ZFS ARC and mmap/page cache coherency question

[Matthew Macy]

 ---- On Sun, 03 Jul 2016 08:43:19 -0700 Karl Denninger <karl at denninger.net> wrote ---- 
 >  
 > On 7/3/2016 02:45, Matthew Macy wrote: 
 > >          
 > >             Cedric greatly overstates the intractability of resolving it. Nonetheless, since the initial import very little has been done to improve integration, and I don't know of anyone who is up to the task taking an interest in it. Consequently, mmap() performance is likely "doomed" for the foreseeable future.-M----  
 >  
 > Wellllll.... 
 >  
 > I've done a fair bit of work here (see 
 > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594) and the 
 > political issues are at least as bad as the coding ones. 
 >  
 

Strictly speaking, the root of the problem is the ARC. Not ZFS per se. Have you ever tried disabling MFU caching to see how much worse LRU only is? I'm not really convinced the ARC's benefits justify its cost.

-M