From: Colin Hamilton <colin.hamilton@suse.com>
To: kernelnewbies@kernelnewbies.org
Subject: __vm_enough_memory calculation when deactivating a swap device
Date: Sun, 30 Jun 2019 13:57:27 -0600 (MDT) [thread overview]
Message-ID: <nycvar.YFH.7.76.1906301343130.9160@yvahk-hern.fhfr> (raw)
Hey everyone,
When the sys_swapoff() routine is attempting to deactivate a swap area
it checks to make sure there is enough free space to swap-in the
required new page frames from the deactivating swap device. In
__vm_enough_memory it adds to the free variable counting all currently
active swap pages, including from the device that is to be deactivated,
with:
free += get_nr_swap_pages();
My question/confusion is, why doesn't the kernel have code in
place to exclude free swap pages from the device that is to be
deactivated when __vm_enough_memory is used for this purpose?
Is it because it would require reworking too much of what approximately
works now? In other words, is this a cost/benefit decision to not have
that added logic? Or perhaps I'm just misunderstanding how something is
supposed to work?
Thanks,
--
Colin Hamilton <colin.hamilton@suse.com>
SUSE
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