| Message ID | 1601383109-110988-7-git-send-email-andrey.shinkevich@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Apply COR-filter to the block-stream permanently | expand |
29.09.2020 15:38, Andrey Shinkevich wrote: > If the flag BDRV_REQ_PREFETCH was set, pass it further to the > COR-driver to skip unneeded reading. It can be taken into account for > the COR-algorithms optimization. That check is being made during the > block stream job by the moment. > > Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> > --- > block/copy-on-read.c | 14 ++++++++++---- > block/io.c | 2 +- > 2 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/block/copy-on-read.c b/block/copy-on-read.c > index f53f7e0..5389dca 100644 > --- a/block/copy-on-read.c > +++ b/block/copy-on-read.c > @@ -145,10 +145,16 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, > } > } > > - ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, > - local_flags); > - if (ret < 0) { > - return ret; > + if ((flags & BDRV_REQ_PREFETCH) & BDRV_REQ_PREFETCH is documented to be only used with BDRV_REQ_COPY_ON_READ. But here BDRV_REQ_COPY_ON_READ appears intermediately. We should change documentation in block.h in a separate patch (and probably code in bdrv_aligned_preadv()) > + !(local_flags & BDRV_REQ_COPY_ON_READ)) { > + /* Skip non-guest reads if no copy needed */ > + } else { > + extra new-line ? > + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, > + local_flags); > + if (ret < 0) { > + return ret; > + } > } > > offset += n; > diff --git a/block/io.c b/block/io.c > index 11df188..62b75a5 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1388,7 +1388,7 @@ static int coroutine_fn jk(BdrvChild *child, > qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum); > > ret = bdrv_driver_preadv(bs, cluster_offset, pnum, > - &local_qiov, 0, 0); > + &local_qiov, 0, flags & BDRV_REQ_PREFETCH); Why? In this place we want to read. We'll write back the data a few lines below. What will we write, if underlying driver decide to do nothing because of BDRV_REQ_PREFETCH? > if (ret < 0) { > goto err; > } >
On 07.10.2020 13:06, Vladimir Sementsov-Ogievskiy wrote: > 29.09.2020 15:38, Andrey Shinkevich wrote: >> If the flag BDRV_REQ_PREFETCH was set, pass it further to the >> COR-driver to skip unneeded reading. It can be taken into account for >> the COR-algorithms optimization. That check is being made during the >> block stream job by the moment. >> >> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> >> --- >> block/copy-on-read.c | 14 ++++++++++---- >> block/io.c | 2 +- >> 2 files changed, 11 insertions(+), 5 deletions(-) >> >> diff --git a/block/copy-on-read.c b/block/copy-on-read.c >> index f53f7e0..5389dca 100644 >> --- a/block/copy-on-read.c >> +++ b/block/copy-on-read.c >> @@ -145,10 +145,16 @@ static int coroutine_fn >> cor_co_preadv_part(BlockDriverState *bs, >> } >> } >> - ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, >> qiov_offset, >> - local_flags); >> - if (ret < 0) { >> - return ret; >> + if ((flags & BDRV_REQ_PREFETCH) & > > BDRV_REQ_PREFETCH is documented to be only used with > BDRV_REQ_COPY_ON_READ. But here > BDRV_REQ_COPY_ON_READ appears intermediately. We should change > documentation in block.h > in a separate patch (and probably code in bdrv_aligned_preadv()) > OK, we will come here without the BDRV_REQ_PREFETCH flag set. To differ between guest reads and the stream job ones, we would set it here by checking for the qiov NULL pointer: diff --git a/block/copy-on-read.c b/block/copy-on-read.c index 4e3b1c5..df2c2ab 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -144,6 +144,9 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, n, &n); if (ret) { local_flags |= BDRV_REQ_COPY_ON_READ; + if (!qiov) { + local_flags |= BDRV_REQ_PREFETCH; + } } } Andrey >> + !