svn commit: r274673 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Slawa Olhovchenkov]

On Tue, Nov 18, 2014 at 06:40:02PM +0000, Xin LI wrote:

> Author: delphij
> Date: Tue Nov 18 18:40:01 2014
> New Revision: 274673
> URL: https://svnweb.freebsd.org/changeset/base/274673
> 
> Log:
>   Allow tuning zfs_max_recordsize via loader tunable.  Tuning is NOT
>   recommended.

This is not tuning, this is simple guard.
And can be safe changed (incrased, at the least) in any time.
For some workload optimal is maximum, i.e. 16MB.
May be better comment: increasing this value required strong
understaning after-effects of increasing memory consumption and
bulk data transfers. (sorry for english)

>   Requested by:	Slawa Olhovchenkov <slw zxy spb ru>
>   MFC after:	2 weeks

Thanks, can you allow RW?

> Modified:
>   head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
> 
> Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c
> ==============================================================================
> --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Tue Nov 18 18:03:40 2014	(r274672)
> +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c	Tue Nov 18 18:40:01 2014	(r274673)
> @@ -51,6 +51,8 @@
>  #include <sys/dsl_userhold.h>
>  #include <sys/dsl_bookmark.h>
>  
> +SYSCTL_DECL(_vfs_zfs);
> +
>  /*
>   * The SPA supports block sizes up to 16MB.  However, very large blocks
>   * can have an impact on i/o latency (e.g. tying up a spinning disk for
> @@ -61,6 +63,9 @@
>   * of this setting.
>   */
>  int zfs_max_recordsize = 1 * 1024 * 1024;
> +SYSCTL_INT(_vfs_zfs, OID_AUTO, max_recordsize, CTLFLAG_RDTUN,
> +    &zfs_max_recordsize, 0,
> +    "Maximum block size.  Expect dragons when tuning this.");
>  
>  #define	SWITCH64(x, y) \
>  	{ \
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