: [email protected]
> > Subject: buffer cache question
> >
> > Hello, list,
> >
> > I use 4 disk nodes with NBD.
> > All of my nodes have 2GB ram.
> >
> > But the buffer cache newer rise over 830MB.
> >
> > Is there some limit?
>
> For writes only 40% of the ram can be "dirty".
>
> > Where can i change this limit? (if it is)
>
> I believe there is a way to change it, I am pretty sure that it has
> been discussed on the kernel list a couple of months ago, I
> don't remember exactly what the change is, and I think the change
> was more complicated that was obvious.
>
> The previous subject on a similar thing was:
> "kernel 2.6.13 buffer strangeness"
>
> Roger
>
> >
> > Thanks,
> > Janos
> >
> > [root@st-0001 root]# free
> > total used free shared
> > buffers cached
> > Mem: 2073152 933188 1139964 0
> > 836776 43416
> > -/+ buffers/cache: 52996 2020156
> > Swap: 0 0 0
> > [root@st-0001 root]# cat /proc/meminfo
> > MemTotal: 2073152 kB
> > MemFree: 1139012 kB
> > Buffers: 835928 kB
> > Cached: 43448 kB
> > SwapCached: 0 kB
> > Active: 12872 kB
> > Inactive: 871424 kB
> > HighTotal: 1179584 kB
> > HighFree: 1129764 kB
> > LowTotal: 893568 kB
> > LowFree: 9248 kB
> > SwapTotal: 0 kB
> > SwapFree: 0 kB
> > Dirty: 0 kB
> > Writeback: 0 kB
> > Mapped: 9104 kB
> > Slab: 30248 kB
> > CommitLimit: 1036576 kB
> > Committed_AS: 15428 kB
> > PageTables: 408 kB
> > VmallocTotal: 114680 kB
> > VmallocUsed: 196 kB
> > VmallocChunk: 114476 kB
> > [root@st-0001 root]#
> >
> > -
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