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

[Slawa Olhovchenkov]

On Tue, Nov 18, 2014 at 02:57:53PM -0800, Xin Li wrote:

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> On 11/18/14 14:00, Slawa Olhovchenkov wrote:
> > 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.
> 
> FWIW: It can be safely decreased: the ability to read such pool is
> maintained.
> 
> > 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)
> 
> That's true, but not free.  I don't think we have carefully evaluated
> the situation (and possible mitigation measures, like, do we need to
> make some improvements to the slab allocator?  It's never exposed to
> workload like this before, etc.), and people tend to make uninformed
> changes all the times (a lot of FreeBSD tuning guide gives wrong
> instructions).

Now I start production with raidz1 and recordsize 2MB.

> >> Requested by:	Slawa Olhovchenkov <slw zxy spb ru> MFC after:	2
> >> weeks
> > 
> > Thanks, can you allow RW?
> 
> Sure, done in 274681.
> 
> I didn't do it at the beginning because I don't think it's a good idea
> to make it easy for users to fiddle with it, and power users who
> actually need to tweak do not change it often.  But you are right
> there is no real technical reason not to allow read-write.

Thanks, just bad if required reboot creating zfs set with >1MB
recordsize. At this point site may be in prodation, for example.


> >> 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) \ { \ 
> >> _______________________________________________ 
> >> svn-src-all at freebsd.org mailing list 
> >> http://lists.freebsd.org/mailman/listinfo/svn-src-all To
> >> unsubscribe, send any mail to
> >> "svn-src-all-unsubscribe at freebsd.org"
> 
> 
> - -- 
> Xin LI <delphij at delphij.net>    https://www.delphij.net/
> FreeBSD - The Power to Serve!           Live free or die
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