[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v3 3/3] migration: add bitmap for received page
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v3 3/3] migration: add bitmap for received page |
Date: |
Fri, 23 Jun 2017 20:41:41 +0100 |
User-agent: |
Mutt/1.8.2 (2017-04-18) |
* Perevalov Alexey (address@hidden) wrote:
> On Fri, Jun 23, 2017 at 11:29:42AM +0100, Dr. David Alan Gilbert wrote:
> > * Alexey Perevalov (address@hidden) wrote:
> > > This patch adds ability to track down already received
> > > pages, it's necessary for calculation vCPU block time in
> > > postcopy migration feature, maybe for restore after
> > > postcopy migration failure.
> > > Also it's necessary to solve shared memory issue in
> > > postcopy livemigration. Information about received pages
> > > will be transferred to the software virtual bridge
> > > (e.g. OVS-VSWITCHD), to avoid fallocate (unmap) for
> > > already received pages. fallocate syscall is required for
> > > remmaped shared memory, due to remmaping itself blocks
> > > ioctl(UFFDIO_COPY, ioctl in this case will end with EEXIT
> > > error (struct page is exists after remmap).
> > >
> > > Bitmap is placed into RAMBlock as another postcopy/precopy
> > > related bitmaps.
> > >
> > > Signed-off-by: Alexey Perevalov <address@hidden>
> > > ---
> > > include/exec/ram_addr.h | 3 +++
> > > migration/migration.c | 1 +
> > > migration/postcopy-ram.c | 12 ++++++---
> > > migration/ram.c | 66
> > > +++++++++++++++++++++++++++++++++++++++++++++---
> > > migration/ram.h | 6 +++++
> > > 5 files changed, 82 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
> > > index 140efa8..67fbb39 100644
> > > --- a/include/exec/ram_addr.h
> > > +++ b/include/exec/ram_addr.h
> > > @@ -47,6 +47,8 @@ struct RAMBlock {
> > > * of the postcopy phase
> > > */
> > > unsigned long *unsentmap;
> > > + /* bitmap of already received pages in postcopy */
> > > + unsigned long *receivedmap;
> > > };
> > >
> > > static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
> > > @@ -60,6 +62,7 @@ static inline void *ramblock_ptr(RAMBlock *block,
> > > ram_addr_t offset)
> > > return (char *)block->host + offset;
> > > }
> > >
> > > +unsigned long int ramblock_recv_bitmap_offset(void *host_addr, RAMBlock
> > > *rb);
> > > long qemu_getrampagesize(void);
> > > unsigned long last_ram_page(void);
> > > RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr,
> > > diff --git a/migration/migration.c b/migration/migration.c
> > > index 71e38bc..53fbd41 100644
> > > --- a/migration/migration.c
> > > +++ b/migration/migration.c
> > > @@ -143,6 +143,7 @@ MigrationIncomingState
> > > *migration_incoming_get_current(void)
> > > qemu_mutex_init(&mis_current.rp_mutex);
> > > qemu_event_init(&mis_current.main_thread_load_event, false);
> > > once = true;
> > > + ramblock_recv_map_init();
> > > }
> > > return &mis_current;
> > > }
> > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > > index d1af2c1..5d2b92d 100644
> > > --- a/migration/postcopy-ram.c
> > > +++ b/migration/postcopy-ram.c
> > > @@ -562,8 +562,13 @@ int
> > > postcopy_ram_enable_notify(MigrationIncomingState *mis)
> > > }
> > >
> > > static int qemu_ufd_copy_ioctl(int userfault_fd, void *host_addr,
> > > - void *from_addr, uint64_t pagesize)
> > > + void *from_addr, uint64_t pagesize, RAMBlock *rb)
> > > {
> > > + /* received page isn't feature of blocktime calculation,
> > > + * it's more general entity, so keep it here,
> > > + * but gup betwean two following operation could be high,
> > > + * and in this case blocktime for such small interval will be lost */
> > > + ramblock_recv_bitmap_set(host_addr, rb);
> >
> > I have a fun problem here in my world with using the same bitmap for
> > shared memory with the vhost-user client; for that a set bit means
> > that the data has already arrived and we need to do a UFFDIO_WAKE on
> > the client;
> Do you mean vhost-user client?
Yes, I'm doing UFFDIO_WAKE calls on the userfault fd passed to me by
the client.
> > but that means we can't set the bit in this function until
> > the end after we've done the COPY/ZERO.
>
> I have the same problem, I described it to Peter, when he asked why
> ramblock_recv_bitmap_set should be closer to ioctl. But even such
> position doesn't solve that problem.
