Date: Wed, 4 Dec 2019 22:12:09 -0700 From: Warner Losh <imp@bsdimp.com> To: Ravi Pokala <rpokala@freebsd.org> Cc: Alexander Motin <mav@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r355412 - head/sys/geom Message-ID: <CANCZdfooav7V0Yci8Nta1VAbMtnwMsqwdMEH=f3dHyUVw6YDAg@mail.gmail.com> In-Reply-To: <516874DA-E57F-4EAA-852B-1129A95BB998@panasas.com> References: <201912050452.xB54qKV0080126@repo.freebsd.org> <516874DA-E57F-4EAA-852B-1129A95BB998@panasas.com>
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On Wed, Dec 4, 2019, 10:01 PM Ravi Pokala <rpokala@freebsd.org> wrote: > -----Original Message----- > From: <owner-src-committers@freebsd.org> on behalf of Alexander Motin > <mav@FreeBSD.org> > Date: 2019-12-04, Wednesday at 20:52 > To: <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, < > svn-src-head@freebsd.org> > Subject: svn commit: r355412 - head/sys/geom > > Author: mav > Date: Thu Dec 5 04:52:19 2019 > New Revision: 355412 > URL: https://svnweb.freebsd.org/changeset/base/355412 > > Log: > Wrap g_trace() into a macro to avoid unneeded calls. > > In most cases with debug disabled this function does nothing, but > argument > passing and the call still cost measurable time due to cache misses, > etc. > > Hi Alexander, > > I'm having trouble understanding this change, on a few levels. > > - Why did you add parentheses around the function declaration and > definition? > To prevent macro expansion. - How can that function with that name co-exist with a macro of the same > name? > See above. - Isn't the "g_debugflags" test in geom_dump.c:g_trace() now redundant? > I think so... - Why not simply convert geom_dump.c:g_trace() into a 'static inline' in > geom.h, and not have to bother with the macro at all? > I'd have done that :) you wouldn't have that weird (corner) of the language exposed... but the static inline might have been bigger... Warner What am I missing? > > Thanks, > > Ravi (rpokala@) > > MFC after: 2 weeks > Sponsored by: iXsystems, Inc. > > Modified: > head/sys/geom/geom.h > head/sys/geom/geom_dump.c > > Modified: head/sys/geom/geom.h > > ============================================================================== > --- head/sys/geom/geom.h Thu Dec 5 04:18:22 2019 (r355411) > +++ head/sys/geom/geom.h Thu Dec 5 04:52:19 2019 (r355412) > @@ -255,11 +255,15 @@ void g_dev_physpath_changed(void); > struct g_provider *g_dev_getprovider(struct cdev *dev); > > /* geom_dump.c */ > -void g_trace(int level, const char *, ...); > +void (g_trace)(int level, const char *, ...) __printflike(2, 3); > # define G_T_TOPOLOGY 1 > # define G_T_BIO 2 > # define G_T_ACCESS 4 > - > +extern int g_debugflags; > +#define g_trace(level, fmt, ...) do { \ > + if (__predict_false(g_debugflags & (level))) \ > + (g_trace)(level, fmt, ## __VA_ARGS__); \ > +} while (0) > > /* geom_event.c */ > typedef void g_event_t(void *, int flag); > > Modified: head/sys/geom/geom_dump.c > > ============================================================================== > --- head/sys/geom/geom_dump.c Thu Dec 5 04:18:22 2019 > (r355411) > +++ head/sys/geom/geom_dump.c Thu Dec 5 04:52:19 2019 > (r355412) > @@ -319,7 +319,7 @@ g_confxml(void *p, int flag) > } > > void > -g_trace(int level, const char *fmt, ...) > +(g_trace)(int level, const char *fmt, ...) > { > va_list ap; > > > > >
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