Ryan Ding
2015-Oct-12 06:34 UTC
[Ocfs2-devel] [PATCH 0/8] ocfs2: fix ocfs2 direct io code patch to support sparse file and data ordering semantics
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(-) >>>> >>>> . >>>> >> >> . >> >
Joseph Qi
2015-Dec-10 07:54 UTC
[Ocfs2-devel] [PATCH 0/8] ocfs2: fix ocfs2 direct io code patch to support sparse file and data ordering semantics
Hi Ryan, On 2015/10/12 14:34, Ryan Ding wrote:> 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".I think we cannot mix zero pages with direct io here, which will lead to direct io data to be overwritten by zero pages. For example, a ocfs2 volume with block size 4K and cluster size 4K. Firstly I create a file with size of 5K and it will be allocated 2 clusters (8K) and the last 3K without zeroed (no need at this time). Then I seek to offset 9K and do direct write 1K, then back to 4K and do direct write 5K. Here we have to zero allocated space to avoid dirty data. But since direct write data goes to disk directly and zero pages depends on journal commit, so direct write data will be overwritten and file corrupts.>> 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(-) >>>>> >>>>> . >>>>> >>> >>> . >>> >> > > > . >