(local_flags & BDRV_REQ_COPY_ON_READ)) { >> + /* Skip non-guest reads if no copy needed */ >> + } else { >> + > > extra new-line ? > >> + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, >> qiov_offset, >> + local_flags); >> + if (ret < 0) { >> + return ret; >> + } >> } >> offset += n; >> diff --git a/block/io.c b/block/io.c >> index 11df188..62b75a5 100644 >> --- a/block/io.c >> +++ b/block/io.c >> @@ -1388,7 +1388,7 @@ static int coroutine_fn jk(BdrvChild *child, >> qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum); >> ret = bdrv_driver_preadv(bs, cluster_offset, pnum, >> - &local_qiov, 0, 0); >> + &local_qiov, 0, flags & >> BDRV_REQ_PREFETCH); > > Why? In this place we want to read. We'll write back the data a few > lines below. What will we write, > if underlying driver decide to do nothing because of BDRV_REQ_PREFETCH? > See my comment above please. >> if (ret < 0) { >> goto err; >> } >> > >
07.10.2020 22:01, Andrey Shinkevich wrote: > > On 07.10.2020 13:06, Vladimir Sementsov-Ogievskiy wrote: >> 29.09.2020 15:38, Andrey Shinkevich wrote: >>> If the flag BDRV_REQ_PREFETCH was set, pass it further to the >>> COR-driver to skip unneeded reading. It can be taken into account for >>> the COR-algorithms optimization. That check is being made during the >>> block stream job by the moment. >>> >>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> >>> --- >>> block/copy-on-read.c | 14 ++++++++++---- >>> block/io.c | 2 +- >>> 2 files changed, 11 insertions(+), 5 deletions(-) >>> >>> diff --git a/block/copy-on-read.c b/block/copy-on-read.c >>> index f53f7e0..5389dca 100644 >>> --- a/block/copy-on-read.c >>> +++ b/block/copy-on-read.c >>> @@ -145,10 +145,16 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, >>> } >>> } >>> - ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, >>> - local_flags); >>> - if (ret < 0) { >>> - return ret; >>> + if ((flags & BDRV_REQ_PREFETCH) & >> >> BDRV_REQ_PREFETCH is documented to be only used with BDRV_REQ_COPY_ON_READ. But here >> BDRV_REQ_COPY_ON_READ appears intermediately. We should change documentation in block.h >> in a separate patch (and probably code in bdrv_aligned_preadv()) >> > > OK, we will come here without the BDRV_REQ_PREFETCH flag set. flag BDRV_REQ_PREFETCH should be set in stream job. Where should it be handled, I don't follow? > To differ between guest reads and the stream job ones, we would set it here by checking for the qiov NULL pointer: > > > diff --git a/block/copy-on-read.c b/block/copy-on-read.c > index 4e3b1c5..df2c2ab 100644 > --- a/block/copy-on-read.c > +++ b/block/copy-on-read.c > @@ -144,6 +144,9 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, > n, &n); > if (ret) { > local_flags |= BDRV_REQ_COPY_ON_READ; > + if (!qiov) { > + local_flags |= BDRV_REQ_PREFETCH; if qiov is NULL, this means that flags must include BDRV_REQ_PREFETCH. local_flags should inherit flags I think. > + } > } > } > > Andrey > >>> + !(local_flags & BDRV_REQ_COPY_ON_READ)) { >>> + /* Skip non-guest reads if no copy needed */ >>> + } else { >>> + >> >> extra new-line ? >> >>> + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, >>> + local_flags); >>> + if (ret < 0) { >>> + return ret; >>> + } >>> } >>> offset += n; >>> diff --git a/block/io.c b/block/io.c >>> index 11df188..62b75a5 100644 >>> --- a/block/io.c >>> +++ b/block/io.c >>> @@ -1388,7 +1388,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child, >>> qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum); >>> ret = bdrv_driver_preadv(bs, cluster_offset, pnum, >>> - &local_qiov, 0, 0); >>> + &local_qiov, 0, flags & BDRV_REQ_PREFETCH); >> >> Why? In this place we want to read. We'll write back the data a few lines below. What will we write, >> if underlying driver decide to do nothing because of BDRV_REQ_PREFETCH? >> > > See