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From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 15/17] block: introduce dirty_bitmap_mutex
Date: Thu, 4 May 2017 11:57:15 +0200	[thread overview]
Message-ID: <2edc4902-8698-369d-ec36-2e15c8186619@redhat.com> (raw)
In-Reply-To: <20170504075536.GB4725@lemon.lan>



On 04/05/2017 09:55, Fam Zheng wrote:
> On Thu, 04/20 14:00, Paolo Bonzini wrote:
>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
>> index 519737c..e13718e 100644
>> --- a/block/dirty-bitmap.c
>> +++ b/block/dirty-bitmap.c
>> @@ -52,6 +52,24 @@ struct BdrvDirtyBitmapIter {
>>      BdrvDirtyBitmap *bitmap;
>>  };
>>  
>> +static QemuMutex dirty_bitmap_mutex;
>> +
>> +static void __attribute__((__constructor__)) bdrv_dirty_bitmaps_init_lock(void)
>> +{
>> +    qemu_mutex_init(&dirty_bitmap_mutex);
>> +}
>> +
>> +static inline void bdrv_dirty_bitmaps_lock(BlockDriverState *bs)
>> +{
>> +    qemu_mutex_lock(&dirty_bitmap_mutex);
>> +}
>> +
>> +static inline void bdrv_dirty_bitmaps_unlock(BlockDriverState *bs)
>> +{
>> +    qemu_mutex_unlock(&dirty_bitmap_mutex);
>> +}
> 
> Why a global lock instead of a per-BDS one? The contention can be heavy if a
> block job is made to run on a different thread than the one processing guest
> I/O.

Yes, I'll introduce bs->dirty_bitmap_mutex in this patch already.

>> @@ -508,12 +550,19 @@ void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
>>                      int64_t nr_sectors)
>>  {
>>      BdrvDirtyBitmap *bitmap;
>> +
>> +    if (QLIST_EMPTY(&bs->dirty_bitmaps)) {
>> +        return;
>> +    }
> 
> Should this check be protected by lock/unlock? Or simply removed?

The check avoids taking the lock in the common case of having no dirty
bitmap.

Paolo

>> +
>> +    bdrv_dirty_bitmaps_lock(bs);
>>      QLIST_FOREACH(bitmap, &bs->dirty_bitmaps, list) {
>>          if (!bdrv_dirty_bitmap_enabled(bitmap)) {
>>              continue;
>>          }
>>          hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
>>      }
>> +    bdrv_dirty_bitmaps_unlock(bs);
>>  }
>>  
>>  /**
> 
> Fam
> 
> 

  reply	other threads:[~2017-05-04  9:57 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-20 12:00 [Qemu-devel] [PATCH for 2.10 00/17] Block layer thread safety, part 1 Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 01/17] block: access copy_on_read with atomic ops Paolo Bonzini
2017-05-04 11:15   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-05-04 11:51     ` Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 02/17] block: access quiesce_counter " Paolo Bonzini
2017-05-04 12:33   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 03/17] block: access io_limits_disabled " Paolo Bonzini
2017-05-04 12:38   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 04/17] block: access serialising_in_flight " Paolo Bonzini
2017-05-04 12:39   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 05/17] block: access wakeup " Paolo Bonzini
2017-05-04  6:39   ` Fam Zheng
2017-05-04  7:12     ` Paolo Bonzini
2017-05-04 12:47   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 06/17] block: access io_plugged " Paolo Bonzini
2017-05-04 12:48   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 07/17] throttle-groups: do not use qemu_co_enter_next Paolo Bonzini
2017-05-04 13:27   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 08/17] throttle-groups: protect throttled requests with a CoMutex Paolo Bonzini
2017-05-04  6:57   ` Fam Zheng
2017-05-04 13:56     ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 09/17] util: add stats64 module Paolo Bonzini
2017-05-04  7:19   ` Fam Zheng
2017-05-04  7:24     ` Paolo Bonzini
2017-05-04  7:36   ` Fam Zheng
2017-05-04  7:38     ` Paolo Bonzini
2017-05-04  8:55   ` [Qemu-devel] [Qemu-block] " Roman Kagan
2017-05-04  9:46     ` Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 10/17] block: use Stat64 for wr_highest_offset Paolo Bonzini
2017-05-04 14:02   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 11/17] block: access write_gen with atomics Paolo Bonzini
2017-05-04 14:04   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 12/17] block: protect tracked_requests and flush_queue with reqs_lock Paolo Bonzini
2017-05-04  7:30   ` Fam Zheng
2017-05-04  8:35     ` Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 13/17] coroutine-lock: introduce qemu_co_mutex_lock_unlock Paolo Bonzini
2017-05-04  7:39   ` Fam Zheng
2017-05-04  9:47     ` Paolo Bonzini
2017-05-04  9:52       ` Paolo Bonzini
2017-05-04 14:12   ` Stefan Hajnoczi
2017-05-04 16:17     ` Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 14/17] block: optimize access to reqs_lock Paolo Bonzini
2017-05-04 14:59   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-05-04 16:06     ` Paolo Bonzini
2017-05-05 10:25       ` Stefan Hajnoczi
2017-05-05 10:45         ` Paolo Bonzini
2017-05-08 16:21           ` Stefan Hajnoczi
2017-05-08 16:30             ` Paolo Bonzini
2017-04-20 12:00 ` [Qemu-devel] [PATCH 15/17] block: introduce dirty_bitmap_mutex Paolo Bonzini
2017-05-04  7:55   ` Fam Zheng
2017-05-04  9:57     ` Paolo Bonzini [this message]
2017-04-20 12:00 ` [Qemu-devel] [PATCH 16/17] block: protect modification of dirty bitmaps with a mutex Paolo Bonzini
2017-04-20 14:42   ` Eric Blake
2017-05-04  8:05   ` Fam Zheng
2017-05-04 10:05     ` Paolo Bonzini
2017-05-05 10:36   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-05-05 10:47     ` Paolo Bonzini
2017-05-08 16:17       ` Stefan Hajnoczi
2017-04-20 12:00 ` [Qemu-devel] [PATCH 17/17] block: make accounting thread-safe Paolo Bonzini
2017-05-05 12:56   ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-04-20 12:40 ` [Qemu-devel] [PATCH for 2.10 00/17] Block layer thread safety, part 1 no-reply
2017-04-20 12:42 ` no-reply
2017-05-02 15:42 ` Paolo Bonzini
2017-05-04  8:09 ` Fam Zheng
2017-05-05 13:01 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi

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