summaryrefslogtreecommitdiffstats
Commit message (Collapse)AuthorAgeFilesLines
* fs: improve scalability of pseudo filesystemsNick Piggin2011-01-075-3/+16
| | | | | | | | | Regardless of how much we possibly try to scale dcache, there is likely always going to be some fundamental contention when adding or removing children under the same parent. Pseudo filesystems do not seem need to have connected dentries because by definition they are disconnected. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache per-inode inode alias lockingNick Piggin2011-01-079-60/+67
| | | | | | | | | dcache_inode_lock can be replaced with per-inode locking. Use existing inode->i_lock for this. This is slightly non-trivial because we sometimes need to find the inode from the dentry, which requires d_inode to be stabilised (either with refcount or d_lock). Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache per-bucket dcache hash lockingNick Piggin2011-01-074-53/+89
| | | | | | | We can turn the dcache hash locking from a global dcache_hash_lock into per-bucket locking. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* bit_spinlock: add required includesNick Piggin2011-01-071-0/+4
| | | | Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* kernel: add bl_listNick Piggin2011-01-072-0/+271
| | | | | | | | | | Introduce a type of hlist that can support the use of the lowest bit in the hlist_head. This will be subsequently used to implement per-bucket bit spinlock for inode and dentry hashes, and may be useful in other cases such as network hashes. Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* xfs: provide simple rcu-walk ACL implementationNick Piggin2011-01-071-3/+6
| | | | | | | This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* btrfs: provide simple rcu-walk ACL implementationNick Piggin2011-01-072-12/+12
| | | | | | | This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* ext2,3,4: provide simple rcu-walk ACL implementationNick Piggin2011-01-073-6/+15
| | | | | | | This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: provide simple rcu-walk generic_check_acl implementationNick Piggin2011-01-072-10/+31
| | | | | | | | | | | | | | | | | | This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. This could easily be extended to put acls under RCU and check them under seqlock, if need be. But this implementation is enough to show the rcu-walk aware permissions code for path lookups is working, and will handle cases where there are no ACLs or ACLs in just the final element. This patch implicity converts tmpfs to rcu-aware permission check. Subsequent patches onvert ext*, xfs, and, btrfs. Each of these uses acl/permission code in a different way, so convert them all to provide templates and proof of concept. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: provide rcu-walk aware permission i_opsNick Piggin2011-01-0760-146/+287
| | | | Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: rcu-walk aware d_revalidate methodNick Piggin2011-01-0727-61/+215
| | | | | | | | Require filesystems be aware of .d_revalidate being called in rcu-walk mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning -ECHILD from all implementations. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: cache optimise dentry and inode for rcu-walkNick Piggin2011-01-073-38/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | Put dentry and inode fields into top of data structure. This allows RCU path traversal to perform an RCU dentry lookup in a path walk by touching only the first 56 bytes of the dentry. We also fit in 8 bytes of inline name in the first 64 bytes, so for short names, only 64 bytes needs to be touched to perform the lookup. We should get rid of the hash->prev pointer from the first 64 bytes, and fit 16 bytes of name in there, which will take care of 81% rather than 32% of the kernel tree. inode is also rearranged so that RCU lookup will only touch a single cacheline in the inode, plus one in the i_ops structure. This is important for directory component lookups in RCU path walking. In the kernel source, directory names average is around 6 chars, so this works. When we reach the last element of the lookup, we need to lock it and take its refcount which requires another cacheline access. Align dentry and inode operations structs, so members will be at predictable offsets and we can group common operations into head of structure. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce branches in lookup pathNick Piggin2011-01-0763-137/+174
| | | | | | | | | | | | | | Reduce some branches and memory accesses in dcache lookup by adding dentry flags to indicate common d_ops are set, rather than having to check them. This saves a pointer memory access (dentry->d_op) in common path lookup situations, and saves another pointer load and branch in cases where we have d_op but not the particular operation. Patched with: git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache remove d_mountedNick Piggin2011-01-074-27/+58
