Messages in this thread | | | Date | Fri, 22 Dec 2000 17:45:57 +0100 | From | Daniel Phillips <> | Subject | Re: [RFC] changes to buffer.c (was Test12 ll_rw_block error) |
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Chris Mason wrote: > > On Thursday, December 21, 2000 22:38:04 -0200 Marcelo Tosatti <marcelo@conectiva.com.br> wrote: > > > > On Thu, 21 Dec 2000, Andreas Dilger wrote: > > > >> Marcelo Tosatti writes: > >> > It seems your code has a problem with bh flush time. > >> > > >> > In flush_dirty_buffers(), a buffer may (if being called from kupdate) only > >> > be written in case its old enough. (bh->b_flushtime) > >> > > >> > If the flush happens for an anonymous buffer, you'll end up writing all > >> > buffers which are sitting on the same page (with block_write_anon_page), > >> > but these other buffers are not necessarily old enough to be flushed. > >> > >> This isn't really a "problem" however. The page is the _maximum_ age of > >> the buffer before it needs to be written. If we can efficiently write it > >> out with another buffer > > > >> (essentially for free if they are on the same spot on disk) > > > > Are you sure this is true for buffer pages in most cases? > > It's a good point. block_write_anon_page could be changed to just > write the oldest buffer and redirty the page (if the buffers are > far apart). If memory is tight, and we *really* need the page back, > it will be flushed by try_to_free_buffers. > > It seems a bit nasty to me though...writepage should write the page.
Um. Why cater to the uncommon case of 1K blocks? Just let bdflush/kupdated deal with them in the normal way - it's pretty efficient. Only try to do the clustering optimization when buffer size matches memory page size.
-- Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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