Message ID | 33183CC9F5247A488A2544077AF19020815D229D@SZXEMA503-MBS.china.huawei.com |
---|---|
State | New |
Headers | show |
* Gonglei (Arei) (arei.gonglei@huawei.com) wrote: > Reducing data copy can reduce cpu overheah. (Note a few typos in subject/title) > Signed-off-by: ChenLiang <chenliang88@huawei.com> > Signed-off-by: Gonglei <arei.gonglei@huawei.com> > --- > arch_init.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/arch_init.c b/arch_init.c > index 2211e0b..cc88875 100644 > --- a/arch_init.c > +++ b/arch_init.c > @@ -344,11 +344,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, > > prev_cached_page = get_cached_data(XBZRLE.cache, current_addr); > > - /* save current buffer into memory */ > - memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE); > - > /* XBZRLE encoding (if there is no overflow) */ > - encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf, > + encoded_len = xbzrle_encode_buffer(prev_cached_page, *current_data, > TARGET_PAGE_SIZE, XBZRLE.encoded_buf, > TARGET_PAGE_SIZE); Is xbzrle_encode_buffer safe if the main memory is still being changed while it is run? Even with multiple CPUs changing it? Even on CPUs with looser memory ordering semantics? > if (encoded_len == 0) { > @@ -367,7 +364,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, > > /* we need to update the data in the cache, in order to get the same data */ > if (!last_stage) { > - memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE); > + xbzrle_decode_buffer(XBZRLE.encoded_buf, encoded_len, prev_cached_page, > + TARGET_PAGE_SIZE); > } > > /* Send XBZRLE based compressed page */ > -- > 1.7.12.4 > > > Best regards, > -Gonglei > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
On 2014/2/28 18:30, Dr. David Alan Gilbert wrote: > * Gonglei (Arei) (arei.gonglei@huawei.com) wrote: >> Reducing data copy can reduce cpu overheah. > > (Note a few typos in subject/title) > >> Signed-off-by: ChenLiang <chenliang88@huawei.com> >> Signed-off-by: Gonglei <arei.gonglei@huawei.com> >> --- >> arch_init.c | 8 +++----- >> 1 file changed, 3 insertions(+), 5 deletions(-) >> >> diff --git a/arch_init.c b/arch_init.c >> index 2211e0b..cc88875 100644 >> --- a/arch_init.c >> +++ b/arch_init.c >> @@ -344,11 +344,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, >> >> prev_cached_page = get_cached_data(XBZRLE.cache, current_addr); >> >> - /* save current buffer into memory */ >> - memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE); >> - >> /* XBZRLE encoding (if there is no overflow) */ >> - encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf, >> + encoded_len = xbzrle_encode_buffer(prev_cached_page, *current_data, >> TARGET_PAGE_SIZE, XBZRLE.encoded_buf, >> TARGET_PAGE_SIZE); > > Is xbzrle_encode_buffer safe if the main memory is still being changed while > it is run? Even with multiple CPUs changing it? Even on CPUs with looser > memory ordering semantics? > It's OK. We just need to assure the pages of cache and the pages which be sent coherence. >> if (encoded_len == 0) { >> @@ -367,7 +364,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, >> >> /* we need to update the data in the cache, in order to get the same data */ >> if (!last_stage) { >> - memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE); >> + xbzrle_decode_buffer(XBZRLE.encoded_buf, encoded_len, prev_cached_page, >> + TARGET_PAGE_SIZE); >> } >> >> /* Send XBZRLE based compressed page */ >> -- >> 1.7.12.4 >> >> >> Best regards, >> -Gonglei >> >> > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK Best regards, -Gonglei
diff --git a/arch_init.c b/arch_init.c index 2211e0b..cc88875 100644 --- a/arch_init.c +++ b/arch_init.c @@ -344,11 +344,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, prev_cached_page = get_cached_data(XBZRLE.cache, current_addr); - /* save current buffer into memory */ - memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE); - /* XBZRLE encoding (if there is no overflow) */ - encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf, + encoded_len = xbzrle_encode_buffer(prev_cached_page, *current_data, TARGET_PAGE_SIZE, XBZRLE.encoded_buf, TARGET_PAGE_SIZE); if (encoded_len == 0) { @@ -367,7 +364,8 @@ static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data, /* we need to update the data in the cache, in order to get the same data */ if (!last_stage) { - memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE); + xbzrle_decode_buffer(XBZRLE.encoded_buf, encoded_len, prev_cached_page, + TARGET_PAGE_SIZE); } /* Send XBZRLE based compressed page */