>
> I could repeat here, I'm sending that bitmap to vhost-user client, and
> it's possible situation when bitmap is set but page not yet copied.
> Did you faced that? Or just mention it as potential problem.
A similar problem; I've got the fault thread receiving a fault request
from the UFD, if the bit is set then it sends a WAKE, if it's not set
then it sends a request back to the source.
If we set the bit before the COPY/ZERO then I could send a WAKE too
early.
> If so, we could move ramblock_recv_bitmap_set after ioctl,
> but we chose that way to avoid situation when new page fault happening
> during ioctl or betwean ioctl and ramblock_recv_bitmap_set on the same vCPU.
> Or introduce 2 bitmap, copied/received.
It's a shame to need 2 bits. We shouldn't get another fault on the
same page, but I guess we can get it from another CPU on the same page
which hmm is the problem with the stats code.
Dave
> >
> > Dave
> >
> > > if (from_addr) {
> > > struct uffdio_copy copy_struct;
> > > copy_struct.dst = (uint64_t)(uintptr_t)host_addr;
> > > @@ -594,7 +599,7 @@ int postcopy_place_page(MigrationIncomingState *mis,
> > > void *host, void *from,
> > > * which would be slightly cheaper, but we'd have to be careful
> > > * of the order of updating our page state.
> > > */
> > > - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, from, pagesize)) {
> > > + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, from, pagesize,
> > > rb)) {
> > > int e = errno;
> > > error_report("%s: %s copy host: %p from: %p (size: %zd)",
> > > __func__, strerror(e), host, from, pagesize);
> > > @@ -616,7 +621,8 @@ int postcopy_place_page_zero(MigrationIncomingState
> > > *mis, void *host,
> > > trace_postcopy_place_page_zero(host);
> > >
> > > if (qemu_ram_pagesize(rb) == getpagesize()) {
> > > - if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, 0,
> > > getpagesize())) {
> > > + if (qemu_ufd_copy_ioctl(mis->userfault_fd, host, 0,
> > > getpagesize(),
> > > + rb)) {
> > > int e = errno;
> > > error_report("%s: %s zero host: %p",
> > > __func__, strerror(e), host);
> > > diff --git a/migration/ram.c b/migration/ram.c
> > > index f50479d..fad4dbf 100644
> > > --- a/migration/ram.c
> > > +++ b/migration/ram.c
> > > @@ -151,6 +151,41 @@ out:
> > > return ret;
> > > }
> > >
> > > +void ramblock_recv_map_init(void)
> > > +{
> > > + RAMBlock *rb;
> > > +
> > > + RAMBLOCK_FOREACH(rb) {
> > > + unsigned long pages;
> > > + pages = rb->max_length >> TARGET_PAGE_BITS;
> > > + assert(!rb->receivedmap);
> > > + rb->receivedmap = bitmap_new(pages);
> > > + }
> > > +}
> > > +
> > > +unsigned long int ramblock_recv_bitmap_offset(void *host_addr, RAMBlock
> > > *rb)
> > > +{
> > > + uint64_t host_addr_offset = (uint64_t)(uintptr_t)(host_addr
> > > + - (void
> > > *)rb->host);
> > > + return host_addr_offset >> TARGET_PAGE_BITS;
> > > +}
> > > +
> > > +int ramblock_recv_bitmap_test(void *host_addr, RAMBlock *rb)
> > > +{
> > > + return test_bit(ramblock_recv_bitmap_offset(host_addr, rb),
> > > + rb->receivedmap);
> > > +}
> > > +
> > > +void ramblock_recv_bitmap_set(void *host_addr, RAMBlock *rb)
> > > +{
> > > + set_bit_atomic(ramblock_recv_bitmap_offset(host_addr, rb),
> > > rb->receivedmap);
> > > +}
> > > +
> > > +void ramblock_recv_bitmap_clear(void *host_addr, RAMBlock *rb)
> > > +{
> > > + clear_bit(ramblock_recv_bitmap_offset(host_addr, rb),
> > > rb->receivedmap);
> > > +}
> > > +
> > > /*
> > > * An outstanding page request, on the source, having been received
> > > * and queued
> > > @@ -1773,6 +1808,18 @@ int
> > > ram_postcopy_send_discard_bitmap(MigrationState *ms)
> > > return ret;
> > > }
> > >
> > > +static void ramblock_recv_bitmap_clear_range(uint64_t start, size_t
> > > length,
> > > + RAMBlock *rb)
> > > +{
> > > + int i, range_count;
> > > + range_count = length >> TARGET_PAGE_BITS;
