| Message ID | 20190815125538.49570-4-bfoster@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xfs: rework near mode extent allocation | expand |
On Thu, Aug 15, 2019 at 08:55:37AM -0400, Brian Foster wrote: > The last block scan is the dominant near mode allocation algorithm > for a newer filesystem with fewer, large free extents. Add debug > mode logic to randomly fall back to lookup mode to improve > regression test coverage. How about just using an errortag since the new sysfs interface lets testcases / admins control the frequency? --D > Signed-off-by: Brian Foster <bfoster@redhat.com> > --- > fs/xfs/libxfs/xfs_alloc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > index 7753b61ba532..d550aa5597bf 100644 > --- a/fs/xfs/libxfs/xfs_alloc.c > +++ b/fs/xfs/libxfs/xfs_alloc.c > @@ -1266,6 +1266,7 @@ xfs_alloc_ag_vextent_near( > int i; > xfs_agblock_t bno; > xfs_extlen_t len; > + bool lastblock; > > /* handle unitialized agbno range so caller doesn't have to */ > if (!args->min_agbno && !args->max_agbno) > @@ -1291,7 +1292,12 @@ xfs_alloc_ag_vextent_near( > * Otherwise run the optimized lookup search algorithm from the current > * location to the end of the tree. > */ > - if (xfs_btree_islastblock(acur.cnt, 0)) { > + lastblock = xfs_btree_islastblock(acur.cnt, 0); > +#ifdef DEBUG > + if (lastblock) > + lastblock = prandom_u32() & 1; > +#endif > + if (lastblock) { > int j; > > trace_xfs_alloc_cur_lastblock(args); > -- > 2.20.1 >
On Fri, Aug 16, 2019 at 06:37:03PM -0700, Darrick J. Wong wrote: > On Thu, Aug 15, 2019 at 08:55:37AM -0400, Brian Foster wrote: > > The last block scan is the dominant near mode allocation algorithm > > for a newer filesystem with fewer, large free extents. Add debug > > mode logic to randomly fall back to lookup mode to improve > > regression test coverage. > > How about just using an errortag since the new sysfs interface lets > testcases / admins control the frequency? > We could do that, but my understanding of the equivalent logic in the current algorithm is that we want broad coverage of both near mode sub-algorithms across the entire suite of tests. Hence we randomly drop allocations into either algorithm when DEBUG mode is enabled. IIRC, we do something similar with sparse inodes (i.e., randomly allocate sparse inode chunks even when unnecessary) so the functionality isn't only covered by targeted tests. Do we have the ability to have always on error tags as such? I thought we had default frequency values for each tag, but I thought they still had to be explicitly enabled. If that's the case, I'm sure we could come up with such an on-by-default mechanism and perhaps switch over these remaining DEBUG mode hacks, but that's a follow up thing IMO.. Brian > --D > > > Signed-off-by: Brian Foster <bfoster@redhat.com> > > --- > > fs/xfs/libxfs/xfs_alloc.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > > index 7753b61ba532..d550aa5597bf 100644 > > --- a/fs/xfs/libxfs/xfs_alloc.c > > +++ b/fs/xfs/libxfs/xfs_alloc.c > > @@ -1266,6 +1266,7 @@ xfs_alloc_ag_vextent_near( > > int i; > > xfs_agblock_t bno; > > xfs_extlen_t len; > > + bool lastblock; > > > > /* handle unitialized agbno range so caller doesn't have to */ > > if (!args->min_agbno && !args->max_agbno) > > @@ -1291,7 +1292,12 @@ xfs_alloc_ag_vextent_near( > > * Otherwise run the optimized lookup search algorithm from the current > > * location to the end of the tree. > > */ > > - if (xfs_btree_islastblock(acur.cnt, 0)) { > > + lastblock = xfs_btree_islastblock(acur.cnt, 0); > > +#ifdef DEBUG > > + if (lastblock) > > + lastblock = prandom_u32() & 1; > > +#endif > > + if (lastblock) { > > int j; > > > > trace_xfs_alloc_cur_lastblock(args); > > -- > > 2.20.1 > >
diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c index 7753b61ba532..d550aa5597bf 100644 --- a/fs/xfs/libxfs/xfs_alloc.c +++ b/fs/xfs/libxfs/xfs_alloc.c @@ -1266,6 +1266,7 @@ xfs_alloc_ag_vextent_near( int i; xfs_agblock_t bno; xfs_extlen_t len; + bool lastblock; /* handle unitialized agbno range so caller doesn't have to */ if (!args->min_agbno && !args->max_agbno) @@ -1291,7 +1292,12 @@ xfs_alloc_ag_vextent_near( * Otherwise run the optimized lookup search algorithm from the current * location to the end of the tree. */ - if (xfs_btree_islastblock(acur.cnt, 0)) { + lastblock = xfs_btree_islastblock(acur.cnt, 0); +#ifdef DEBUG + if (lastblock) + lastblock = prandom_u32() & 1; +#endif + if (lastblock) { int j; trace_xfs_alloc_cur_lastblock(args);
The last block scan is the dominant near mode allocation algorithm for a newer filesystem with fewer, large free extents. Add debug mode logic to randomly fall back to lookup mode to improve regression test coverage. Signed-off-by: Brian Foster <bfoster@redhat.com> --- fs/xfs/libxfs/xfs_alloc.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)