lkml.org 
[lkml]   [2007]   [Dec]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 8/9] tmpfs: radix_tree_preloading
On Tue, Dec 18, 2007 at 10:05:19PM +0000, Hugh Dickins wrote:
> Nick has observed that shmem.c still uses GFP_ATOMIC when adding to page
> cache or swap cache, without any radix tree preload: so tending to deplete
> emergency reserves of memory.
>
> GFP_ATOMIC remains appropriate in shmem_writepage's add_to_swap_cache:
> it's being called under memory pressure, so must not wait for more memory
> to become available. But shmem_unuse_inode now has a window in which it
> can and should preload with GFP_KERNEL, and say GFP_NOWAIT instead of
> GFP_ATOMIC in its add_to_page_cache.
>
> shmem_getpage is not so straightforward: its filepage/swappage integrity
> relies upon exchanging between caches under spinlock, and it would need a
> lot of restructuring to place the preloads correctly. Instead, follow
> its pattern of retrying on races: use GFP_NOWAIT instead of GFP_ATOMIC in
> add_to_page_cache, and begin each circuit of the repeat loop with a sleeping
> radix_tree_preload, followed immediately by radix_tree_preload_end - that
> won't guarantee success in the next add_to_page_cache, but doesn't need to.
>
> And we can then remove that bothersome congestion_wait: when needed,
> it'll automatically get done in the course of the radix_tree_preload.
>
> Signed-off-by: Hugh Dickins <hugh@veritas.com>

Looks good to me. Thanks for this!


\
 
 \ /
  Last update: 2007-12-19 07:53    [W:0.619 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site