Messages in this thread | | | Date | Tue, 24 Mar 2009 13:52:49 +0000 | From | Alan Cox <> | Subject | Re: Linux 2.6.29 |
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> They don't solve the problem where there is a *huge* amount of writes > going on, though --- if something is dirtying pages at a rate far
At very high rates other things seem to go pear shaped. I've not traced it back far enough to be sure but what I suspect occurs from the I/O at disk level is that two people are writing stuff out at once - presumably the vm paging pressure and the file system - as I see two streams of I/O that are each reasonably ordered but are interleaved.
> don't get *that* bad, even with ext3. At least, I haven't found a > workload that doesn't involve either dd if=/dev/zero or a massive > amount of data coming in over the network that will cause fsync() > delays in the > 1-2 second category. Ext3 has been around for a long
I see it with a desktop when it pages hard and also when doing heavy desktop I/O (in my case the repeatable every time case is saving large images in the gimp - A4 at 600-1200dpi).
The other one (#8636) seems to be a bug in the I/O schedulers as it goes away if you use a different I/O sched.
> solve. Simply mounting an ext3 filesystem using ext4, without making > any change to the filesystem format, should solve the problem.
I will try this experiment but not with production data just yet 8)
> some other users' data files. This was the reason for Stephen Tweedie > implementing the data=ordered mode, and making it the default.
Yes and in the server environment or for typical enterprise customers this is a *big issue*, especially the risk of it being undetected that they just inadvertently did something like put your medical data into the end of something public during a crash.
> Try ext4, I think you'll like it. :-)
I need to, so that I can double check none of the open jbd locking bugs are there and close more bugzilla entries (#8147)
Thanks for the reply - I hadn't realised a lot of this was getting fixed but in ext4 and quietly
Alan
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