linux-kernel - Re: [BUG] Slow SATA disk - waiting in balance_dirty

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Message-ID: <20170802122901.GB2529@dhcp22.suse.cz>
Date:   Wed, 2 Aug 2017 14:29:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Philipp Hahn <hahn@...vention.de>
Cc:     linux-mm@...ck.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Slow SATA disk - waiting in balance_dirty_pages() on
 i686-pae.html

On Tue 01-08-17 12:32:40, Philipp Hahn wrote:
> Hello,
> 
> ;TL,DR: apt-get is blocked by balance_dirty_pages() with linux-{3,16
> 4.2, 4.9}, but fast after reboot.
> 
> 
> We still have several systems running 4.9.0-ucs104-686-pae. They have 16
> GiB RAM and two disk:

I would strongly discourage you from using 32b system with so much
memory. This will always bump into problems because of the inherent
kernel/userspace split. Also I would bet that the problem you are seeing
is the lack of lowmem memory which is considered for the dirty writers
throttling unless you have vm.highmem_is_dirtyable is set to 1 which is
not the case in your setup.
-- 
Michal Hocko
SUSE Labs