Messages in this thread | | | Date | Mon, 27 Oct 2008 11:42:50 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [tbench regression fixes]: digging out smelly deadmen. |
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On Sun, 26 Oct 2008, Jiri Kosina wrote:
> > > > > 208.4 MB/sec -- vanilla 2.6.16.60 > > > > > 201.6 MB/sec -- vanilla 2.6.20.1 > > > > > 172.9 MB/sec -- vanilla 2.6.22.19 > > > > > 74.2 MB/sec -- vanilla 2.6.23 > > > > > 46.1 MB/sec -- vanilla 2.6.24.2 > > > > > 30.6 MB/sec -- vanilla 2.6.26.1 > > > > > I.e. huge drop for 2.6.23 (this was with default configs for each > > > > > respective kernel). > > Was this when we decreased the default value of > > /proc/sys/vm/dirty_ratio, perhaps? dbench is sensitive to that. > 2.6.28 gives 41.8 MB/s with /proc/sys/vm/dirty_ratio == 50. So small > improvement, but still far far away from the throughput of pre-2.6.23 > kernels.
Ok, so another important datapoint:
with c1e4fe711a4 (just before CFS has been merged for 2.6.23), the dbench throughput measures
187.7 MB/s
in our testing conditions (default config).
With c31f2e8a42c4 (just after CFS has been merged for 2.6.23), the throughput measured by dbench is
82.3 MB/s
This is the huge drop we have been looking for. After this, the performance was still going down gradually, up to ~45 MS/ we are measuring for 2.6.27. But the biggest drop (more than 50%) points directly to CFS merge.
-- Jiri Kosina SUSE Labs
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