Re: kern/57558: pgdaemon 100% busy - no scanning (ZFS case)

[Frank Kardel <kardel%netbsd.org@localhost>]

The following reply was made to PR kern/57558; it has been noted by GNATS.

From: Frank Kardel <kardel%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/57558: pgdaemon 100% busy - no scanning (ZFS case)
Date: Sun, 5 May 2024 10:03:38 +0200

 On 05/05/24 08:50, Michael van Elst wrote:
 >   
 >   I just have no reliable test case to verify that it changes
 >   the behaviour.
 >   
 >   
 As for testing you could use the D-Script
 sdt:::arc-available_memory
 {
            printf("mem = %d, reason = %d", arg0, arg1);
 }
 
 mem is positive when arc_available_memory thinks the is memory 
 (prohibits the reclaimthread to run even when triggered).
 mem is negative when memory should be freed giving the negative amount 
 to be freed.
 reason is the cause for the memory decision.
 reason is
 typedef enum free_memory_reason_t {
          FMR_UNKNOWN,
          FMR_NEEDFREE,
          FMR_LOTSFREE,
          FMR_SWAPFS_MINFREE,
          FMR_PAGES_PP_MAXIMUM,
          FMR_HEAP_ARENA,
          FMR_ZIO_ARENA,
          FMR_ZIO_FRAG,
 } free_memory_reason_t;
 
 Test case would be any large ZFS write/read operations.
 If you see 1 as cause it is the startvation guard fix.
 
 -Frank