From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47456) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a0nu1-0007t2-DJ for qemu-devel@nongnu.org; Mon, 23 Nov 2015 04:59:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a0ntx-000698-5M for qemu-devel@nongnu.org; Mon, 23 Nov 2015 04:59:14 -0500 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> <20151123095506.GC689@ad.usersys.redhat.com> From: Wen Congyang Message-ID: <5652E33D.1070608@cn.fujitsu.com> Date: Mon, 23 Nov 2015 17:58:21 +0800 MIME-Version: 1.0 In-Reply-To: <20151123095506.GC689@ad.usersys.redhat.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit 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: Fam Zheng 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 11/23/2015 05:55 PM, Fam Zheng wrote: > 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. I don't test it. It is just a suggestion. Thanks Wen Congyang > > Fam > . >