On 04/27/2016 01:24 AM, Chandan Rajendra wrote:
On Tuesday 26 Apr 2016 11:51:22 Josef Bacik wrote:
+int set_page_extent_mapped(struct page *page)
{
+ struct btrfs_page_private *pg_private;
+
if (!PagePrivate(page)) {
+ pg_private = kzalloc(sizeof(*pg_private), GFP_NOFS);
+ if (!pg_private)
+ return -ENOMEM;
So I would like to avoid the per-page allocation in the case that
sectorsize == pagesize. Also this is going to be pretty heavily used,
so a separate slab should be used.
Ok. I will revise this patch and other dependent patches to determine the
block states (dirty, uptodate, etc) from either page flags (for sectorsize ==
pagesize) or from the per-page bitmap (for sectorsize < pagesize).
In fact, couldn't we just use the extent io tree to deal with this? It
would be kind of heavy handed to have to look up in the io tree for
every sub page range I suppose, but we could probably avoid doing it in
most cases and only in the case that we know we're only doing the sub
page IO. Thanks,
Commit 1edbb734b4e010974c41d2859d22a43d04f5f1cf (Btrfs: reduce CPU usage in
the extent_state tree) dropped support for tracking block states using extent
io tree citing performance reasons. The initial versions of subpage-blocksize
patchset did bring back this feature. However during Btrfs BoF meetup during
2015 Vault conference, we decided to go with the per-page bitmap to track the
block states.
Lol ok carry on then. Thanks,
Josef
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