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Date: Sun, 5 Feb 2017 13:03:08 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mateusz Guzik <mjg@FreeBSD.org>, src-committers@freebsd.org,
 svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject: Re: svn commit: r313275 - in head/sys: kern sys
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On Sun, Feb 05, 2017 at 11:01:28AM +0100, Mateusz Guzik wrote:

> On Sun, Feb 05, 2017 at 01:00:11PM +0300, Slawa Olhovchenkov wrote:
> > On Sun, Feb 05, 2017 at 08:04:12AM +0000, Mateusz Guzik wrote:
> > 
> > > Author: mjg
> > > Date: Sun Feb  5 08:04:11 2017
> > > New Revision: 313275
> > > URL: https://svnweb.freebsd.org/changeset/base/313275
> > > 
> > > Log:
> > >   mtx: move lockstat handling out of inline primitives
> > >   
> > >   Lockstat requires checking if it is enabled and if so, calling a 6 argument
> > >   function. Further, determining whether to call it on unlock requires
> > >   pre-reading the lock value.
> > >   
> > >   This is problematic in at least 3 ways:
> > >   - more branches in the hot path than necessary
> > >   - additional cacheline ping pong under contention
> > >   - bigger code
> > >   
> > >   Instead, check first if lockstat handling is necessary and if so, just fall
> > >   back to regular locking routines. For this purpose a new macro is introduced
> > >   (LOCKSTAT_PROFILE_ENABLED).
> > >   
> > >   LOCK_PROFILING uninlines all primitives. Fold in the current inline lock
> > >   variant into the _mtx_lock_flags to retain the support. With this change
> > >   the inline variants are not used when LOCK_PROFILING is defined and thus
> > >   can ignore its existence.
> > >   
> > >   This results in:
> > >      text	   data	    bss	    dec	    hex	filename
> > >   22259667	1303208	4994976	28557851	1b3c21b	kernel.orig
> > >   21797315	1303208	4994976	28095499	1acb40b	kernel.patched
> > >   
> > >   i.e. about 3% reduction in text size.
> > >   
> > >   A remaining action is to remove spurious arguments for internal kernel
> > >   consumers.
> > 
> > Do you planed MFC all of this?
> 
> Yes, around march.

Thanks!