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rather than keep a d_mounted count in the dentry, set a dentry flag instead. The flag can be cleared by checking the hash table to see if there are any mounts left, which is not time critical because it is performed at detach time. The mounted state of a dentry is only used to speculatively take a look in the mount hash table if it is set -- before following the mount, vfsmount lock is taken and mount re-checked without races. This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I might use later (and some configs have larger than 32-bit spinlocks which might make use of the hole). Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>: In autofs4, when expring direct (or offset) mounts we need to ensure that we block user path walks into the autofs mount, which is covered by another mount. To do this we clear the mounted status so that follows stop before walking into the mount and are essentially blocked until the expire is completed. The automount daemon still finds the correct dentry for the umount due to the follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as an inode operation for direct and offset mounts only and is called following the lookup that stopped at the covered mount. At the end of the expire the covering mount probably has gone away so the mounted status need not be restored. But we need to check this and only restore the mounted status if the expire failed. XXX: autofs may not work right if we have other mounts go over the top of it? Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: fs_struct use seqlockNick Piggin2011-01-073-13/+34
| | | | | | | | | | | | Use a seqlock in the fs_struct to enable us to take an atomic copy of the complete cwd and root paths. Use this in the RCU lookup path to avoid a thread-shared spinlock in RCU lookup operations. Multi-threaded apps may now perform path lookups with scalability matching multi-process apps. Operations such as stat(2) become very scalable for multi-threaded workload. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: rcu-walk for path lookupNick Piggin2011-01-0710-340/+1194
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Perform common cases of path lookups without any stores or locking in the ancestor dentry elements. This is called rcu-walk, as opposed to the current algorithm which is a refcount based walk, or ref-walk. This results in far fewer atomic operations on every path element, significantly improving path lookup performance. It also avoids cacheline bouncing on common dentries, significantly improving scalability. The overall design is like this: * LOOKUP_RCU is set in nd->flags, which distinguishes rcu-walk from ref-walk. * Take the RCU lock for the entire path walk, starting with the acquiring of the starting path (eg. root/cwd/fd-path). So now dentry refcounts are not required for dentry persistence. * synchronize_rcu is called when unregistering a filesystem, so we can access d_ops and i_ops during rcu-walk. * Similarly take the vfsmount lock for the entire path walk. So now mnt refcounts are not required for persistence. Also we are free to perform mount lookups, and to assume dentry mount points and mount roots are stable up and down the path. * Have a per-dentry seqlock to protect the dentry name, parent, and inode, so we can load this tuple atomically, and also check whether any of its members have changed. * Dentry lookups (based on parent, candidate string tuple) recheck the parent sequence after the child is found in case anything changed in the parent during the path walk. * inode is also RCU protected so we can load d_inode and use the inode for limited things. * i_mode, i_uid, i_gid can be tested for exec permissions during path walk. * i_op can be loaded. When we reach the destination dentry, we lock it, recheck lookup sequence, and increment its refcount and mountpoint refcount. RCU and vfsmount locks are dropped. This is termed "dropping rcu-walk". If the dentry refcount does not match, we can not drop rcu-walk gracefully at the current point in the lokup, so instead return -ECHILD (for want of a better errno). This signals the path walking code to re-do the entire lookup with a ref-walk. Aside from the final dentry, there are other situations that may be encounted where we cannot continue rcu-walk. In that case, we drop rcu-walk (ie. take a reference on the last good dentry) and continue with a ref-walk. Again, if we can drop rcu-walk gracefully, we return -ECHILD and do the whole lookup using ref-walk. But it is very important that we can continue with ref-walk for most cases, particularly to avoid the overhead of double lookups, and to gain the scalability advantages on common path elements (like cwd and root). The cases where rcu-walk cannot continue are: * NULL dentry (ie. any uncached path element) * parent with d_inode->i_op->permission or ACLs * dentries with d_revalidate * Following links In future patches, permission checks and d_revalidate become rcu-walk aware. It may be possible eventually to make following links rcu-walk aware. Uncached path elements will always require dropping to ref-walk mode, at the very least because i_mutex needs to be grabbed, and objects allocated. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* kernel: optimise seqlockNick Piggin2011-01-071-7/+73
| | | | | | | | | Add branch annotations for seqlock read fastpath, and introduce __read_seqcount_begin and __read_seqcount_end functions, that can avoid the smp_rmb() if used carefully. These will be used by store-free path walking algorithm performance is critical and seqlocks are in use. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: avoid inode RCU freeing for pseudo fsNick Piggin2011-01-075-9/+22
| | | | | | | Pseudo filesystems that don't put inode on RCU list or reachable by rcu-walk dentries do not need to RCU free their inodes. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: icache RCU free inodesNick Piggin2011-01-0760-68/+490
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | RCU free the struct inode. This will allow: - Subsequent store-free path walking patch. The inode must be consulted for permissions when walking, so an RCU inode reference is a must. - sb_inode_list_lock to be moved inside i_lock because sb list walkers who want to take i_lock no longer need to take sb_inode_list_lock to walk the list in the first place. This will simplify and optimize locking. - Could remove some nested trylock loops in dcache code - Could potentially simplify things a bit in VM land. Do not need to take the page lock to follow page->mapping. The downsides of this is the performance cost of using RCU. In a simple creat/unlink microbenchmark, performance drops by about 10% due to inability to reuse cache-hot slab objects. As iterations increase and RCU freeing starts kicking over, this increases to about 20%. In cases where inode lifetimes are longer (ie. many inodes may be allocated during the average life span of a single inode), a lot of this cache reuse is not applicable, so the regression caused by this patch is smaller. The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU, however this adds some complexity to list walking and store-free path walking, so I prefer to implement this at a later date, if it is shown to be a win in real situations. I haven't found a regression in any non-micro benchmark so I doubt it will be a problem. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: consolidate dentry kill sequenceNick Piggin2011-01-071-74/+61
| | | | | | | | The tricky locking for disposing of a dentry is duplicated 3 times in the dcache (dput, pruning a dentry from the LRU, and pruning its ancestors). Consolidate them all into a single function dentry_kill. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: use RCU in shrink_dentry_list to reduce lock nestingNick Piggin2011-01-071-21/+25
| | | | Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: reduce dcache_inode_lock width in lru scanningNick Piggin2011-01-071-8/+8
| | | | Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce prune_one_dentry lockingNick Piggin2011-01-071-12/+15
| | | | | | | | | prune_one_dentry can avoid quite a bit of locking in the common case where ancestors have an elevated refcount. Alternatively, we could have gone the other way and made fewer trylocks in the case where d_count goes to zero, but is probably less common. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce d_parent lockingNick Piggin2011-01-071-9/+12
| | | | | | Use RCU to simplify locking in dget_parent. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache rationalise dget variantsNick Piggin2011-01-0712-47/+24
| | | | | | | | | | dget_locked was a shortcut to avoid the lazy lru manipulation when we already held dcache_lock (lru manipulation was relatively cheap at that point). However, how that the lru lock is an innermost one, we never hold it at any caller, so the lock cost can now be avoided. We already have well working lazy dcache LRU, so it should be fine to defer LRU manipulations to scan time. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce dcache_inode_lockNick Piggin2011-01-071-12/+12
| | | | | | | dcache_inode_lock can be avoided in d_delete() and d_materialise_unique() in cases where it is not required. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce locking in d_allocNick Piggin2011-01-071-2/+4
| | | | Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache reduce dput lockingNick Piggin2011-01-071-29/+23
| | | | | | | It is possible to run dput without taking data structure locks up-front. In many cases where we don't kill the dentry anyway, these locks are not required. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache avoid starvation in dcache multi-step operationsNick Piggin2011-01-071-14/+42
| | | | | | | | Long lived dcache "multi-step" operations which retry on rename seq can be starved with a lot of rename activity. If they fail after the 1st pass, take the rename_lock for writing to avoid further starvation. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache remove dcache_lockNick Piggin2011-01-0740-307/+109
