On Wed, Aug 5, 2015 at 4:53 AM, Kirill A. Shutemov <kir...@shutemov.name> wrote: >> 'only' if it's multi-threaded, i.e. when some workload cares so much about >> performance that it uses multiple threads? >> >> Can you see the contradiction there? > > I can. man 2 unshare: > > CLONE_NEWUSER requires that the calling process is not threaded; > > The workload cares so much about performance that it ignores API > requirements. Some slow down looks like a fair price to me. To be fair, the entire reason for this patch is that the slow path (mm_users > 1) can happen even when the process is single-threaded. I was concerned about how expensive current_is_single_threaded looked as well, but didn't see any lightweight alternatives short of adding a field to mm_struct. Do folks think it's worth going down that route instead?
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