[Stgt-devel] add aio backing store using eventfd
Sun Jan 20 08:43:56 CET 2008
I restored the aio backing store feature because Linux finally support
a resonable AIO event notification (eventfd). I tested the feature
with 2.6.24-rc8 but it also works with 2.6.23, I guess.
This backing store doesn't use the workaround in bs_rdwr to play with
pthread and pipe, which incurs large latency.
You can specify the backing store type when adding a logical
unit. Here is an example:
$ tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 -b /var/tmp/lun1 --bstype aio
- Linux AIO works only with O_DIRECT. So this backing store mode
doesn't use page cache. You probably need fast disk to enjoy this
backing store. I guess that we still need to wait for Linux AIO to
support non O_DIRECT.
- The writeback cache is not supported yet. This always works in the
writethrough cache mode.
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