Messages in this thread | | | From | Naoya Horiguchi <> | Subject | Re: [PATCH 3/3] HWPOISON: improve handling/reporting of memory error on dirty pagecache | Date | Sun, 12 Aug 2012 11:19:21 -0400 |
| |
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
| |