svn commit: r249265 - in head/sys: amd64/include arm/include i386/include ia64/include mips/include powerpc/include sparc64/include sys

[Gleb Smirnoff]

On Mon, Apr 08, 2013 at 03:41:27PM -0400, John Baldwin wrote:
J> On Monday, April 08, 2013 3:19:10 pm Gleb Smirnoff wrote:
J> > Author: glebius
J> > Date: Mon Apr  8 19:19:10 2013
J> > New Revision: 249265
J> > URL: http://svnweb.freebsd.org/changeset/base/249265
J> > 
J> > Log:
J> >   Merge from projects/counters:
J> >   
J> >     Pad struct pcpu so that its size is denominator of PAGE_SIZE. This
J> >   is done to reduce memory waste in UMA_PCPU_ZONE zones.
J> >   
J> >   Sponsored by:	Nginx, Inc.
J> > 
J> > Modified: head/sys/sys/pcpu.h
J> > 
J> ==============================================================================
J> > --- head/sys/sys/pcpu.h	Mon Apr  8 19:10:45 2013	(r249264)
J> > +++ head/sys/sys/pcpu.h	Mon Apr  8 19:19:10 2013	(r249265)
J> > @@ -180,6 +180,14 @@ struct pcpu {
J> >  	PCPU_MD_FIELDS;
J> >  } __aligned(CACHE_LINE_SIZE);
J> 
J> Why not change this to be PAGE_SIZE rather than putting explicit padding in 
J> all the pcpu fields?  That would seem to be more maintainable.

Because it can be smaller than PAGE_SIZE. Two times smaller, four times smaller.

-- 
Totus tuus, Glebius.