| | | | | | dcache_lock no longer protects anything. remove it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: Use rename lock and RCU for multi-step operationsNick Piggin2011-01-075-30/+152
| | | | | | | | | | | | | | | | | | | | | The remaining usages for dcache_lock is to allow atomic, multi-step read-side operations over the directory tree by excluding modifications to the tree. Also, to walk in the leaf->root direction in the tree where we don't have a natural d_lock ordering. This could be accomplished by taking every d_lock, but this would mean a huge number of locks and actually gets very tricky. Solve this instead by using the rename seqlock for multi-step read-side operations, retry in case of a rename so we don't walk up the wrong parent. Concurrent dentry insertions are not serialised against. Concurrent deletes are tricky when walking up the directory: our parent might have been deleted when dropping locks so also need to check and retry for that. We can also use the rename lock in cases where livelock is a worry (and it is introduced in subsequent patch). Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: increase d_name lock coverageNick Piggin2011-01-071-2/+12
| | | | | | | Cover d_name with d_lock in more cases, where there may be concurrent modification to it. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: scale inode alias listNick Piggin2011-01-079-9/+78
| | | | | | | Add a new lock, dcache_inode_lock, to protect the inode's i_dentry list from concurrent modification. d_alias is also protected by d_lock. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache scale subdirsNick Piggin2011-01-0716-160/+339
| | | | | | | | | | | | Protect d_subdirs and d_child with d_lock, except in filesystems that aren't using dcache_lock for these anyway (eg. using i_mutex). Note: if we change the locking rule in future so that ->d_child protection is provided only with ->d_parent->d_lock, it may allow us to reduce some locking. But it would be an exception to an otherwise regular locking scheme, so we'd have to see some good results. Probably not worthwhile. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache scale d_unhashedNick Piggin2011-01-0710-54/+102
| | | | | | | Protect d_unhashed(dentry) condition with d_lock. This means keeping DCACHE_UNHASHED bit in synch with hash manipulations. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache scale dentry refcountNick Piggin2011-01-0721-69/+126
| | | | | | | | Make d_count non-atomic and protect it with d_lock. This allows us to ensure a 0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when we start protecting many other dentry members with d_lock. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache scale lruNick Piggin2011-01-071-28/+84
| | | | | | | | Add a new lock, dcache_lru_lock, to protect the dcache LRU list from concurrent modification. d_lru is also protected by d_lock, which allows LRU lists to be accessed without the lru lock, using RCU in future patches. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache scale hashNick Piggin2011-01-072-44/+64
| | | | | | | Add a new lock, dcache_hash_lock, to protect the dcache hash table from concurrent modification. d_hash is also protected by d_lock. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* hostfs: simplify lockingNick Piggin2011-01-073-17/+24
| | | | | | | | | | Remove dcache_lock locking from hostfs filesystem, and move it into dcache helpers. All that is required is a coherent path name. Protection from concurrent modification of the namespace after path name generation is not provided in current code, because dcache_lock is dropped before the path is used. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: change d_hash for rcu-walkNick Piggin2011-01-0725-51/+94
| | | | | | | | | Change d_hash so it may be called from lock-free RCU lookups. See similar patch for d_compare for details. For in-tree filesystems, this is just a mechanical change. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: change d_compare for rcu-walkNick Piggin2011-01-0723-157/+242
| | | | | | | | | | | | | Change d_compare so it may be called from lock-free RCU lookups. This does put significant restrictions on what may be done from the callback, however there don't seem to have been any problems with in-tree fses. If some strange use case pops up that _really_ cannot cope with the rcu-walk rules, we can just add new rcu-unaware callbacks, which would cause name lookup to drop out of rcu-walk mode. For in-tree filesystems, this is just a mechanical change. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: name case update methodNick Piggin2011-01-074-31/+37
| | | | | | | smpfs and ncpfs want to update a live dentry name in-place. Rather than have them open code the locking, provide a documented dcache API. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* jfs: dont overwrite dentry name in d_revalidateNick Piggin2011-01-071-8/+35