my comment above please. Anyway, BDRV_REQ_PREFETCH here is wrong. You should not pass any qiov, if you set BDRV_REQ_PREFETCH flag. If we come to bdrv_co_do_copy_on_readv, it means that we have COPY_ON_READ flag. And therefore, we will handle PREFETCH and COPY_ON_READ here in generic layer. And therefore, we shouldn't pass them to driver. On the contrary, if we have PREFETCH flag in bdrv_co_aligned_preadv, but don't have COPY_ON_READ in the same time, this means that we must pass PREFETCH flag to the driver if it supports it. And do nothing if driver doesn't support PREFETCH. That's how I see it. > >>> if (ret < 0) { >>> goto err; >>> } >>> >> >>
On 07.10.2020 22:28, Vladimir Sementsov-Ogievskiy wrote: > 07.10.2020 22:01, Andrey Shinkevich wrote: >> >> On 07.10.2020 13:06, Vladimir Sementsov-Ogievskiy wrote: >>> 29.09.2020 15:38, Andrey Shinkevich wrote: >>>> If the flag BDRV_REQ_PREFETCH was set, pass it further to the >>>> COR-driver to skip unneeded reading. It can be taken into account for >>>> the COR-algorithms optimization. That check is being made during the >>>> block stream job by the moment. >>>> >>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> >>>> --- >>>> block/copy-on-read.c | 14 ++++++++++---- >>>> block/io.c | 2 +- >>>> 2 files changed, 11 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/block/copy-on-read.c b/block/copy-on-read.c >>>> index f53f7e0..5389dca 100644 >>>> --- a/block/copy-on-read.c >>>> +++ b/block/copy-on-read.c >>>> @@ -145,10 +145,16 @@ static int coroutine_fn >>>> cor_co_preadv_part(BlockDriverState *bs, >>>> } >>>> } >>>> - ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, >>>> qiov_offset, >>>> - local_flags); >>>> - if (ret < 0) { >>>> - return ret; >>>> + if ((flags & BDRV_REQ_PREFETCH) & >>> >>> BDRV_REQ_PREFETCH is documented to be only used with >>> BDRV_REQ_COPY_ON_READ. But here >>> BDRV_REQ_COPY_ON_READ appears intermediately. We should change >>> documentation in block.h >>> in a separate patch (and probably code in bdrv_aligned_preadv()) >>> >> >> OK, we will come here without the BDRV_REQ_PREFETCH flag set. > > flag BDRV_REQ_PREFETCH should be set in stream job. Where should it be > handled, I don't follow? > If we leave block/io.c unchanged in this patch, what I'm agreeing with, we'll come to the COR-driver with the hardcoded flags = 0 : #4 0x000055a22bb480cf in cor_co_preadv_part (bs=0x55a22d593710, offset=0, bytes=524288, qiov=0x0, qiov_offset=0, flags=0) at ../block/copy-on-read.c:149 #5 0x000055a22badcb1d in bdrv_driver_preadv (bs=0x55a22d593710, offset=0, bytes=524288, qiov=0x0, qiov_offset=0, flags=0) at ../block/io.c:1129 #6 0x000055a22baddc81 in bdrv_aligned_preadv (child=0x55a22d814780, req=0x7f8c1abffce0, offset=0, bytes=524288, align=1, qiov=0x0, qiov_offset=0, flags=512) at ../block/io.c:1515 #7 0x000055a22bade59a in bdrv_co_preadv_part (child=0x55a22d814780, offset=0, bytes=524288, qiov=0x0, qiov_offset=0, flags=BDRV_REQ_PREFETCH) at ../block/io.c:1757 #8 0x000055a22bade3d2 in bdrv_co_preadv (child=0x55a22d814780, offset=0, bytes=524288, qiov=0x0, flags=BDRV_REQ_PREFETCH) at ../block/io.c:1715 #9 0x000055a22baf5d09 in blk_do_preadv (blk=0x55a22d818c00, offset=0, bytes=524288, qiov=0x0, flags=BDRV_REQ_PREFETCH) at ../block/block-backend.c:1211 #10 0x000055a22baf5d61 in blk_co_preadv (blk=0x55a22d818c00, offset=0, bytes=524288, qiov=0x0, flags=BDRV_REQ_PREFETCH) at ../block/block-backend.c:1223 #11 0x000055a22bab4eba in stream_populate (blk=0x55a22d818c00, offset=0, bytes=524288) at ../block/stream.c:50 #12 0x000055a22bab52c2 in stream_run (job=0x55a22d810a20, errp=0x55a22d810aa0) at ../block/stream.c:162 #13 0x000055a22bab79f0 in job_co_entry (opaque=0x55a22d810a20) at ../job.c:908 So, the only way for the COR-filter driver to differ between guests reads and the