Messages in this thread | | | Date | Wed, 2 Mar 2005 09:46:37 -0800 (PST) | From | Muthian Sivathanu <> | Subject | Re: ext3 journal commit performance |
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> > > > I have a question on ext3 journal commit code. > When a > > transaction is committed in the ordered mode, ext3 > > first issues the data writes, waits for them to > > finish, then issues the journal writes, waits for > them > > to finish, and then writes out the commit record. > > > > It appears that the first wait (for the data > blocks) > > is unnecessary because all that is required is > that > > Wrong. If you perform two buffered writes > back-to-back > will you guarantee that they are both on the disk > when > the second finishes? Not on your life! They can > (read will) > be reordered depending upon the closest seek. So it > is > mandatory that one wait to make sure that both > writes > occur in order. > >
Sorry if I was unclear. I did not say that waiting for the metadata will guarantee commit of the data as well. My point is you can wait for both of them _together_ after issuing both of them to disk, instead of serializing them at the issue stage itself.
Muthian
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