re: Reclaiming vnodes

[matthew green <mrg%eterna.com.au@localhost>]

i'm still not entirely sure what the point of this patch is.  i
understand it helps zfs, but i don't understand why or how. i'm
also curious what sort of testing you've done.  i do not believe
that testing in qemu is sufficient.  how does it affect systems
that recycle vnodes a lot, such as older systems running a build?  

please get a bunch more testing done with this before commiting,
comparing loads that *would* have led to recycle with the old
scheme.

some comments no the code itself:
   
   --- kern/vfs_subr.c  26 Jun 2009 18:58:14 -0000      1.383
   +++ kern/vfs_subr.c  14 Sep 2009 00:57:28 -0000
   @@ -90,6 +90,8 @@
     * value can be done using atomic operations, without the interlock held.
     */
    
   +#define QUEUEDEBUG  1
   +

please make sure you do not commit this.

   Index: sys/param.h
   ===================================================================
   RCS file: /cvsroot/src/sys/sys/param.h,v
   retrieving revision 1.350
   diff -u -p -r1.350 param.h
   --- sys/param.h      29 Jun 2009 05:47:35 -0000      1.350
   +++ sys/param.h      14 Sep 2009 00:57:30 -0000
   @@ -154,6 +154,12 @@
    #ifndef BUFCACHE_VA_MAXPCT
    #define     BUFCACHE_VA_MAXPCT      20
    #endif
   +#ifndef VNODES_NUM_LOWAT
   +#define VNODES_NUM_LOWAT        95          /* Min num in % of vnodes in 
freelist */
   +#endif
   +#ifndef VNODES_NUM_HIWAT
   +#define VNODES_NUM_HIWAT        99          /* Max num in  % of vnodes in 
freelist */
   +#endif
    #define     VNODE_COST      2048                    /* assumed space in 
bytes */
    #endif /* _KERNEL */
    
   Index: conf/param.c
   ===================================================================
   RCS file: /cvsroot/src/sys/conf/param.c,v
   retrieving revision 1.62
   diff -u -p -r1.62 param.c
   --- conf/param.c     3 May 2009 21:25:44 -0000       1.62
   +++ conf/param.c     14 Sep 2009 00:57:31 -0000
   @@ -119,6 +119,8 @@ int      tickadj = (240000 / (60 * HZ)) ? (24
    int rtc_offset = RTC_OFFSET;
    int maxproc = NPROC;
    int desiredvnodes = NVNODE;
   +int     vreclaim_hiwat = ((NVNODE % 100) * VNODES_NUM_HIWAT);
   +int     vreclaim_lowat = ((NVNODE % 100) * VNODES_NUM_LOWAT);
    u_int       maxfiles = MAXFILES;
    int fscale = FSCALE;        /* kernel uses `FSCALE', user uses `fscale' */
    int maxexec = MAXEXEC;      /* max number of concurrent exec() calls */

any particular reason to change param.h/param.c for this?
please put them somewhere less generic.  maybe vfs_subr.c
and sys/vnode.h?

also, please put "extern"s for them in a header file and not in
several source files.  ie:

+++ kern/init_sysctl.c  14 Sep 2009 00:57:25 -0000
+++ kern/vfs_subr.c     14 Sep 2009 00:57:28 -0000
+++ kern/init_main.c    14 Sep 2009 00:57:29 -0000

these files shouldn't need to 'extern' a variable, it should
come from a header file.


thanks.

.mrg.