> > > + for (i = 0; i < range_count; i++) {
> > > + ramblock_recv_bitmap_clear((void *)((uint64_t)(intptr_t)rb->host
> > > +
> > > + start), rb);
> > > + start += TARGET_PAGE_SIZE;
> > > + }
> > > +}
> > > +
> > > /**
> > > * ram_discard_range: discard dirtied pages at the beginning of postcopy
> > > *
> > > @@ -1797,6 +1844,7 @@ int ram_discard_range(const char *rbname, uint64_t
> > > start, size_t length)
> > > goto err;
> > > }
> > >
> > > + ramblock_recv_bitmap_clear_range(start, length, rb);
> > > ret = ram_block_discard_range(rb, start, length);
> > >
> > > err:
> > > @@ -2324,8 +2372,14 @@ static int ram_load_setup(QEMUFile *f, void
> > > *opaque)
> > >
> > > static int ram_load_cleanup(void *opaque)
> > > {
> > > + RAMBlock *rb;
> > > xbzrle_load_cleanup();
> > > compress_threads_load_cleanup();
> > > +
> > > + RAMBLOCK_FOREACH(rb) {
> > > + g_free(rb->receivedmap);
> > > + rb->receivedmap = NULL;
> > > + }
> > > return 0;
> > > }
> > >
> > > @@ -2513,6 +2567,7 @@ static int ram_load(QEMUFile *f, void *opaque, int
> > > version_id)
> > > ram_addr_t addr, total_ram_bytes;
> > > void *host = NULL;
> > > uint8_t ch;
> > > + RAMBlock *rb;
> > >
> > > addr = qemu_get_be64(f);
> > > flags = addr & ~TARGET_PAGE_MASK;
> > > @@ -2520,15 +2575,15 @@ static int ram_load(QEMUFile *f, void *opaque,
> > > int version_id)
> > >
> > > if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE |
> > > RAM_SAVE_FLAG_COMPRESS_PAGE |
> > > RAM_SAVE_FLAG_XBZRLE)) {
> > > - RAMBlock *block = ram_block_from_stream(f, flags);
> > > + rb = ram_block_from_stream(f, flags);
> > >
> > > - host = host_from_ram_block_offset(block, addr);
> > > + host = host_from_ram_block_offset(rb, addr);
> > > if (!host) {
> > > error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
> > > ret = -EINVAL;
> > > break;
> > > }
> > > - trace_ram_load_loop(block->idstr, (uint64_t)addr, flags,
> > > host);
> > > + trace_ram_load_loop(rb->idstr, (uint64_t)addr, flags, host);
> > > }
> > >
> > > switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
> > > @@ -2582,10 +2637,12 @@ static int ram_load(QEMUFile *f, void *opaque,
> > > int version_id)
> > >
> > > case RAM_SAVE_FLAG_ZERO:
> > > ch = qemu_get_byte(f);
> > > + ramblock_recv_bitmap_set(host, rb);
> > > ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
> > > break;
> > >
> > > case RAM_SAVE_FLAG_PAGE:
> > > + ramblock_recv_bitmap_set(host, rb);
> > > qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
> > > break;
> > >
> > > @@ -2596,10 +2653,13 @@ static int ram_load(QEMUFile *f, void *opaque,
> > > int version_id)
> > > ret = -EINVAL;
> > > break;
> > > }
> > > +
> > > + ramblock_recv_bitmap_set(host, rb);
> > > decompress_data_with_multi_threads(f, host, len);
> > > break;
> > >
> > > case RAM_SAVE_FLAG_XBZRLE:
> > > + ramblock_recv_bitmap_set(host, rb);
> > > if (load_xbzrle(f, addr, host) < 0) {
> > > error_report("Failed to decompress XBZRLE page at "
> > > RAM_ADDR_FMT, addr);
> > > diff --git a/migration/ram.h b/migration/ram.h
> > > index c081fde..98d68df 100644
> > > --- a/migration/ram.h
> > > +++ b/migration/ram.h
> > > @@ -52,4 +52,10 @@ int ram_discard_range(const char *block_name, uint64_t
> > > start, size_t length);
> > > int ram_postcopy_incoming_init(MigrationIncomingState *mis);
> > >
> > > void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
> > > +
> > > +void ramblock_recv_map_init(void);
> > > +int ramblock_recv_bitmap_test(void *host_addr, RAMBlock *rb);
> > > +void ramblock_recv_bitmap_set(void *host_addr, RAMBlock *rb);
> > > +void ramblock_recv_bitmap_clear(void *host_addr, RAMBlock *rb);
> > > +
> > > #endif
> > > --
> > > 1.8.3.1
> > >
> > --
> > Dr. David Alan Gilbert / address@hidden / Manchester, UK
> >
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
Message not available