Re: [PATCH] mm: filemap: Avoid unnecessary barries and waitqueue lookups in unlock_page fastpath v5

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, May 21, 2014 at 02:26:22PM -0700, Andrew Morton wrote:
> > +static inline void
> > +__prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait,
> > +			struct page *page, int state, bool exclusive)
> 
> Putting MM stuff into core waitqueue code is rather bad.  I really
> don't know how I'm going to explain this to my family.

Right, so we could avoid all that and make the functions in mm/filemap.c
rather large and opencode a bunch of wait.c stuff.

Which is pretty much what I initially pseudo proposed.

> > +		__ClearPageWaiters(page);
> 
> We're freeing the page - if someone is still waiting on it then we have
> a huge bug?  It's the mysterious collision thing again I hope?

Yeah, so we only clear that bit when at 'unlock' we find there are no
more pending waiters, so if the last unlock still had a waiter, we'll
leave the bit set. So its entirely reasonable to still have it set when
we free a page etc..
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux