Before 3.5 CFQ cgroups stats was lazy initialized - the stat object was created only if the device had any I/O in that cgroup. Around 3.5 time CFQ stat structure became part of device structure. And zero stat is created when device is initialized. Initialization can happen e.g. when we configure it via 'weight_device' file. It calls cfqg_set_weight_device() and it creates cfq_group structure. But even if device is initialized the stats is still zero. If we configure all devices in all in all cgroups it generates a lot of useless stat info that takes more resources to process and store. Imagine servers with handreds cgroups and handreds iSCSI block devices. Do not print stats for inactive devices - it restores functionality that was before 3.5 Signed-off-by: Anatol Pomozov <anatol.pomozov@xxxxxxxxx> --- block/blk-cgroup.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index e8918ff..4e07e73 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -560,6 +560,7 @@ EXPORT_SYMBOL_GPL(__blkg_prfill_u64); * @rwstat: rwstat to print * * Print @rwstat to @sf for the device assocaited with @pd. + * Devices with zero activity will not be printed. */ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd, const struct blkg_rwstat *rwstat) @@ -571,19 +572,23 @@ 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
