Messages in this thread | | | Date | Wed, 20 Mar 2002 08:54:31 +0100 | From | Jens Axboe <> | Subject | Re: 2.4.19pre3aa2 |
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On Wed, Mar 20 2002, Jari Ruusu wrote: > Jens Axboe wrote: > > On Fri, Mar 15 2002, Jari Ruusu wrote: > > > If there is any chance of being merged to mainline kernel, I will fix these > > > "hurt the eyes" formatting issues. > > > > I think there is. At least I can safely say there's no chance it will be > > merged if these things aren't fixed. So take your pick :-) > > OK, I have fixed above mentioned formatting issues. A patch is attached.
Super!
> And, about sleeping in loop_make_request(), I have also changed the code in > such way that it defaults to code that may sleep in loop_make_request(). But > non-sleeping code is still present (but not currently used), like this: > > #if 1 > may-sleep-in-loop_make_request-code-here > #else > non-sleeping-loop_make_request-code-here > #endif
The solution I prefer is to have loop_make_request() block when we run out of pre-allocated buffers, ie similar to "normal" block drivers when they run out of request slots. This provides a nice throttling mechanism and makes sure that loop doesn't eat into the memory polls too heavily.
In any way, do it one way and remove the other.
> > > > BTW, it looks like you are killing LO_FLAGS_BH_REMAP?! Why? This is a > > > > very worthwhile optimization. > > > > > > Removing it simplified the code a lot. Doing remap direcly from > > > loop_make_request() would probably be more effective. Just remap and return > > > > LOTS more effective. Please don't kill this functionality. I don't buy > > the simplification argument. > > This new patch does not remove LO_FLAGS_BH_REMAP optimization.
Good.
> > > 1 from loop_make_request() like LVM code does. > > > > And like loop currently does... > > 2.4.19-pre3 loop code wanders to loop_get_buffer() and transfer function in > LO_FLAGS_BH_REMAP optimization case. > > My version is simpler than yours: > > if (lo->lo_flags & LO_FLAGS_BH_REMAP) { > rbh->b_rsector += (lo->lo_offset >> 9); > rbh->b_rdev = lo->lo_device; > return 1; > }
So the 'new' version does exactly the same, but doesn't do it in loop_get_buffer().
-- Jens Axboe
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