ZFS write stalls (starving reads) and tuning zfs_write_limit_override

[Sam Fourman Jr.]

> Hi,
>
> What I posted was not a patch, but just the lines need to be added to dsl_pool.c and it should work for either 8 or CURRENT.
> Here is a patch for 8-STABLE that I just generated, can you try that one (pasting in the email in case the email eats the attachment
> ):
>
> --- .zfs/snapshot/orig/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c        2009-08-24 07:30:23.677549074 +0300
> +++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c   2010-02-19 09:17:50.058020997 +0200
> @@ -47,6 +47,11 @@
>  uint64_t zfs_write_limit_override = 0;
>  extern uint64_t zfs_write_limit_min;
>
> +SYSCTL_DECL(_vfs_zfs);
> +TUNABLE_ULONG("vfs.zfs.write_limit_override", &zfs_write_limit_override);
> +SYSCTL_ULONG(_vfs_zfs, OID_AUTO, zfs_write_limit_override, CTLFLAG_RW, &zfs_write_limit_override, 0,
> +    "Override maximum TXG size");
> +
>  kmutex_t zfs_write_limit_lock;
>
>  static pgcnt_t old_physmem = 0;
>


what setting have you found to be the best for zfs_write_limit_override ?

Sam Fourman Jr.
Fourman Networks