On Mon, Feb 29, 2016 at 12:45 AM, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Sun, 2016-02-28 at 08:29 -0800, Christoph Hellwig wrote: >> On Sun, Feb 28, 2016 at 08:26:46AM -0800, James Bottomley wrote: >> > You mean in bio_add_page() the code which currently aggregates >> > chunks within a page could build a bio vec entry up to the max >> > segment size? I think that is reasonable, especially now the bio >> > splitting code can actually split inside a bio vec entry. >> >> Yes. Kent has an old prototype that did this at: >> >> https://evilpiepirate.org/git/linux-bcache.git/log/?h=block_stuff >> >> I don't think any of that is reusable as-is, but the basic idea is >> sounds and very useful. > > The basic idea, yes, but the actual code in that tree would still have > built up bv entries that are too big. We have to thread bio_add_page() > with knowledge of the queue limits, which is somewhat hard since > they're deliberately queue agnostic. Perhaps some global minimum queue > segment size would work? IMO, we can just build contiguous segment simply into one vector because bio_add_page() in hot path, then compute segments during bio splitting from submit_bio() path by applying all kinds of queue limit just like current way. Thanks Ming > > James > -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
