Messages in this thread |  | | | From | Neil Brown <> | | Date | Tue, 14 Nov 2006 16:44:46 +1100 | | Subject | Re: [Devel] Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list |
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On Wednesday November 1, vvs@sw.ru wrote: > > Currently we have 3 type of functions that works with dentry_unused list: > > 1) prune_dcache(NULL) -- called from shrink_dcache_memory, frees the memory and > requires global LRU. works well in current implementation. > 2) prune_dcache(sb) -- called from shrink_dcache_parent(), frees subtree, LRU > is not need here. Current implementation uses global LRU for these purposes, it > is ineffective, and patch from Neil Brown fixes this issue. > 3) shrink_dcache_sb() -- called when we need to free the unused dentries for > given super block. Current implementation is not effective too, and per-sb LRU > would be the best solution here. On the other hand patch from Neil Brown is much > better than current implementation. > > In general I think that we should approve Neil Brown's patch. We (I and Kirill > Korotaev) are ready to acknowledge it when the following remarks fill be fixed:
> > - it seems for me list_splice() is not required inside > prune_dcache(),
Yes, the list should be empty when we finish so you are right.
> - DCACHE_REFERENCED dentries should not be removed from private list to > dentry_unused list, this flag should be ignored if the private list is used,
Agreed.
> - count argument should be ignored in this case too, we want to free all the > dentries in private list,
Agreed.
> - when we shrink the whole super block we should free per-sb anonymous dentries > too (please see Kirill Korotaev's letter) >
Yes. Unfortunately I don't think it is as easy as it sounds. I'll have a closer look.
> Then I'm going to prepare new patch that will enhance the shrink_dcache_sb() > performance: > - we can add new list head into struct superblock and use it in > shrink_dcache_sb() instead of temporal private list. We will check is it empty > in dput() and add the new unused dentries to per-sb list instead of > dentry_unused list.
I think that makes sense. It means that you end up doing less work in select_parent, because the work has already been done in dput.
How is the patch going?
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