Messages in this thread | | | Date | Tue, 11 May 2021 14:47:23 -0700 | From | Jaegeuk Kim <> | Subject | Re: [PATCH] f2fs: set file as cold when file defragmentation |
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On 05/11, Chao Yu wrote: > On 2021/5/11 14:41, Daejun Park wrote: > > > On 2021/5/11 13:09, Jaegeuk Kim wrote: > > > > On 05/11, Chao Yu wrote: > > > > > On 2021/5/10 22:47, Jaegeuk Kim wrote: > > > > > > On 05/06, Chao Yu wrote: > > > > > > > On 2021/5/6 12:46, Jaegeuk Kim wrote: > > > > > > > > On 05/06, Chao Yu wrote: > > > > > > > > > On 2021/4/29 14:20, Daejun Park wrote: > > > > > > > > > > In file defragmentation by ioctl, all data blocks in the file are > > > > > > > > > > re-written out-of-place. File defragmentation implies user will not update > > > > > > > > > > and mostly read the file. So before the defragmentation, we set file > > > > > > > > > > temperature as cold for better block allocation. > > > > > > > > > > > > > > > > > > I don't think all fragmented files are cold, e.g. db file. > > > > > > > > > > > > > > > > I have a bit different opinion. I think one example would be users want to > > > > > > > > defragment a file, when the they want to get higher read bandwidth for > > > > > > > > > > > > > > Multimedia file was already defined as cold file now via default extension > > > > > > > list? > > > > > > > > > > > > I just gave an example. And default is default. > > > > > > > > > > > > > > > > > > > > > usually multimedia files. That's likely to be cold files. Moreover, I don't > > > > > > > > think they want to defragment db files which will be fragmented soon? > > > > > > > > > > > > > > I guess like db files have less update but more access? > > > > > > > > > > > > I think both, and we set it as hot. > > > > > > > > > > Then hot and cold bit will set to the same db file after defragmentation? > > > > > > > > Do you set cold bit to db files? I mean, generally db is not cold, but hot. > > > > > > I never set cold bit to db files, I mean if we defragment db file which > > > has less update and more access, db file may have bot hot and cold bit. > > > > > > To Daejun, may I ask that is Samsung planning to use this defragment ioctl > > > in products? what's the user scenario? > > > > It is just my idea for defragmentation, not Samsung. > > Alright, > > > I think the user will call the defrag ioctl for the files that have been updated. > > Sadly, I don't see there is any user of this defragment interface since it was > been introduced... so I really don't know the real use scenario of this interface > now. > > > > > On the other hand, I think FS should be able to support defrag file even > > when in-place update is applied. What do you think? > > bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio) > { > if (f2fs_is_pinned_file(inode)) > return true; > > /* if this is cold file, we should overwrite to avoid fragmentation */ > if (file_is_cold(inode)) > return true; > > If cold bit was set, later rewrite in defragment interface can only trigger > IPU due to above IPU policy check, so after this interface, file is still > fragmented... what's the difference compared to just setting cold bit via > setxattr? > > And if user know that he will trigger less update and more read in the file, > why not just calling setxattr("system.advise", cold_bit) to set the file as > cold before it becomes fragmented, e.g. at the time of file creation?
yea, actually user can set it whatever they want after defragment. :P
> > Thanks, > > > > > Thanks, > > Daejun > > > > > > Thanks, > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > We have separated interface (via f2fs_xattr_advise_handler, e.g. setfattr -n > > > > > > > > > "system.advise" -v value) to indicate this file is a hot/cold file, so my > > > > > > > > > suggestion is after file defragmentation, if you think this file is cold, and > > > > > > > > > use setxattr() to set it as cold. > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Daejun Park <daejun7.park@samsung.com> > > > > > > > > > > --- > > > > > > > > > > fs/f2fs/file.c | 3 +++ > > > > > > > > > > 1 file changed, 3 insertions(+) > > > > > > > > > > > > > > > > > > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > > > > > > > > > index d697c8900fa7..dcac965a05fe 100644 > > > > > > > > > > --- a/fs/f2fs/file.c > > > > > > > > > > +++ b/fs/f2fs/file.c > > > > > > > > > > @@ -2669,6 +2669,9 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi, > > > > > > > > > > map.m_len = pg_end - pg_start; > > > > > > > > > > total = 0; > > > > > > > > > > + if (!file_is_cold(inode)) > > > > > > > > > > + file_set_cold(inode); > > > > > > > > > > + > > > > > > > > > > while (map.m_lblk < pg_end) { > > > > > > > > > > pgoff_t idx; > > > > > > > > > > int cnt = 0; > > > > > > > > > > > > > > > > > > . > > > > > > > > > > > > > > . > > > > > > > > > > . > > > > > > > > > > > > . > >
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