On 15.10.2015 16:09, Philip Martin wrote: > There is a performance regression for checkout on NFS with 1.9. I'm > using 1.7.x as my dataset, a 95MB checkout, with localhost as my > Subversion server, so NFS is almost the only network traffic. I'm > comparing 1.7 patched to enable exclusive locking, with 1.8 and 1.9 both > with exclusive locking enabled: > > 1.7: 73s > 1.8: 66s > 1.9: 90s > > For comparison a local checkout is less than 2s. I've tried both > http:// and svn:// and get similar results. > > So 1.8 is better than patched 1.7 but 1.9 is much slower than both. > > Using "strace -c" I can see 1.9 generally makes slightly fewer system > calls apart from chmod() and ftruncate(). The extra chmod() calls are a > result of a new feature in 1.9: the pristine text-bases are read-only. > The ftruncate() calls are due to r1659426: > > Use journal_mode = TRUNCATE for sqlite [1] instead of default DELETE value. > It makes svn checkout about 10% faster on Windows at expense of one empty > file in .svn. Create/delete file is relatively expensive operation on > Windows, especially if indexes/virus scanners are enabled. > > These two changes explain the 1.9 regression, if I patch them back then > 1.9 is as good as, or better than, 1.8. > > We can't fix the chmod() problem: the new feature has a cost. We also > don't want to give up a 10% Windows gain. The TRUNCATE change is the > one that has the biggest effect on NFS performance so I propose to > continue with TRUNCATE as default but have exclusive locking mode switch > back to DELETE: > > Index: ../src-1.9/subversion/libsvn_wc/wc-queries.sql > =================================================================== > --- ../src-1.9/subversion/libsvn_wc/wc-queries.sql (revision 1708752) > +++ ../src-1.9/subversion/libsvn_wc/wc-queries.sql (working copy) > @@ -1286,7 +1286,8 @@ > OR (wc_id = ?1 AND IS_STRICT_DESCENDANT_OF(local_relpath, ?2)) > > -- STMT_PRAGMA_LOCKING_MODE > -PRAGMA locking_mode = exclusive > +PRAGMA locking_mode = exclusive; > +PRAGMA journal_mode = DELETE > > /* ------------------------------------------------------------------------- > */ > > This change brings the 1.9 checkout time down to 69s, so only 5% slower > than 1.8 rather than 36%.
And in another thread (on IRC, I think) we talked about not recommending NFS because it's not reliable given our requirement for atomic renames. -- Brane
