Messages in this thread |  | | | Date | Fri, 26 Aug 2005 00:51:30 +1000 | | From | Nick Piggin <> | | Subject | Re: [PATCH] removes filp_count_lock and changes nr_files type to atomic_t |
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Eric Dumazet wrote: > Nick Piggin a écrit : >
>> Would you just be able to add the atomic sysctl handler that >> Christoph suggested? >> > > Quite a lot of work indeed, and it would force to convert 3 int > (nr_files, nr_free_files, max_files) to 3 atomic_t. I feel bad > introducing a lot of sysctl rework for a tiny change (removing > filp_count_lock) >
True, I didn't notice that.
>> This introduces lost update problems. 2 CPUs may store to nr_files >> in the opposite order that they incremented atomic_nr_files. >> > > That's true, and the difference can be relatively important in case of > preemption. > > Each time the true and correct value (atomic_nr_files) is updated, a > copy is done on nr_files : as nr_files is only used to be a guard value > against too many file allocations, a somewhat 'lazy' value has no impact > at all. >
OK, well I would prefer you do the proper atomic operations throughout where it "really matters" in file_table.c, and do your lazy synchronize with just the sysctl exported value.
Unless the fs people had a problem with that.
And you may as well get rid of the atomic_inc_return which can be more expensive on some platforms and doesn't buy you much. atomic_inc; atomic_read; Should be enough if you don't care about lost updates here, yeah?
Nick
-- SUSE Labs, Novell Inc.
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