Re: [PATCH 058/104] virtiofsd: print log only when priority is high enough

[Dr. David Alan Gilbert]

* Daniel P. Berrangé (address@hidden) wrote:
> On Thu, Dec 12, 2019 at 04:38:18PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: Eryu Guan <address@hidden>
> > 
> > Introduce "-o log_level=" command line option to specify current log
> > level (priority), valid values are "debug info warn err", e.g.
> > 
> >     ./virtiofsd -o log_level=debug ...
> > 
> > So only log priority higher than "debug" will be printed to
> > stderr/syslog. And the default level is info.
> > 
> > The "-o debug"/"-d" options are kept, and imply debug log level.
> > 
> > Signed-off-by: Eryu Guan <address@hidden>
> > dgilbert: Reworked for libfuse's log_func
> > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > ---
> >  tools/virtiofsd/fuse_log.c       |   4 ++
> >  tools/virtiofsd/fuse_lowlevel.c  |  75 ++++++++------------
> >  tools/virtiofsd/fuse_lowlevel.h  |   1 +
> >  tools/virtiofsd/helper.c         |  10 ++-
> >  tools/virtiofsd/passthrough_ll.c | 118 +++++++++++++------------------
> >  5 files changed, 92 insertions(+), 116 deletions(-)
> 
> > diff --git a/tools/virtiofsd/fuse_log.c b/tools/virtiofsd/fuse_log.c
> > index 11345f9ec8..79a18a7aaa 100644
> > --- a/tools/virtiofsd/fuse_log.c
> > +++ b/tools/virtiofsd/fuse_log.c
> > @@ -8,6 +8,10 @@
> >   * See the file COPYING.LIB
> >   */
> >  
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <stdarg.h>
> > +#include <syslog.h>
> >  #include "fuse_log.h"
> >  
> >  #include <stdarg.h>
> 
> Why do we need to add these headers if there are no code changes in this
> file ?

Thanks, those are left overs from an earlier version; I've deleted them now.

> > diff --git a/tools/virtiofsd/fuse_lowlevel.c 
> > b/tools/virtiofsd/fuse_lowlevel.c
> > index f3c8bdf7cb..0abb369b3d 100644
> > --- a/tools/virtiofsd/fuse_lowlevel.c
> > +++ b/tools/virtiofsd/fuse_lowlevel.c
> > @@ -158,19 +158,17 @@ static int fuse_send_msg(struct fuse_session *se, 
> > struct fuse_chan *ch,
> >      struct fuse_out_header *out = iov[0].iov_base;
> >  
> >      out->len = iov_length(iov, count);
> > -    if (se->debug) {
> > -        if (out->unique == 0) {
> > -            fuse_log(FUSE_LOG_DEBUG, "NOTIFY: code=%d length=%u\n", 
> > out->error,
> > -                     out->len);
> > -        } else if (out->error) {
> > -            fuse_log(FUSE_LOG_DEBUG,
> > -                     "   unique: %llu, error: %i (%s), outsize: %i\n",
> > -                     (unsigned long long)out->unique, out->error,
> > -                     strerror(-out->error), out->len);
> > -        } else {
> > -            fuse_log(FUSE_LOG_DEBUG, "   unique: %llu, success, outsize: 
> > %i\n",
> > -                     (unsigned long long)out->unique, out->len);
> > -        }
> > +    if (out->unique == 0) {
> > +        fuse_log(FUSE_LOG_DEBUG, "NOTIFY: code=%d length=%u\n", out->error,
> > +                 out->len);
> > +    } else if (out->error) {
> > +        fuse_log(FUSE_LOG_DEBUG,
> > +                 "   unique: %llu, error: %i (%s), outsize: %i\n",
> > +                 (unsigned long long)out->unique, out->error,
> > +                 strerror(-out->error), out->len);
> > +    } else {
> > +        fuse_log(FUSE_LOG_DEBUG, "   unique: %llu, success, outsize: %i\n",
> > +                 (unsigned long long)out->unique, out->len);
> >      }
> 
> Removing all the 'if (se->debug)' checks means that we take the
> performance hit of calling many logging functions in the common
> case where debug is disabled. Hopefully 'fuse_log' is smart
> enough to avoid printf formatting of the msg + args unless
> it is actually goiing to output the message

It is; we go through fuse_log (fuse_log.c an imported file) that just
does the va_start and then calls the log_func that was set later in this
patch and the first thing it does is check the level and exit.

Dave

> 
> 
> Regards,
> Daniel
> -- 
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--
Dr. David Alan Gilbert / address@hidden / Manchester, UK