Hi, On Sun, Aug 12, 2012 at 05:28:44AM +0200, Andi Kleen wrote: > > > That function uses a global lock. fdatawait is quite common. This will > > > likely cause performance problems in IO workloads. > > > > OK, I should avoid it. > > Maybe just RCU the hash table. OK. > > > You need to get that lock out of the hot path somehow. > > > > > > Probably better to try to put the data into a existing data structure, > > > or if you cannot do that you would need some way to localize the lock. > > > > Yes, I have thought about adding some data like new pagecache tag or > > new members in struct address_space, but it makes the size of heavily > > used data structure larger so I'm not sure it's acceptable. > > And localizing the lock is worth trying, I think. > > It's cheaper than a hash table lookup in the hot path. > > > > Or at least make it conditional of hwpoison errors being around. > > > > I'll try to do your suggestions, but I'm not sure your point of the > > last one. Can you explain more about 'make it conditional' option? > > The code should check some flag first that is only set when hwpoison > happened on the address space (or global, but that would mean that > performance can go down globally when any error is around) I defined hwpoison_file_range() and hwpoison_partial_write() as wrapper functions of __hwpoison_* variants, and they hold hwp_dirty_lock only if AS_HWPOISON flag in mapping is set. So I hope we already did it. But yes, I understand that in general a global lock is not good, so I'll try to do other options. Thank you, Naoya -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>