Hi, Tejun A little bit more context about this change. At Google we actively use block crgoups and generate a lot of statistics files. We have a lot of block devices per machine and usually apps in a cgroup use only small subset of the drives. While migrating to the latest kernel we've found that those stat files became much bigger - now they are full of devices with zero stats. The previous behavior seems better to me as it emphasizes device usage. I do not know whether the change was made intentionally or accidentally during block cgroups refactoring. If latter then the patch above restores the previous behavior. On Wed, Jun 26, 2013 at 12:26 PM, Anatol Pomozov <anatol.pomozov@xxxxxxxxx> wrote: > > Before 3.5 cgrups stats files shown only devices with activity. > But latest kernel shows stats for all devices. The previous implementation > looks better. Imagine a server machine with hundreds cgroups and hundreds > iSCSI block devices (where cgroup uses just a few block devices). This > generates *a lot* of useless data that requires more resources to > process/store. > > Recover previous behaviour by skipping entries with zero stats. > > Signed-off-by: Anatol Pomozov <anatol.pomozov@xxxxxxxxx> > --- > block/blk-cgroup.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > index e8918ff..915c2b0 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -548,6 +548,9 @@ u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v) > if (!dname) > return 0; > > + if (!v) > + return 0; I am not sure about this change. It looks like previously we've shown zero values here as well. But I made "drop inactive devices" here to be consistent with the change below. Feel free to drop it if you are against it. > > + > seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v); > return v; > } > @@ -571,19 +574,23 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd, > [BLKG_RWSTAT_ASYNC] = "Async", > }; > const char *dname = blkg_dev_name(pd->blkg); > - u64 v; > + u64 total; > int i; > > if (!dname) > return 0; > > + total = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE]; > + /* skip devices with no activity */ > + if (!total) > + return 0; > + > for (i = 0; i < BLKG_RWSTAT_NR; i++) > seq_printf(sf, "%s %s %llu\n", dname, rwstr[i], > (unsigned long long)rwstat->cnt[i]); > > - v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE]; > - seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v); > - return v; > + seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)total); > + return total; > } > EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat); > > -- > 1.8.3 > -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
