changing kern.bio_transient_maxcnt fixes panic

[Stephen Mcconnell]

   changing kern.bio_transient_maxcnt fixes panic

Hi Konstantine.  I hope you are the right person to help with this.  Or
perhaps someone else on the list can help.

We (Avago) have a customer who is getting the following panic.  They are
using the mrsas (MegaRAID) driver in FreeBSD 10.  In a test, they tried to
restore a database backup of 3GB.  After the restore they queried the
database and then saw the panic.  They found this link, saying that
changing the value of kern.bio_transient_maxcnt should fix the problem.  It
did fix the problem, be we would like to know why it helped so that we’re
not just putting a band-aid on it.

*https://lists.freebsd.org/pipermail/freebsd-stable/2013-October/075577.html*
<https://lists.freebsd.org/pipermail/freebsd-stable/2013-October/075577.html>

Also, I found this link with the same type of question.

*https://docs.freebsd.org/cgi/getmsg.cgi?fetch=179246+182329+/usr/local/www/db/text/2014/freebsd-questions/20141019.freebsd-questions*
<https://docs.freebsd.org/cgi/getmsg.cgi?fetch=179246+182329+/usr/local/www/db/text/2014/freebsd-questions/20141019.freebsd-questions>

Can you explain why changing this value fixes this problem, and what we
might need to do in the driver to make a permanent fix?

Thanks for your help,

Stephen McConnell

Avago Technologies

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