From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46911) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a0nq7-0006b6-VJ for qemu-devel@nongnu.org; Mon, 23 Nov 2015 04:55:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a0nq6-0005Bu-WD for qemu-devel@nongnu.org; Mon, 23 Nov 2015 04:55:15 -0500 Date: Mon, 23 Nov 2015 17:55:06 +0800 From: Fam Zheng Message-ID: <20151123095506.GC689@ad.usersys.redhat.com> References: <1448013593-14282-1-git-send-email-famz@redhat.com> <1448013593-14282-2-git-send-email-famz@redhat.com> <5652D602.8010809@cn.fujitsu.com> <20151123091911.GB689@ad.usersys.redhat.com> <5652DB34.5090300@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5652DB34.5090300@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH for 2.6 1/3] backup: Use Bitmap to replace "s->bitmap" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wen Congyang Cc: Kevin Wolf , vsementsov@virtuozzo.com, qemu-block@nongnu.org, Jeff Cody , qemu-devel@nongnu.org, mreitz@redhat.com, pbonzini@redhat.com, jsnow@redhat.com On Mon, 11/23 17:24, Wen Congyang wrote: > On 11/23/2015 05:19 PM, Fam Zheng wrote: > > On Mon, 11/23 17:01, Wen Congyang wrote: > >> On 11/20/2015 05:59 PM, Fam Zheng wrote: > >>> "s->bitmap" tracks done sectors, we only check bit states without using any > >>> iterator which HBitmap is good for. Switch to "Bitmap" which is simpler and > >>> more memory efficient. > >>> > >>> Meanwhile, rename it to done_bitmap, to reflect the intention. > >>> > >>> Signed-off-by: Fam Zheng > >>> --- > >>> block/backup.c | 11 ++++++----- > >>> 1 file changed, 6 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/block/backup.c b/block/backup.c > >>> index 3b39119..d408f98 100644 > >>> --- a/block/backup.c > >>> +++ b/block/backup.c > >>> @@ -22,6 +22,7 @@ > >>> #include "qapi/qmp/qerror.h" > >>> #include "qemu/ratelimit.h" > >>> #include "sysemu/block-backend.h" > >>> +#include "qemu/bitmap.h" > >>> > >>> #define BACKUP_CLUSTER_BITS 16 > >>> #define BACKUP_CLUSTER_SIZE (1 << BACKUP_CLUSTER_BITS) > >>> @@ -47,7 +48,7 @@ typedef struct BackupBlockJob { > >>> BlockdevOnError on_target_error; > >>> CoRwlock flush_rwlock; > >>> uint64_t sectors_read; > >>> - HBitmap *bitmap; > >>> + unsigned long *done_bitmap; > >>> QLIST_HEAD(, CowRequest) inflight_reqs; > >>> } BackupBlockJob; > >>> > >>> @@ -113,7 +114,7 @@ static int coroutine_fn backup_do_cow(BlockDriverState *bs, > >>> cow_request_begin(&cow_request, job, start, end); > >>> > >>> for (; start < end; start++) { > >>> - if (hbitmap_get(job->bitmap, start)) { > >>> + if (test_bit(start, job->done_bitmap)) { > >>> trace_backup_do_cow_skip(job, start); > >>> continue; /* already copied */ > >>> } > >>> @@ -164,7 +165,7 @@ static int coroutine_fn backup_do_cow(BlockDriverState *bs, > >>> goto out; > >>> } > >>> > >>> - hbitmap_set(job->bitmap, start, 1); > >>> + bitmap_set(job->done_bitmap, start, 1); > >> > >> You can use set_bit() here. > > > > Why? I think bitmap_set is a better match with bitmap_new below. > > set_bit() is quicker than bitmap_set() if you only set one bit. > How much quicker is it? This doesn't sound convincing enough for me to lose the readability. Fam