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From: Justin TerAvest <teravest@google.com>
Date: Mon, 28 Feb 2011 16:19:43 -0800
Message-ID: <AANLkTinXa4Zjg0zGbPQRZQi2QW_-0y+PBzQwcdjPLVKZ@mail.gmail.com>
Subject: RFC: default group_isolation to 1, remove option
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Chad Talbott <ctalbott@google.com>, Nauman Rafique <nauman@google.com>,
        Divyesh Shah <dpshah@google.com>, lkml <linux-kernel@vger.kernel.org>,
        Gui Jianfeng <guijianfeng@cn.fujitsu.com>,
        Jens Axboe <axboe@kernel.dk>
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Hi Vivek,

I'd like to propose removing the group_isolation setting and changing
the default to 1. Do we know if anyone is using group_isolation=0 to get
easy group separation between sequential readers and random readers?

Allowing group_isolation complicates implementing per-cgroup request
descriptor pools when a queue is moved to the root group. Specifically,
if we have pools per-cgroup, we would be forced to use request
descriptors from the pool for the "original" cgroup, while the requests
are actually being serviced by the root cgroup.

That might be acceptable, but I figured this would be a good opportunity
to revisit keeping queues within their original groups.

I know this discussion has come up before. I'm curious if we have a good
reason to keep it around right now. I'd be happy to do some investigation
to help make my case.

Thanks,
Justin
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