Messages in this thread | | | Date | Wed, 6 Jun 2012 12:15:44 -0400 | From | Vivek Goyal <> | Subject | Re: write-behind on streaming writes |
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On Wed, Jun 06, 2012 at 08:14:08AM -0400, Vivek Goyal wrote:
[..] > I think it is happening because sync_file_range() will send all > the writes as SYNC and it will compete with firefox IO. On the other > hand, flusher's IO will show up as ASYNC and CFQ will be penalize it > heavily and firefox's IO will be prioritized. And this effect should > just get worse as more processes do sync_file_range().
Ok, this time I tried the same test again but with 4 processes doing writes in parallel on 4 different files.
And with sync_file_range() things turned ugly. Interactivity was very poor.
firefox launch test took around 1m:45s with sync_file range() while it took only about 35seconds with regular flusher threads.
So sending writeback IO synchronously wreaks havoc.
Thanks Vivek
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