stream job is to check the qiov pointer for NULL and reset the flags as appropriate. This is what I am going to do in the next version. Andrey >> To differ between guest reads and the stream job ones, we would set it >> here by checking for the qiov NULL pointer: >> >> >> diff --git a/block/copy-on-read.c b/block/copy-on-read.c >> index 4e3b1c5..df2c2ab 100644 >> --- a/block/copy-on-read.c >> +++ b/block/copy-on-read.c >> @@ -144,6 +144,9 @@ static int coroutine_fn >> cor_co_preadv_part(BlockDriverState *bs, >> n, &n); >> if (ret) { >> local_flags |= BDRV_REQ_COPY_ON_READ; >> + if (!qiov) { >> + local_flags |= BDRV_REQ_PREFETCH; > > if qiov is NULL, this means that flags must include BDRV_REQ_PREFETCH. > local_flags should inherit flags I think. > >> + } >> } >> } >> >> Andrey >> >>>> + !(local_flags & BDRV_REQ_COPY_ON_READ)) { >>>> + /* Skip non-guest reads if no copy needed */ >>>> + } else { >>>> + >>> >>> extra new-line ? >>> >>>> + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, >>>> qiov_offset, >>>> + local_flags); >>>> + if (ret < 0) { >>>> + return ret; >>>> + } >>>> } >>>> offset += n; >>>> diff --git a/block/io.c b/block/io.c >>>> index 11df188..62b75a5 100644 >>>> --- a/block/io.c >>>> +++ b/block/io.c >>>> @@ -1388,7 +1388,7 @@ static int coroutine_fn >>>> bdrv_co_do_copy_on_readv(BdrvChild *child, >>>> qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum); >>>> ret = bdrv_driver_preadv(bs, cluster_offset, pnum, >>>> - &local_qiov, 0, 0); >>>> + &local_qiov, 0, flags & >>>> BDRV_REQ_PREFETCH); >>> >>> Why? In this place we want to read. We'll write back the data a few >>> lines below. What will we write, >>> if underlying driver decide to do nothing because of BDRV_REQ_PREFETCH? >>> >> >> See my comment above please. > > Anyway, BDRV_REQ_PREFETCH here is wrong. You should not pass any qiov, > if you set BDRV_REQ_PREFETCH flag. > > If we come to bdrv_co_do_copy_on_readv, it means that we have > COPY_ON_READ flag. And therefore, we will handle > PREFETCH and COPY_ON_READ here in generic layer. And therefore, we > shouldn't pass them to driver. > > On the contrary, if we have PREFETCH flag in bdrv_co_aligned_preadv, but > don't have COPY_ON_READ in the same time, > this means that we must pass PREFETCH flag to the driver if it supports > it. And do nothing if driver > doesn't support PREFETCH. That's how I see it. > >> >>>> if (ret < 0) { >>>> goto err; >>>> } >>>> >>> >>> > >
diff --git a/block/copy-on-read.c b/block/copy-on-read.c index f53f7e0..5389dca 100644 --- a/block/copy-on-read.c +++ b/block/copy-on-read.c @@ -145,10 +145,16 @@ static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs, } } - ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, - local_flags); - if (ret < 0) { - return ret; + if ((flags & BDRV_REQ_PREFETCH) & + !(local_flags & BDRV_REQ_COPY_ON_READ)) { + /* Skip non-guest reads if no copy needed */ + } else { + + ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset, + local_flags); + if (ret < 0) { + return ret; + } } offset += n; diff --git a/block/io.c b/block/io.c index 11df188..62b75a5 100644 --- a/block/io.c +++ b/block/io.c @@ -1388,7 +1388,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child, qemu_iovec_init_buf(&local_qiov, bounce_buffer, pnum); ret = bdrv_driver_preadv(bs, cluster_offset, pnum, - &local_qiov, 0, 0); + &local_qiov, 0, flags & BDRV_REQ_PREFETCH); if (ret < 0) { goto err; }
If the flag BDRV_REQ_PREFETCH was set, pass it further to the COR-driver to skip unneeded reading. It can be taken into account for the COR-algorithms optimization. That check is being made during the block stream job by the moment. Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com> --- block/copy-on-read.c | 14 ++++++++++---- block/io.c | 2 +- 2 files changed, 11 insertions(+), 5 deletions(-)