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Re: [Qemu-devel] [PATCH] add migration capability to bypass the shared m
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH] add migration capability to bypass the shared memory |
Date: |
Wed, 10 Aug 2016 11:03:14 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) |
Lai Jiangshan <address@hidden> wrote:
Hi
First of all, I like a lot the patchset, but I would preffer to split it
to find "possible" bugs along the lines, especially in postcopy, but not only.
[very nice description of the patch]
Nothing to say about the QMP and shared memory detection, looks correct
to me.
> diff --git a/migration/ram.c b/migration/ram.c
> index 815bc0e..880972d 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -605,6 +605,28 @@ static void migration_bitmap_sync_init(void)
> num_dirty_pages_period = 0;
> xbzrle_cache_miss_prev = 0;
> iterations_prev = 0;
> + migration_dirty_pages = 0;
> +}
> +
> +static void migration_bitmap_init(unsigned long *bitmap)
> +{
> + RAMBlock *block;
> +
> + bitmap_clear(bitmap, 0, last_ram_offset() >> TARGET_PAGE_BITS);
> + rcu_read_lock();
> + QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> + if (!migrate_bypass_shared_memory() || !qemu_ram_is_shared(block)) {
> + bitmap_set(bitmap, block->offset >> TARGET_PAGE_BITS,
> + block->used_length >> TARGET_PAGE_BITS);
> +
> + /*
> + * Count the total number of pages used by ram blocks not
> including
> + * any gaps due to alignment or unplugs.
> + */
> + migration_dirty_pages += block->used_length >> TARGET_PAGE_BITS;
> + }
> + }
> + rcu_read_unlock();
> }
We can split this function in a different patch. I haven't fully search
if we care about taking the rcu lock here. The thing that I am more
interested is in knowing what happens when we don't set
migration_dirty_pages as the full "possible" memory pages.
Once here, should we check for ROM regions?
BTW, could'nt we use:
int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque)
{
RAMBlock *block;
int ret = 0;
rcu_read_lock();
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
ret = func(block->idstr, block->host, block->offset,
block->used_length, opaque);
if (ret) {
break;
}
}
rcu_read_unlock();
return ret;
}
>
> static void migration_bitmap_sync(void)
> @@ -631,7 +653,9 @@ static void migration_bitmap_sync(void)
> qemu_mutex_lock(&migration_bitmap_mutex);
> rcu_read_lock();
> QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> - migration_bitmap_sync_range(block->offset, block->used_length);
> + if (!migrate_bypass_shared_memory() || !qemu_ram_is_shared(block)) {
> + migration_bitmap_sync_range(block->offset, block->used_length);
> + }
> }
> rcu_read_unlock();
> qemu_mutex_unlock(&migration_bitmap_mutex);
Oops, another place where we were not using qemu_ram_foreach_block :p
> @@ -1926,19 +1950,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
> ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> migration_bitmap_rcu = g_new0(struct BitmapRcu, 1);
> migration_bitmap_rcu->bmap = bitmap_new(ram_bitmap_pages);
> - bitmap_set(migration_bitmap_rcu->bmap, 0, ram_bitmap_pages);
> + migration_bitmap_init(migration_bitmap_rcu->bmap);
>
> if (migrate_postcopy_ram()) {
> migration_bitmap_rcu->unsentmap = bitmap_new(ram_bitmap_pages);
> - bitmap_set(migration_bitmap_rcu->unsentmap, 0, ram_bitmap_pages);
> + bitmap_copy(migration_bitmap_rcu->unsentmap,
> + migration_bitmap_rcu->bmap, ram_bitmap_pages);
> }
I think that if we go this route, we should move the whole if inside the
migration_bitmap_init?
>
> - /*
> - * Count the total number of pages used by ram blocks not including any
> - * gaps due to alignment or unplugs.
> - */
> - migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;
> -
> memory_global_dirty_log_start();
> migration_bitmap_sync();
> qemu_mutex_unlock_ramlist();
As said, very happy with the patch. And it got much simpler that I
would have expected.
Thanks, Juan.
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, (continued)
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Li, Liang Z, 2016/08/09
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Lai Jiangshan, 2016/08/09
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Li, Liang Z, 2016/08/10
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Juan Quintela, 2016/08/10
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Li, Liang Z, 2016/08/11
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Lai Jiangshan, 2016/08/11
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Lai Jiangshan, 2016/08/11
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Li, Liang Z, 2016/08/12
- Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory, Lai Jiangshan, 2016/08/12
Re: [Qemu-devel] [PATCH] add migration capability to bypass the shared memory, Lai Jiangshan, 2016/08/09
Re: [Qemu-devel] [PATCH] add migration capability to bypass the shared memory,
Juan Quintela <=