Messages in this thread | | | From | Andreas Dilger <> | Subject | Re: [PATCH v4 0/3] ext4: increase mbcache scalability | Date | Fri, 24 Jan 2014 23:09:24 -0700 |
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I think the ext4 block groups are locked with the blockgroup_lock that has about the same number of locks as the number of cores, with a max of 128, IIRC. See blockgroup_lock.h.
While there is some chance of contention, it is also unlikely that all of the cores are locking this area at the same time.
Cheers, Andreas
> On Jan 24, 2014, at 14:38, Andi Kleen <andi@firstfloor.org> wrote: > > T Makphaibulchoke <tmac@hp.com> writes: > >> The patch consists of three parts. >> >> The first part changes the implementation of both the block and hash chains of >> an mb_cache from list_head to hlist_bl_head and also introduces new members, >> including a spinlock to mb_cache_entry, as required by the second part. > > spinlock per entry is usually overkill for larger hash tables. > > Can you use a second smaller lock table that just has locks and is > indexed by a subset of the hash key. Most likely a very small > table is good enough. > > Also I would be good to have some data on the additional memory consumption. > > -Andi > > -- > ak@linux.intel.com -- Speaking for myself only
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