From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryan Ding Date: Mon, 12 Oct 2015 14:34:28 +0800 Subject: [Ocfs2-devel] [PATCH 0/8] ocfs2: fix ocfs2 direct io code patch to support sparse file and data ordering semantics In-Reply-To: <561609A0.5010108@huawei.com> References: <1441959559-29947-1-git-send-email-ryan.ding@oracle.com> <5609148B.6040506@huawei.com> <5615DF35.3030802@oracle.com> <561609A0.5010108@huawei.com> Message-ID: <561B5474.6060104@oracle.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Hi Joseph, On 10/08/2015 02:13 PM, Joseph Qi wrote: > Hi Ryan, > > On 2015/10/8 11:12, Ryan Ding wrote: >> Hi Joseph, >> >> On 09/28/2015 06:20 PM, Joseph Qi wrote: >>> Hi Ryan, >>> I have gone through this patch set and done a simple performance test >>> using direct dd, it indeed brings much performance promotion. >>> Before After >>> bs=4K 1.4 MB/s 5.0 MB/s >>> bs=256k 40.5 MB/s 56.3 MB/s >>> >>> My questions are: >>> 1) You solution is still using orphan dir to keep inode and allocation >>> consistency, am I right? From our test, it is the most complicated part >>> and has many race cases to be taken consideration. So I wonder if this >>> can be restructured. >> I have not got a better idea to do this. I think the only reason why direct io using orphan is to prevent space lost when system crash during append direct write. But maybe a 'fsck -f' will do that job. Is it necessary to use orphan? > The idea is taken from ext4, but since ocfs2 is cluster filesystem, so > it is much more complicated than ext4. > And fsck can only be used offline, but using orphan is to perform > recovering online. So I don't think fsck can replace it in all cases. > >>> 2) Rather than using normal block direct io, you introduce a way to use >>> write begin/end in buffer io. IMO, if it wants to perform like direct >>> io, it should be committed to disk by forcing committing journal. But >>> journal committing will consume much time. Why does it bring performance >>> promotion instead? >> I use buffer io to write only the zero pages. Actual data payload is written as direct io. I think there is no need to do a force commit. Because direct means "Try to minimize cache effects of the I/O to and from this file.", it does not means "write all data & meta data to disk before write return". > So this is protected by "UNWRITTEN" flag, right? > >>> 3) Do you have a test in case of lack of memory? >> I tested it in a system with 2GB memory. Is that enough? > What I mean is doing many direct io jobs in case system free memory is > low. I understand what you mean, but did not find a better way to test it. Since if free memory is too low, even the process can not be started. If free memory is fairlyenough, the test has no meaning. So I try to collect the memory usage during io, and do a comparison test with buffer io. The result is: 1. start 100 dd to do 4KB direct write: [root at hnode3 ~]# cat /proc/meminfo | grep -E "^Cached|^Dirty|^MemFree|^MemTotal|^Buffers|^Writeback:" MemTotal: 2809788 kB MemFree: 21824 kB Buffers: 55176 kB Cached: 2513968 kB Dirty: 412 kB Writeback: 36 kB 2. start 100 dd to do 4KB buffer write: [root at hnode3 ~]# cat /proc/meminfo | grep -E "^Cached|^Dirty|^MemFree|^MemTotal|^Buffers|^Writeback:" MemTotal: 2809788 kB MemFree: 22476 kB Buffers: 15696 kB Cached: 2544892 kB Dirty: 320136 kB Writeback: 146404 kB You can see from the 'Dirty' and 'Writeback' field that there is not so much memory used as buffer io. So I think what you concern is no longer exist. :-) Thanks, Ryan > > Thanks, > Joesph > >> Thanks, >> Ryan >>> On 2015/9/11 16:19, Ryan Ding wrote: >>>> The idea is to use buffer io(more precisely use the interface >>>> ocfs2_write_begin_nolock & ocfs2_write_end_nolock) to do the zero work beyond >>>> block size. And clear UNWRITTEN flag until direct io data has been written to >>>> disk, which can prevent data corruption when system crashed during direct write. >>>> >>>> And we will also archive a better performance: >>>> eg. dd direct write new file with block size 4KB: >>>> before this patch: >>>> 2.5 MB/s >>>> after this patch: >>>> 66.4 MB/s >>>> >>>> ---------------------------------------------------------------- >>>> Ryan Ding (8): >>>> ocfs2: add ocfs2_write_type_t type to identify the caller of write >>>> ocfs2: use c_new to indicate newly allocated extents >>>> ocfs2: test target page before change it >>>> ocfs2: do not change i_size in write_end for direct io >>>> ocfs2: return the physical address in ocfs2_write_cluster >>>> ocfs2: record UNWRITTEN extents when populate write desc >>>> ocfs2: fix sparse file & data ordering issue in direct io. >>>> ocfs2: code clean up for direct io >>>> >>>> fs/ocfs2/aops.c | 1118 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------------------------------------------------------------------------------------ >>>> fs/ocfs2/aops.h | 11 +- >>>> fs/ocfs2/file.c | 138 +--------------------- >>>> fs/ocfs2/inode.c | 3 + >>>> fs/ocfs2/inode.h | 3 + >>>> fs/ocfs2/mmap.c | 4 +- >>>> fs/ocfs2/ocfs2_trace.h | 16 +-- >>>> fs/ocfs2/super.c | 1 + >>>> 8 files changed, 568 insertions(+), 726 deletions(-) >>>> >>>> . >>>> >> >> . >> >