Messages in this thread | | | Date | Thu, 17 Sep 2015 08:39:55 +0800 | From | He YunLei <> | Subject | Re: [f2fs-dev] [PATCH 5/7] f2fs: enhance multithread dio write performance |
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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
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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