* Peter Xu (pet...@redhat.com) wrote: > On Wed, Oct 12, 2022 at 01:51:07PM -0400, Peter Xu wrote: > > On Wed, Oct 12, 2022 at 05:43:53PM +0100, Dr. David Alan Gilbert wrote: > > > * Peter Xu (pet...@redhat.com) wrote: > > > > Don't take the bitmap mutex when sending pages, or when being throttled > > > > by > > > > migration_rate_limit() (which is a bit tricky to call it here in ram > > > > code, > > > > but seems still helpful). > > > > > > > > It prepares for the possibility of concurrently sending pages in >1 > > > > threads > > > > using the function ram_save_host_page() because all threads may need the > > > > bitmap_mutex to operate on bitmaps, so that either sendmsg() or any > > > > kind of > > > > qemu_sem_wait() blocking for one thread will not block the other from > > > > progressing. > > > > > > > > Signed-off-by: Peter Xu <pet...@redhat.com> > > > > > > Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > > > > > > although a comment above the reclaration of ram_save_host_pages saying > > > it can drop the lock would be veyr good. > > > > Let me add that. Thanks, > > A fixup to this patch attached to touch up the comment for > ram_save_host_page().
Yep, that's right (I don't think we have any formal annotation for locks) Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > -- > Peter Xu > From dcc3adce062df7216851890d49f7d2b1fa2e84a4 Mon Sep 17 00:00:00 2001 > From: Peter Xu <pet...@redhat.com> > Date: Thu, 13 Oct 2022 12:18:04 -0400 > Subject: [PATCH] fixup! migration: Yield bitmap_mutex properly when > sending/sleeping > Content-type: text/plain > > Signed-off-by: Peter Xu <pet...@redhat.com> > --- > migration/ram.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/migration/ram.c b/migration/ram.c > index 538667b974..b311ece48c 100644 > --- a/migration/ram.c > +++ b/migration/ram.c > @@ -2407,9 +2407,14 @@ out: > * a host page in which case the remainder of the hostpage is sent. > * Only dirty target pages are sent. Note that the host page size may > * be a huge page for this block. > + * > * The saving stops at the boundary of the used_length of the block > * if the RAMBlock isn't a multiple of the host page size. > * > + * The caller must be with ram_state.bitmap_mutex held to call this > + * function. Note that this function can temporarily release the lock, but > + * when the function is returned it'll make sure the lock is still held. > + * > * Returns the number of pages written or negative on error > * > * @rs: current RAM state > -- > 2.37.3 > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
