Messages in this thread | | | Date | Thu, 25 May 2006 15:56:24 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 08/33] readahead: common macros |
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Wu Fengguang wrote:
>Define some common used macros for the read-ahead logics. > >Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> >--- > > mm/readahead.c | 14 ++++++++++++-- > 1 files changed, 12 insertions(+), 2 deletions(-) > >--- linux-2.6.17-rc4-mm3.orig/mm/readahead.c >+++ linux-2.6.17-rc4-mm3/mm/readahead.c >@@ -5,6 +5,8 @@ > * > * 09Apr2002 akpm@zip.com.au > * Initial version. >+ * 21May2006 Wu Fengguang <wfg@mail.ustc.edu.cn> >+ * Adaptive read-ahead framework. > */ > > #include <linux/kernel.h> >@@ -14,6 +16,14 @@ > #include <linux/blkdev.h> > #include <linux/backing-dev.h> > #include <linux/pagevec.h> >+#include <linux/writeback.h> >+#include <linux/nfsd/const.h> >
How come you're adding these includes?
>+ >+#define PAGES_BYTE(size) (((size) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) >+#define PAGES_KB(size) PAGES_BYTE((size)*1024) > Don't really like the names. Don't think they do anything for clarity, but if you can come up with something better for PAGES_BYTE I might change my mind ;) (just forget about PAGES_KB - people know what *1024 means)
Also: the replacements are wrong: if you've defined VM_MAX_READAHEAD to be 4095 bytes, you don't want the _actual_ readahead to be 4096 bytes, do you? It is saying nothing about minimum, so presumably 0 is the correct choice.
>+ >+#define next_page(pg) (list_entry((pg)->lru.prev, struct page, lru)) >+#define prev_page(pg) (list_entry((pg)->lru.next, struct page, lru)) >
Again, it is probably easier just to use the expanded version. Then the reader can immediately say: ah, the next page on the LRU list (rather than, maybe, the next page in the pagecache).
> > void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) > { >@@ -21,7 +31,7 @@ void default_unplug_io_fn(struct backing > EXPORT_SYMBOL(default_unplug_io_fn); > > struct backing_dev_info default_backing_dev_info = { >- .ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE, >+ .ra_pages = PAGES_KB(VM_MAX_READAHEAD), > .state = 0, > .capabilities = BDI_CAP_MAP_COPY, > .unplug_io_fn = default_unplug_io_fn, >@@ -50,7 +60,7 @@ static inline unsigned long get_max_read > > static inline unsigned long get_min_readahead(struct file_ra_state *ra) > { >- return (VM_MIN_READAHEAD * 1024) / PAGE_CACHE_SIZE; >+ return PAGES_KB(VM_MIN_READAHEAD); > } > > static inline void reset_ahead_window(struct file_ra_state *ra) > >-- >
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