Messages in this thread | | | Subject | Re: [patch 1/4] spinlock: lockbreak cleanup | From | Lee Schermerhorn <> | Date | Thu, 01 Nov 2007 11:39:59 -0400 |
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On Thu, 2007-11-01 at 15:29 +0100, Nick Piggin wrote: > On Thu, Nov 01, 2007 at 03:06:05PM +0100, Peter Zijlstra wrote: > > On Thu, 2007-11-01 at 15:02 +0100, Nick Piggin wrote: > > > > > Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to > > > decouple it from the spinlock implementation, and make it typesafe (rwlocks > > > do not have any need_lockbreak sites -- why do they even get bloated up > > > with that break_lock then?). > > > > IIRC Lee has a few patches floating about that do introduce lockbreak > > stuff for rwlocks. > > Well that would be a good reason to introduce a break_lock for them, > but previously not so much... we have rwlocks in some slightly space > critical structures (vmas, inodes, etc). > > I guess it was done to make the "template" hacks eaiser. I don't really > find that in good taste, especially for important core infrastructure. > Anyway.
Actually, what I had/have is a cond_resched_rwlock() that I needed to convert the i_mmap_lock() to rw for testing reclaim scalability. [I've seen a large system running an Oracle OLTP load hang spitting "cpu soft lockup" messages with all cpus spinning on a i_mmap_lock spin lock.] One of the i_mmap_lock paths uses cond_resched_lock() for spin locks. To do a straight forward conversion [and maybe that isn't the right approach], I created the cond_resched_rwlock() function by generalizing the cond_sched_lock() code and creating both spin and rw lock wrappers. I took advantage of the fact that, currently, need_lockbreak() is a macro and that both spin and rw locks have/had the break_lock member. Typesafe functions would probably be preferrable, if we want to keep break_lock for rw spin locks.
Here's the most recent posting:
http://marc.info/?l=linux-mm&m=118980356306014&w=4
See the changes to sched.[ch]. Should apply to 23-mm1 with offsets and minor fixup in fs/inode.c.
Lee
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