linux-kernel - Re: kernel BUG at mm/swap

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Message-ID: <CABXGCsNRpq=AF1aRgyquszy2MZzVfKZwrKXiSW-PnGiAR652cg@mail.gmail.com>
Date:   Thu, 25 Jul 2019 11:17:21 +0500
From:   Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     huang ying <huang.ying.caritas@...il.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org
Subject: Re: kernel BUG at mm/swap_state.c:170!

On Tue, 23 Jul 2019 at 10:08, Huang, Ying <ying.huang@...el.com> wrote:
>
> Thanks!  I have found another (easier way) to reproduce the panic.
> Could you try the below patch on top of v5.2-rc2?  It can fix the panic
> for me.
>

Thanks! Amazing work! The patch fixes the issue completely. The system
worked at a high load of 16 hours without failures.

But still seems to me that page cache is being too actively crowded
out with a lack of memory. Since, in addition to the top speed SSD on
which the swap is located, there is also the slow HDD in the system
that just starts to rustle continuously when swap being used. It would
seem better to push some of the RAM onto a fast SSD into the swap
partition than to leave the slow HDD without a cache.

https://imgur.com/a/e8TIkBa

But I am afraid it will be difficult to implement such an algorithm
that analyzes the waiting time for the file I/O and waiting for paging
(memory) and decides to leave parts in memory where the waiting time
is more higher it would be more efficient for systems with several
drives with access speeds can vary greatly. By waiting time I mean
waiting time reading/writing to storage multiplied on the count of
hits. Thus, we will not just keep in memory the most popular parts of
the memory/disk, but also those parts of which read/write where was
most costly.

--
Best Regards,
Mike Gavrilov.