Messages in this thread | | | Date | Thu, 22 Aug 2013 15:33:32 +0000 | From | Thavatchai Makphaibulchoke <> | Subject | Re: [PATCH v2 1/2] mbcache: decoupling the locking of local from global data |
| |
Thanks for the comments.
On 08/22/2013 04:53 PM, Linus Torvalds wrote: > > Please don't do these ugly and pointless preprocessor macro expanders > that hide what the actual operation is. > > The DEBUG case seems to be just for your own testing anyway, so even > that shouldn't exist in the merged version. >
Sorry, will clean them all up.
> > And this is really ugly. Again it's also then hidden behind the ugly macro. > > First off, the thousand-time retry seems completely excessive. Does it > actually need any retry AT ALL? If the hash entry changes, either you > should retry forever, or if you feel that can result in livelocks > (fair enough) and you need a fallback case to a bigger lock, then why > not just do the fallback immediately? > > More importantly, regardless of that retry issue, this seems to be > abstracted at the wrong level, resulting in every single user of this > repeating the same complex and hard-to-understand incantation: >
Looks like this is a misjudgement on my part. There is really no need to guard against mb_cache_entry from moving to a different hash chain, as the shrinking and allocation function already protecting against each other thorugh mb_cache_spinlock. The retry is not needed.
> > where the only difference is that the last one doesn't unlock > afterwards because it runs in a loop with that LRU list lock held. > Ugh.
Followed the above logic, all these pieces of code are also not necessary and could be just a simple unhash, as the original.
> > The locking logic also isn't explained anywhere, making the > hard-to-read code even harder to read.
Will add comment, explaining the locking logic.
> > Linus >
Thanks, Mak.
| |