On Sat, Sep 26, 2015 at 05:22:18AM +0200, Marc Lehmann wrote: > On Fri, Sep 25, 2015 at 05:47:12PM +0800, Chao Yu <chao2...@samsung.com> > wrote: > > Please revert the commit 7c5e466755ff ("f2fs: readahead cp payload > > pages when mount") since in this commit we try to access invalid > > SIT_I(sbi)->sit_base_addr which should be inited later. > > Wow, you are fast. To make it short, the new module loads and mounts. Since > systemd failed to clear the dmcache again, I need to wait a few hours for it > to write back before testing. On the plus side, this gives a fairly high > chance of fragmented memory, so I can test the code that avoids oom on mount > as well :) > > > > Since whatever speed difference I saw with two logs wasn't big, you > > > completely sold me on 6 logs, or 4 (especially if it seepds up the gc, > > > which I haven't much tested yet). Two logs was merely a test anyway (the > > > same with no_heap, I don't know what it does, but I thought it is worth > > > a try, as metadata + data nearer together is better than having them at > > > opposite ends of the log or so). > > > > If the section size is pretty large, no_heap would be enough. The original > > intention was to provide more contiguous space for data only so that a big > > file could have a large extent instead of splitting by its metadata. > > Great, so no_heap it is. > > Also, I was thinking a bit more on the active_logs issue. > > The problem with SMR drives and too many logs is not just locality, > but the fatc that appending data, unlike as with flash, requires a > read-modify-write cycle. Likewise, I am pretty sure the disk can't keep > 6 open write fragments in memory - maybe it can only keep one, so every > metadata write might cause a RMW cycle again, because it's not big enough > to fill a full zone (17-30MB). > > So, hmm, well, separating the metadata that frequently changes > (directories) form the rest is necessary for the GC to not have to copy > almost all data block, but otherwise, it's nice if everything else clumps > together. > > (likewise, stat information probably changes a lot more often than file > data, e.g. chown -R user . will change stat data regardless of whether the > files already belong to a user, and it would be nice if that menas the > data blocks can be kept untouched. Similar, renames). > > What would you recommend for this case?
Hmm, from the device side, IMO, it's not a big concern for the number of open zones, since f2fs normally tries to merge data and node IOs separately in order to submit a big IO at once. So, in my sense, it is not a big deal to use more logs. > > -- > The choice of a Deliantra, the free code+content MORPG > -----==- _GNU_ http://www.deliantra.net > ----==-- _ generation > ---==---(_)__ __ ____ __ Marc Lehmann > --==---/ / _ \/ // /\ \/ / schm...@schmorp.de > -=====/_/_//_/\_,_/ /_/\_\ > > ------------------------------------------------------------------------------ > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel ------------------------------------------------------------------------------ _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel