| Message ID | 20180216131625.9639-4-dgilbert@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Feb 16, 2018 at 01:15:59PM +0000, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > Use a flag on the RAMBlock to state whether it has the > UFFDIO_ZEROPAGE capability, use it when it's available. > > This allows the use of postcopy on tmpfs as well as hugepage > backed files. > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > --- > exec.c | 15 +++++++++++++++ > include/exec/cpu-common.h | 3 +++ > migration/postcopy-ram.c | 13 ++++++++++--- > 3 files changed, 28 insertions(+), 3 deletions(-) > > diff --git a/exec.c b/exec.c > index 0ec73bc917..1dc15298c2 100644 > --- a/exec.c > +++ b/exec.c > @@ -99,6 +99,11 @@ static MemoryRegion io_mem_unassigned; > */ > #define RAM_RESIZEABLE (1 << 2) > > +/* UFFDIO_ZEROPAGE is available on this RAMBlock to atomically > + * zero the page and wake waiting processes. > + * (Set during postcopy) > + */ > +#define RAM_UF_ZEROPAGE (1 << 3) > #endif > > #ifdef TARGET_PAGE_BITS_VARY > @@ -1767,6 +1772,16 @@ bool qemu_ram_is_shared(RAMBlock *rb) > return rb->flags & RAM_SHARED; > } > > +bool qemu_ram_is_uf_zeroable(RAMBlock *rb) > +{ > + return rb->flags & RAM_UF_ZEROPAGE; > +} > + > +void qemu_ram_set_uf_zeroable(RAMBlock *rb) > +{ > + rb->flags |= RAM_UF_ZEROPAGE; > +} > + > /* Called with iothread lock held. */ > void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState *dev) > { > diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h > index 0d861a6289..24d335f95d 100644 > --- a/include/exec/cpu-common.h > +++ b/include/exec/cpu-common.h > @@ -73,6 +73,9 @@ void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev); > void qemu_ram_unset_idstr(RAMBlock *block); > const char *qemu_ram_get_idstr(RAMBlock *rb); > bool qemu_ram_is_shared(RAMBlock *rb); > +bool qemu_ram_is_uf_zeroable(RAMBlock *rb); > +void qemu_ram_set_uf_zeroable(RAMBlock *rb); > + > size_t qemu_ram_pagesize(RAMBlock *block); > size_t qemu_ram_pagesize_largest(void); > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index bec6c2c66b..6297979700 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -490,6 +490,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, > error_report("%s userfault: Region doesn't support COPY", __func__); > return -1; > } > + if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) { > + RAMBlock *rb = qemu_ram_block_by_name(block_name); > + qemu_ram_set_uf_zeroable(rb); > + } So the zeroable flag is only set after a listening operation of postcopy migration. One thing I am a bit worried is that if someone else wants to use the flag for a RAMBlock he/she may not notice this. Say, qemu_ram_is_uf_zeroable() is not valid if there is no such an incoming postcopy migration. Maybe worth add a comment in the flag definition about this? Not a big deal (considering that I see no potential QEMU user for userfaultfd in short peroid), so no matter what: Reviewed-by: Peter Xu <peterx@redhat.com> > > return 0; > } > @@ -699,11 +703,14 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, > int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, > RAMBlock *rb) > { > + size_t pagesize = qemu_ram_pagesize(rb); > trace_postcopy_place_page_zero(host); > > - if (qemu_ram_pagesize(rb) == getpagesize()) { > - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, getpagesize(), > - rb)) { > + /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE > + * but it's not available for everything (e.g. hugetlbpages) > + */ > + if (qemu_ram_is_uf_zeroable(rb)) { > + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) { > int e = errno; > error_report("%s: %s zero host: %p", > __func__, strerror(e), host); > -- > 2.14.3 >
* Peter Xu (peterx@redhat.com) wrote: > On Fri, Feb 16, 2018 at 01:15:59PM +0000, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > > > Use a flag on the RAMBlock to state whether it has the > > UFFDIO_ZEROPAGE capability, use it when it's available. > > > > This allows the use of postcopy on tmpfs as well as hugepage > > backed files. > > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > > --- > > exec.c | 15 +++++++++++++++ > > include/exec/cpu-common.h | 3 +++ > > migration/postcopy-ram.c | 13 ++++++++++--- > > 3 files changed, 28 insertions(+), 3 deletions(-) > > > > diff --git a/exec.c b/exec.c > > index 0ec73bc917..1dc15298c2 100644 > > --- a/exec.c > > +++ b/exec.c > > @@ -99,6 +99,11 @@ static MemoryRegion io_mem_unassigned; > > */ > > #define RAM_RESIZEABLE (1 << 2) > > > > +/* UFFDIO_ZEROPAGE is available on this RAMBlock to atomically > > + * zero the page and wake waiting processes. > > + * (Set during postcopy) > > + */ > > +#define RAM_UF_ZEROPAGE (1 << 3) > > #endif > > > > #ifdef TARGET_PAGE_BITS_VARY > > @@ -1767,6 +1772,16 @@ bool qemu_ram_is_shared(RAMBlock *rb) > > return rb->flags & RAM_SHARED; > > } > > > > +bool qemu_ram_is_uf_zeroable(RAMBlock *rb) > > +{ > > + return rb->flags & RAM_UF_ZEROPAGE; > > +} > > + > > +void qemu_ram_set_uf_zeroable(RAMBlock *rb) > > +{ > > + rb->flags |= RAM_UF_ZEROPAGE; > > +} > > + > > /* Called with iothread lock held. */ > > void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState *dev) > > { > > diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h > > index 0d861a6289..24d335f95d 100644 > > --- a/include/exec/cpu-common.h > > +++ b/include/exec/cpu-common.h > > @@ -73,6 +73,9 @@ void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev); > > void qemu_ram_unset_idstr(RAMBlock *block); > > const char *qemu_ram_get_idstr(RAMBlock *rb); > > bool qemu_ram_is_shared(RAMBlock *rb); > > +bool qemu_ram_is_uf_zeroable(RAMBlock *rb); > > +void qemu_ram_set_uf_zeroable(RAMBlock *rb); > > + > > size_t qemu_ram_pagesize(RAMBlock *block); > > size_t qemu_ram_pagesize_largest(void); > > > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > > index bec6c2c66b..6297979700 100644 > > --- a/migration/postcopy-ram.c > > +++ b/migration/postcopy-ram.c > > @@ -490,6 +490,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, > > error_report("%s userfault: Region doesn't support COPY", __func__); > > return -1; > > } > > + if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) { > > + RAMBlock *rb = qemu_ram_block_by_name(block_name); > > + qemu_ram_set_uf_zeroable(rb); > > + } > > So the zeroable flag is only set after a listening operation of > postcopy migration. One thing I am a bit worried is that if someone > else wants to use the flag for a RAMBlock he/she may not notice this. > Say, qemu_ram_is_uf_zeroable() is not valid if there is no such an > incoming postcopy migration. Yes, the problem is you don't get to know until you register it with userfault. > Maybe worth add a comment in the flag definition about this? Yes, I've added: /* Note: Only set at the start of postcopy */ above the qemu_ram_is_uf_zeroable() defintiion; also see the existing '(Set during postcopy)' comment above the #define. > Not a big deal (considering that I see no potential QEMU user for > userfaultfd in short peroid), so no matter what: > > Reviewed-by: Peter Xu <peterx@redhat.com> Thanks. Dave > > > > > return 0; > > } > > @@ -699,11 +703,14 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, > > int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, > > RAMBlock *rb) > > { > > + size_t pagesize = qemu_ram_pagesize(rb); > > trace_postcopy_place_page_zero(host); > > > > - if (qemu_ram_pagesize(rb) == getpagesize()) { > > - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, getpagesize(), > > - rb)) { > > + /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE > > + * but it's not available for everything (e.g. hugetlbpages) > > + */ > > + if (qemu_ram_is_uf_zeroable(rb)) { > > + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) { > > int e = errno; > > error_report("%s: %s zero host: %p", > > __func__, strerror(e), host); > > -- > > 2.14.3 > > > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/exec.c b/exec.c index 0ec73bc917..1dc15298c2 100644 --- a/exec.c +++ b/exec.c @@ -99,6 +99,11 @@ static MemoryRegion io_mem_unassigned; */ #define RAM_RESIZEABLE (1 << 2) +/* UFFDIO_ZEROPAGE is available on this RAMBlock to atomically + * zero the page and wake waiting processes. + * (Set during postcopy) + */ +#define RAM_UF_ZEROPAGE (1 << 3) #endif #ifdef TARGET_PAGE_BITS_VARY @@ -1767,6 +1772,16 @@ bool qemu_ram_is_shared(RAMBlock *rb) return rb->flags & RAM_SHARED; } +bool qemu_ram_is_uf_zeroable(RAMBlock *rb) +{ + return rb->flags & RAM_UF_ZEROPAGE; +} + +void qemu_ram_set_uf_zeroable(RAMBlock *rb) +{ + rb->flags |= RAM_UF_ZEROPAGE; +} + /* Called with iothread lock held. */ void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState *dev) { diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h index 0d861a6289..24d335f95d 100644 --- a/include/exec/cpu-common.h +++ b/include/exec/cpu-common.h @@ -73,6 +73,9 @@ void qemu_ram_set_idstr(RAMBlock *block, const char *name, DeviceState *dev); void qemu_ram_unset_idstr(RAMBlock *block); const char *qemu_ram_get_idstr(RAMBlock *rb); bool qemu_ram_is_shared(RAMBlock *rb); +bool qemu_ram_is_uf_zeroable(RAMBlock *rb); +void qemu_ram_set_uf_zeroable(RAMBlock *rb); + size_t qemu_ram_pagesize(RAMBlock *block); size_t qemu_ram_pagesize_largest(void); diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index bec6c2c66b..6297979700 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -490,6 +490,10 @@ static int ram_block_enable_notify(const char *block_name, void *host_addr, error_report("%s userfault: Region doesn't support COPY", __func__); return -1; } + if (reg_struct.ioctls & ((__u64)1 << _UFFDIO_ZEROPAGE)) { + RAMBlock *rb = qemu_ram_block_by_name(block_name); + qemu_ram_set_uf_zeroable(rb); + } return 0; } @@ -699,11 +703,14 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, RAMBlock *rb) { + size_t pagesize = qemu_ram_pagesize(rb); trace_postcopy_place_page_zero(host); - if (qemu_ram_pagesize(rb) == getpagesize()) { - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, getpagesize(), - rb)) { + /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE + * but it's not available for everything (e.g. hugetlbpages) + */ + if (qemu_ram_is_uf_zeroable(rb)) { + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, NULL, pagesize, rb)) { int e = errno; error_report("%s: %s zero host: %p", __func__, strerror(e), host);