Messages in this thread | | | From | Chao Yu <> | Subject | RE: [f2fs-dev] [PATCH 5/7] f2fs: enhance multithread dio write performance | Date | Thu, 17 Sep 2015 20:53:22 +0800 |
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Hi Yunlei,
> -----Original Message----- > From: He YunLei [mailto:heyunlei@huawei.com] > Sent: Thursday, September 17, 2015 8:40 AM > To: Chao Yu > Cc: 'Jaegeuk Kim'; linux-kernel@vger.kernel.org; linux-f2fs-devel@lists.sourceforge.net > Subject: Re: [f2fs-dev] [PATCH 5/7] f2fs: enhance multithread dio write performance > > On 2015/9/16 18:15, Chao Yu wrote: > > Hi Jaegeuk, > > > >> -----Original Message----- > >> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org] > >> Sent: Wednesday, September 16, 2015 5:21 AM > >> To: Chao Yu > >> Cc: linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org > >> Subject: Re: [PATCH 5/7] f2fs: enhance multithread dio write performance > >> > >> Hi Chao, > >> > >> On Fri, Sep 11, 2015 at 02:41:53PM +0800, Chao Yu wrote: > >>> When dio writes perform concurrently, our performace will be low because of > >>> Thread A's allocation of multi continuous blocks will be break by Thread B, > >>> there are two cases as below: > >>> - In Thread B, we may change current segment to a new segment for LFS > >>> allocation if we dio write in the beginning of the file. > >>> - In Thread B, we may allocate blocks in the middle of Thread A's > >>> allocation, which make blocks which allocated in Thread A being > >>> discontinuous. > >>> > >>> This patch adds writepages mutex lock to make block allocation in dio write > >>> atomic to avoid above issues. > >>> > >>> Test environment: > >>> ubuntu os with linux kernel 4.2+, intel i7-3770, 16g memory, > >>> 32g kingston sd card. > >>> > >>> fio --name seqw --ioengine=sync --invalidate=1 --rw=write --directory=/mnt/f2fs > >> --filesize=256m --size=16m --bs=2m --direct=1 > >>> --numjobs=10 > >>> > >>> before: > >>> WRITE: io=163840KB, aggrb=3145KB/s, minb=314KB/s, maxb=411KB/s, mint=39836msec, > >> maxt=52083msec > >>> > >>> patched: > >>> WRITE: io=163840KB, aggrb=10033KB/s, minb=1003KB/s, maxb=1124KB/s, mint=14565msec, > >> maxt=16329msec > >>> > >>> Signed-off-by: Chao Yu <chao2.yu@samsung.com> > >>> --- > >>> fs/f2fs/data.c | 13 ++++++++++--- > >>> 1 file changed, 10 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > >>> index a737ca5..a0a5849 100644 > >>> --- a/fs/f2fs/data.c > >>> +++ b/fs/f2fs/data.c > >>> @@ -1536,7 +1536,9 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter > *iter, > >>> struct file *file = iocb->ki_filp; > >>> struct address_space *mapping = file->f_mapping; > >>> struct inode *inode = mapping->host; > >>> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > >>> size_t count = iov_iter_count(iter); > >>> + int rw = iov_iter_rw(iter); > >>> int err; > >>> > >>> /* we don't need to use inline_data strictly */ > >>> @@ -1555,12 +1557,17 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter > >> *iter, > >>> > >>> trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter)); > >>> > >>> - if (iov_iter_rw(iter) == WRITE) > >>> + if (rw == WRITE) { > >>> + mutex_lock(&sbi->writepages); > >> > >> Why do we have to share sbi->writepages? > > > > The root cause of this issue is that: in f2fs, we have no suitable > > dispatcher which can do the following things as an atomic operation: > > a) allocate position(s) in flash device for current block(s); > > b) submit user data in allocated position(s) in block layer. > > > > Without the dispatcher, we will suffer performance issue in following > > scenario: > > Thread A Thread B Thread C > > allocate pos+1 > > allocate pos+2 > > allocate pos+3 > > submit pos+1 > > submit pos+3 > > submit pos+2 > > > > Our final submitting series will: pos+1, pos+3, pos+2, this makes f2fs > > running into non-LFS mode, therefore resulting in bad performance. > > > > writepages mutex lock supply us with a good solution for above issue. > > It not only make the allocating and submitting pair executing atomically, > > but also reduce the fragmentation for one file since we submit blocks > > belong to single inode as continuous as possible. > > > > So here I choose to use writepages mutex lock to fix the performance > > issue caused by both dio write vs dio write and dio write vs buffered > > write. > > > > If I'm missing something, please correct me. > > > >> > >>> __allocate_data_blocks(inode, offset, count); > >> > >> If the problem lies on the misaligned blocks, how about calling mutex_unlock > >> here? > > > > When changing to unlock here, I got regression when testing with following command: > > fio --name seqw --ioengine=sync --invalidate=1 --rw=write --directory=/mnt/f2fs > --filesize=256m --size=4m --bs=64k --direct=1 > > --numjobs=20 > > > > unlock here: > > WRITE: io=81920KB, aggrb=5802KB/s, minb=290KB/s, maxb=292KB/s, mint=14010msec, > maxt=14119msec > > unlock after dio finished: > > WRITE: io=81920KB, aggrb=6088KB/s, minb=304KB/s, maxb=1081KB/s, mint=3786msec, > maxt=13454msec > > > > So how about keep it in original place in this patch? > > Does share writepages mutex lock have an effect on cache write? Here is AndroBench result on > my phone: > > Before patch: > 1R1W 8R8W 16R16W > Sequential Write 161.31 163.85 154.67 > Random Write 9.48 17.66 18.09 > > > After patch: > 1R1W 8R8W 16R16W > Sequential Write 159.61 157.24 160.11 > Random Write 9.17 8.51 8.8
Thanks for your report, I will do the investigation.
Thanks,
> > Unit:Mb/s, File size: 64M, Buffer size: 4k > > > > > Thanks, > >> > >> Thanks, > >> > >>> + } > >>> > >>> err = blockdev_direct_IO(iocb, inode, iter, offset, get_data_block_dio); > >>> - if (err < 0 && iov_iter_rw(iter) == WRITE) > >>> - f2fs_write_failed(mapping, offset + count); > >>> + if (rw == WRITE) { > >>> + mutex_unlock(&sbi->writepages); > >>> + if (err) > >>> + f2fs_write_failed(mapping, offset + count); > >>> + } > >>> > >>> trace_f2fs_direct_IO_exit(inode, offset, count, iov_iter_rw(iter), err); > >>> > >>> -- > >>> 2.4.2 > > > > > > ------------------------------------------------------------------------------ > > Monitor Your Dynamic Infrastructure at Any Scale With Datadog! > > Get real-time metrics from all of your servers, apps and tools > > in one place. > > SourceForge users - Click here to start your Free Trial of Datadog now! > > http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 > > _______________________________________________ > > Linux-f2fs-devel mailing list > > Linux-f2fs-devel@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > > > > . > >
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