[dm-devel] A patchset to limit the number of outstanding bios

[Mikulas Patocka]

Hi

I'm announcing the release of a patchset that limits the number of 
outstanding bios in the device mapper.

The patchset is at 
http://people.redhat.com/~mpatocka/patches/kernel/dm-limit-outstanding-bios/

The default limit is 1024, the minimum limit is 4 (but I verified that the 
testsuite works even with limit 1). The limit can be set in 
/sys/block/dm-*/queue/nr_requests

The limit for newly created dm devices can be set in 
/sys/module/dm_mod/parameters/default_nr_requests (for example, you can 
set it before running the testsuite or some benchmark).

The patchset could possibly fix bug 1010466.

Note that the patch "punt-to-workqueue.patch" is required, otherwise we 
get lockups in the testsuite at low nr_requests values. The patch 
"fix-counting.patch" isn't required, but it is included to avoid patch 
conflicts.

Mikulas