[lkml]   [2008]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] splitlru: BDI_CAP_SWAP_BACKED
> The split-lru patches put file and swap-backed pages on different lrus.
> shmem/tmpfs pages are awkward because they are swap-backed file pages.
> Since it's difficult to change lru midstream, they are treated as swap-
> backed throughout, with SetPageSwapBacked on allocation in shmem_getpage.
> However, splice read (used by loop and sendfile) and readahead* allocate
> pages first, add_to_page_cache_lru, and then call into the filesystem
> through ->readpage. Under memory pressure, the shmem pages arrive at
> add_to_swap_cache and hit its BUG_ON(!PageSwapBacked(page)).
> I've not yet found a better way to handle this than a "capability"
> flag in shmem_backing_dev_info, tested by add_to_page_cache_lru.
> And solely because it would look suspicious without it, set that
> BDI_CAP_SWAP_BACKED in swap_backing_dev_info also.
> * readahead on shmem/tmpfs? I'd always thought ra_pages 0 prevented
> that; but in fact readahead(2), fadvise(POSIX_FADV_WILLNEED) and
> madvise(MADV_WILLNEED) all force_page_cache_readahead and get there.
> Signed-off-by: Hugh Dickins <>


I'm not sure about this patch is perfect.
but it seems makes sense and very good code.

So, I'll testing this patch for a while.

Rik, What do you think about it?

 \ /
  Last update: 2008-06-29 10:53    [W:0.213 / U:0.352 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site