| Message ID | 1363956370-23681-10-git-send-email-pl@kamp.de |
|---|---|
| State | New |
| Headers | show |
On 03/22/2013 02:46 PM, Peter Lieven wrote: > at the beginning of migration all pages are marked dirty and > in the first round a bulk migration of all pages is performed. > > currently all these pages are copied to the page cache regardless > of whether they are frequently updated or not. this doesn't make sense > since most of these pages are never transferred again. > > this patch changes the XBZRLE transfer to only be used after > the bulk stage has been completed. that means a page is added > to the page cache the second time it is transferred and XBZRLE > can benefit from the third time of transfer. > > since the page cache is likely smaller than the number of pages > it's also likely that in the second round the page is missing in the > cache due to collisions in the bulk phase. > > on the other hand a lot of unnecessary mallocs, memdups and frees > are saved. > > the following results have been taken earlier while executing > the test program from docs/xbzrle.txt. (+) with the patch and (-) > without. (thanks to Eric Blake for reformatting and comments) > > + total time: 22185 milliseconds > - total time: 22410 milliseconds > > Shaved 0.3 seconds, better than 1%! > > + downtime: 29 milliseconds > - downtime: 21 milliseconds > > Not sure why downtime seemed worse, but probably not the end of the world. > > + transferred ram: 706034 kbytes > - transferred ram: 721318 kbytes > > Fewer bytes sent - good. > > + remaining ram: 0 kbytes > - remaining ram: 0 kbytes > + total ram: 1057216 kbytes > - total ram: 1057216 kbytes > + duplicate: 108556 pages > - duplicate: 105553 pages > + normal: 175146 pages > - normal: 179589 pages > + normal bytes: 700584 kbytes > - normal bytes: 718356 kbytes > > Fewer normal bytes... > > + cache size: 67108864 bytes > - cache size: 67108864 bytes > + xbzrle transferred: 3127 kbytes > - xbzrle transferred: 630 kbytes > > ...and more compressed pages sent - good. > > + xbzrle pages: 117811 pages > - xbzrle pages: 21527 pages > + xbzrle cache miss: 18750 > - xbzrle cache miss: 179589 > > And very good improvement on the cache miss rate. > > + xbzrle overflow : 0 > - xbzrle overflow : 0 > > Signed-off-by: Peter Lieven <pl@kamp.de> > Reviewed-by: Eric Blake <eblake@redhat.com> > --- > arch_init.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch_init.c b/arch_init.c > index b2b932a..86f7e28 100644 > --- a/arch_init.c > +++ b/arch_init.c > @@ -464,7 +464,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage) > acct_info.skipped_pages++; > bytes_sent = 0; > } > - } else if (migrate_use_xbzrle()) { > + } else if (!ram_bulk_stage && migrate_use_xbzrle()) { > current_addr = block->offset + offset; > bytes_sent = save_xbzrle_page(f, p, current_addr, block, > offset, cont, last_stage); > Reviewed-by: Orit Wasserman <owasserm@redhat.com>
diff --git a/arch_init.c b/arch_init.c index b2b932a..86f7e28 100644 --- a/arch_init.c +++ b/arch_init.c @@ -464,7 +464,7 @@ static int ram_save_block(QEMUFile *f, bool last_stage) acct_info.skipped_pages++; bytes_sent = 0; } - } else if (migrate_use_xbzrle()) { + } else if (!ram_bulk_stage && migrate_use_xbzrle()) { current_addr = block->offset + offset; bytes_sent = save_xbzrle_page(f, p, current_addr, block, offset, cont, last_stage);