| Message ID | 20200730010206.47051-1-jingqi.liu@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | docs/nvdimm: add 'pmem=on' for the device dax backend file | expand |
> At the end of live migration, QEMU uses msync() to flush the data to > the backend storage. When the backend file is a character device dax, > the pages explicitly avoid the page cache. It will return failure from msync(). > The following warning is output. > > "warning: qemu_ram_msync: failed to sync memory range“ > > So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: > > -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Jingqi Liu <jingqi.liu@intel.com> > --- > docs/nvdimm.txt | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt > index c2c6e441b3..31048aff5e 100644 > --- a/docs/nvdimm.txt > +++ b/docs/nvdimm.txt > @@ -243,6 +243,13 @@ use the QEMU command line: > > -object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on > > +At the end of live migration, QEMU uses msync() to flush the data to the > +backend storage. When the backend file is a character device dax, the pages > +explicitly avoid the page cache. It will return failure from msync(). > +So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: > + > + -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G > + > References > ---------- > > -- Good to document this. Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> > 2.17.1 > >
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt index c2c6e441b3..31048aff5e 100644 --- a/docs/nvdimm.txt +++ b/docs/nvdimm.txt @@ -243,6 +243,13 @@ use the QEMU command line: -object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on +At the end of live migration, QEMU uses msync() to flush the data to the +backend storage. When the backend file is a character device dax, the pages +explicitly avoid the page cache. It will return failure from msync(). +So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: + + -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G + References ----------
At the end of live migration, QEMU uses msync() to flush the data to the backend storage. When the backend file is a character device dax, the pages explicitly avoid the page cache. It will return failure from msync(). The following warning is output. "warning: qemu_ram_msync: failed to sync memory range“ So we add 'pmem=on' to avoid calling msync(), use the QEMU command line: -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Jingqi Liu <jingqi.liu@intel.com> --- docs/nvdimm.txt | 7 +++++++ 1 file changed, 7 insertions(+)