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(). -- 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
