Re: ext4: performance regression introduced by the cgroup writeback support

[Tejun Heo]

On Wed, Sep 23, 2015 at 12:13:59PM -0400, Chris Mason wrote:
> > The issue is: under high CPU and disk I/O pressure, *some* processes can suffer from a very slow write speed (e.g., <1MB/s or even only 20KB/s), while the normal write speed should be at least dozens of MB/s.

So, I think I know what caused this regression.  Separate wb domains
shouldn't have been enabled on traditional hierarchies.  It doesn't
work there and leads to multiple wb domains competing on the same
blkcg and the bw estimation would go completely haywire.  Will update
soon.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/