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Re: [Qemu-devel] [PATCH] migration/postcopy: use static PostcopyDiscardS
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] migration/postcopy: use static PostcopyDiscardState instead of allocating it for each block |
Date: |
Tue, 23 Jul 2019 16:42:12 +0100 |
User-agent: |
Mutt/1.12.0 (2019-05-25) |
* Wei Yang (address@hidden) wrote:
> On Fri, Jul 19, 2019 at 06:41:28PM +0100, Dr. David Alan Gilbert wrote:
> >* Wei Yang (address@hidden) wrote:
> >> Even we need to do discard for each RAMBlock, we still can leverage the
> >> same memory space to store the information.
> >>
> >> By doing so, we avoid memory allocation and deallocation to the system
> >> and also avoid potential failure of memory allocation which breaks the
> >> migration.
> >>
> >> Signed-off-by: Wei Yang <address@hidden>
> >> ---
> >> migration/postcopy-ram.c | 16 +++++++---------
> >> 1 file changed, 7 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> >> index 9faacacc9e..2e6b076bb7 100644
> >> --- a/migration/postcopy-ram.c
> >> +++ b/migration/postcopy-ram.c
> >> @@ -1377,8 +1377,7 @@ void
> >> postcopy_fault_thread_notify(MigrationIncomingState *mis)
> >> * asking to discard individual ranges.
> >> *
> >> * @ms: The current migration state.
> >> - * @offset: the bitmap offset of the named RAMBlock in the migration
> >> - * bitmap.
> >> + * @offset: the bitmap offset of the named RAMBlock in the migration
> >> bitmap.
> >> * @name: RAMBlock that discards will operate on.
> >> *
> >> * returns: a new PDS.
> >> @@ -1386,13 +1385,14 @@ void
> >> postcopy_fault_thread_notify(MigrationIncomingState *mis)
> >> PostcopyDiscardState *postcopy_discard_send_init(MigrationState *ms,
> >> const char *name)
> >> {
> >> - PostcopyDiscardState *res = g_malloc0(sizeof(PostcopyDiscardState));
> >> + static PostcopyDiscardState res = {0};
> >
> >Do you think it would be better to make this a static at the top of
> >migration/postcopy-ram.c and then we could remove the pds parameters
> >from postcopy_discard_send_range and friends?
>
> Just took a look into this one. One problem is not all its friends are in
> migration/postcopy-ram.c
>
> For example, postcopy_chunk_hostpages_pass() is in migration/ram.c.
But doesn't that just pass teh pds back to postcopy_discard_send_range
which is in postcopy-ram ?
Dave
> Which way do you prefer?
>
> >If there's only one pds then we don't need to pass the pointer around.
> >
> >Dave
> >
> >> - if (res) {
> >> - res->ramblock_name = name;
> >> - }
> >> + res.ramblock_name = name;
> >> + res.cur_entry = 0;
> >> + res.nsentwords = 0;
> >> + res.nsentcmds = 0;
> >>
> >> - return res;
> >> + return &res;
> >> }
> >>
> >> /**
> >> @@ -1449,8 +1449,6 @@ void postcopy_discard_send_finish(MigrationState
> >> *ms, PostcopyDiscardState *pds)
> >>
> >> trace_postcopy_discard_send_finish(pds->ramblock_name,
> >> pds->nsentwords,
> >> pds->nsentcmds);
> >> -
> >> - g_free(pds);
> >> }
> >>
> >> /*
> >> --
> >> 2.17.1
> >>
> >--
> >Dr. David Alan Gilbert / address@hidden / Manchester, UK
>
> --
> Wei Yang
> Help you, Help me
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK