Messages in this thread | | | Date | Wed, 22 Mar 2006 07:59:11 +0100 | From | Eric Dumazet <> | Subject | Re: [RFC, PATCH] avoid some atomics in open()/close() for monothreaded processes |
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Andrew Morton a écrit : > Eric Dumazet <dada1@cosmosbay.com> wrote: >> Goal : Avoid some locking/unlocking 'struct files_struct'->file_lock for mono >> threaded processes. >> >> We define files_multithreaded() function . >> >> static inline int files_multithreaded(const struct files_struct *files) >> { >> return sizeof(files->file_lock) > 0 && atomic_read(&files->count) > 1; >> } > > That's bascially sizeof(spinlock_t). That's architecture dependent and > varies wildly according to the day of week.
I used sizeof(files->file_lock) instead of sizeof(spinlock_t) because I found it more explicit , while not using ugly ifdefs.
> > It _might_ work in all situations - probably you checked that. But I still > wouldn't do it because it might break in the future. Let's be explicit and > stick the appropriate ifdefs in there. > > I'd also consider renaming it to files_shared() - processes are > multithreaded, not data structures.
Thanks for the feedback, I will redo the patch and test it on various platforms before resubmit (including performance data :) )
> > Once you're done with that we should change fget_light() and fput_light() to > use this helper. Separate patch.
Hum... this discussion is not relevant with fget_light() unless I mistaken.
Nowadays, this function doesnt take spinlock thanks to RCU
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