On Fri, Aug 21, 2020 at 9:40 PM Philippe Mathieu-Daudé <phi...@redhat.com> wrote:
> On 8/21/20 1:58 PM, Daniel P. Berrangé wrote: > > On Fri, Aug 21, 2020 at 11:41:26AM +0800, Jiachen Zhang wrote: > >> Due to the commit 65da4539803373ec4eec97ffc49ee90083e56efd, the O_DIRECT > >> open flag of guest applications will be discarded by virtiofsd. While > >> this behavior makes it consistent with the virtio-9p scheme when guest > >> applications using direct I/O, we no longer have any chance to bypass > >> the host page cache. > >> > >> Therefore, we add a flag 'allow_directio' to lo_data. If '-o > no_directio' > >> option is added, or none of '-o no_directio' or '-o allow_directio' is > >> added, the 'allow_directio' will be set to 0, and virtiofsd discards > >> O_DIRECT as before. If '-o allow_directio' is added to the stariting > >> command-line, 'allow_directio' will be set to 1, so that the O_DIRECT > >> flags will be retained and host page cache can be bypassed. > >> > >> Signed-off-by: Jiachen Zhang <zhangjiachen.jay...@bytedance.com> > >> --- > >> tools/virtiofsd/helper.c | 4 ++++ > >> tools/virtiofsd/passthrough_ll.c | 20 ++++++++++++++------ > >> 2 files changed, 18 insertions(+), 6 deletions(-) > >> > >> diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c > >> index 3105b6c23a..534ff52c64 100644 > >> --- a/tools/virtiofsd/helper.c > >> +++ b/tools/virtiofsd/helper.c > >> @@ -180,6 +180,10 @@ void fuse_cmdline_help(void) > >> " (0 leaves rlimit > unchanged)\n" > >> " default: min(1000000, > fs.file-max - 16384)\n" > >> " if the current > rlimit is lower\n" > >> + " -o allow_directio|no_directio\n" > >> + " retain/discard O_DIRECT > flags passed down\n" > >> + " to virtiofsd from guest > applications.\n" > >> + " default: no_directio\n" > >> ); > > > > The standard naming convention from existing options is to use > > $OPTNAME and no_$OPTNAME. > > > > IOW, don't use the "allow_" prefix. The options should be just > > "directio" and "no_directio" > > As we have 'max_idle_threads' (and not maxidlethreads), can we > use 'direct_io' instead? > > Thanks. I will split them in the next version. Jiachen > > > Regards, > > Daniel > > > >