| | | | | | | | Use vfat's method for dealing with negative dentries to preserve case, rather than overwrite dentry name in d_revalidate, which is a bit ugly and also gets in the way of doing lock-free path walking. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* cifs: dont overwrite dentry name in d_revalidateNick Piggin2011-01-071-19/+24
| | | | | | | | Use vfat's method for dealing with negative dentries to preserve case, rather than overwrite dentry name in d_revalidate, which is a bit ugly and also gets in the way of doing lock-free path walking. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: change d_delete semanticsNick Piggin2011-01-0722-42/+47
| | | | | | | | | | | | Change d_delete from a dentry deletion notification to a dentry caching advise, more like ->drop_inode. Require it to be constant and idempotent, and not take d_lock. This is how all existing filesystems use the callback anyway. This makes fine grained dentry locking of dput and dentry lru scanning much simpler. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: dcache documentation cleanupNick Piggin2011-01-071-12/+6
| | | | | | | Remove redundant (and incorrect, since dcache RCU lookup) dentry locking documentation and point to the canonical document. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* config fs: avoid switching ->d_op on live dentryNick Piggin2011-01-071-8/+9
| | | | | | | | | Switching d_op on a live dentry is racy in general, so avoid it. In this case it is a negative dentry, which is safer, but there are still concurrent ops which may be called on d_op in that case (eg. d_revalidate). So in general a filesystem may not do this. Fix configfs so as not to do this. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* cgroup fs: avoid switching ->d_op on live dentryNick Piggin2011-01-071-5/+22
| | | | | | | | | Switching d_op on a live dentry is racy in general, so avoid it. In this case it is a negative dentry, which is safer, but there are still concurrent ops which may be called on d_op in that case (eg. d_revalidate). So in general a filesystem may not do this. Fix cgroupfs so as not to do this. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* fs: use fast counters for vfs cachesNick Piggin2011-01-072-13/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | percpu_counter library generates quite nasty code, so unless you need to dynamically allocate counters or take fast approximate value, a simple per cpu set of counters is much better. The percpu_counter can never be made to work as well, because it has an indirection from pointer to percpu memory, and it can't use direct this_cpu_inc interfaces because it doesn't use static PER_CPU data, so code will always be worse. In the fastpath, it is the difference between this: incl %gs:nr_dentry # nr_dentry and this: movl percpu_counter_batch(%rip), %edx # percpu_counter_batch, movl $1, %esi #, movq $nr_dentry, %rdi #, call __percpu_counter_add # (plus I clobber registers) __percpu_counter_add: pushq %rbp # movq %rsp, %rbp #, subq $32, %rsp #, movq %rbx, -24(%rbp) #, movq %r12, -16(%rbp) #, movq %r13, -8(%rbp) #, movq %rdi, %rbx # fbc, fbc #APP # 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1 movq %gs:kernel_stack,%rax #, pfo_ret__ # 0 "" 2 #NO_APP incl -8124(%rax) # <variable>.preempt_count movq 32(%rdi), %r12 # <variable>.counters, tcp_ptr__ #APP # 78 "lib/percpu_counter.c" 1 add %gs:this_cpu_off, %r12 # this_cpu_off, tcp_ptr__ # 0 "" 2 #NO_APP movslq (%r12),%r13 #* tcp_ptr__, tmp73 movslq %edx,%rax # batch, batch addq %rsi, %r13 # amount, count cmpq %rax, %r13 # batch, count jge .L27 #, negl %edx # tmp76 movslq %edx,%rdx # tmp76, tmp77 cmpq %rdx, %r13 # tmp77, count jg .L28 #, .L27: movq %rbx, %rdi # fbc, call _raw_spin_lock # addq %r13, 8(%rbx) # count, <variable>.count movq %rbx, %rdi # fbc, movl $0, (%r12) #,* tcp_ptr__ call _raw_spin_unlock # .L29: #APP # 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1 movq %gs:kernel_stack,%rax #, pfo_ret__ # 0 "" 2 #NO_APP decl -8124(%rax) # <variable>.preempt_count movq -8136(%rax), %rax #, D.14625 testb $8, %al #, D.14625 jne .L32 #, .L31: movq -24(%rbp), %rbx #, movq -16(%rbp), %r12 #, movq -8(%rbp), %r13 #, leave ret .p2align 4,,10 .p2align 3 .L28: movl %r13d, (%r12) # count,* jmp .L29 # .L32: call preempt_schedule # .p2align 4,,6 jmp .L31 # .size __percpu_counter_add, .-__percpu_counter_add .p2align 4,,15 Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* vfs: revert per-cpu nr_unused counters for dentry and inodesNick Piggin2011-01-072-21/+12
| | | | | | | | | | | | | | The nr_unused counters count the number of objects on an LRU, and as such they are synchronized with LRU object insertion and removal and scanning, and protected under the LRU lock. Making it per-cpu does not actually get any concurrency improvements because of this lock, and summing the counter is much slower, and incrementing/decrementing it costs more code size and is slower too. These counters should stay per-LRU, which currently means global. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
OpenPOWER on IntegriCloud