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

[Daniel P . Berrangé]

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 ?

> 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


Regards,
Daniel
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