From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Wei Yang <richardw.yang@linux.intel.com>
Cc: qemu-devel@nongnu.org, quintela@redhat.com
Subject: Re: [PATCH 1/6] migration/postcopy: reduce memset when it is zero page and matches_target_page_size
Date: Wed, 6 Nov 2019 18:18:19 +0000 [thread overview]
Message-ID: <20191106181819.GG2802@work-vm> (raw)
In-Reply-To: <20191018004850.9888-2-richardw.yang@linux.intel.com>
* Wei Yang (richardw.yang@linux.intel.com) wrote:
> In this case, page_buffer content would not be used.
>
> Skip this to save some time.
>
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
> migration/ram.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 99a98b2da4..7938a643d9 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -4091,7 +4091,13 @@ static int ram_load_postcopy(QEMUFile *f)
> switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
> case RAM_SAVE_FLAG_ZERO:
> ch = qemu_get_byte(f);
> - memset(page_buffer, ch, TARGET_PAGE_SIZE);
> + /*
> + * Can skip to set page_buffer when
> + * this is a zero page and (block->page_size == TARGET_PAGE_SIZE).
> + */
When it's zero we will use place_page_zero which doesn't need
to page_buffer; so yes that's OK; and you're right, the gotcha is with
mismatched page sizes where one subpage might be zero but not all of
them; so yes it's right that we need that check.
SO yes,
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> + if (ch || !matches_target_page_size) {
> + memset(page_buffer, ch, TARGET_PAGE_SIZE);
> + }
> if (ch) {
> all_zero = false;
> }
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2019-11-06 18:19 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 0:48 [PATCH 0/6] migration/postcopy: enable compress during postcopy Wei Yang
2019-10-18 0:48 ` [PATCH 1/6] migration/postcopy: reduce memset when it is zero page and matches_target_page_size Wei Yang
2019-11-06 18:18 ` Dr. David Alan Gilbert [this message]
2019-10-18 0:48 ` [PATCH 2/6] migration/postcopy: wait for decompress thread in precopy Wei Yang
2019-11-06 19:57 ` Dr. David Alan Gilbert
2019-10-18 0:48 ` [PATCH 3/6] migration/postcopy: count target page number to decide the place_needed Wei Yang
2019-11-06 19:59 ` Dr. David Alan Gilbert
2019-10-18 0:48 ` [PATCH 4/6] migration/postcopy: set all_zero to true on the first target page Wei Yang
2019-11-06 20:04 ` Dr. David Alan Gilbert
2019-10-18 0:48 ` [PATCH 5/6] migration/postcopy: enable random order target page arrival Wei Yang
2019-11-06 20:08 ` Dr. David Alan Gilbert
2019-11-07 6:00 ` Wei Yang
2019-11-07 9:14 ` Dr. David Alan Gilbert
2019-10-18 0:48 ` [PATCH 6/6] migration/postcopy: enable compress during postcopy Wei Yang
2019-11-06 19:55 ` Dr. David Alan Gilbert
2019-10-18 16:50 ` [PATCH 0/6] " no-reply
2019-10-19 0:15 ` Wei Yang
2019-11-06 20:11 ` Dr. David Alan Gilbert
2019-11-07 6:02 ` Wei Yang
2019-11-07 9:15 ` Dr. David Alan Gilbert
2019-11-07 12:03 ` Wei Yang
2019-11-07 12:06 ` Dr. David Alan Gilbert
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